A method for prefabricating and welding and air tightness testing of a refrigeration pipeline of a cold storage

Abstract

The present application relates to pressure pipeline air tightness detection technical field, and disclose a kind of cold storage refrigeration pipeline prefabrication welding and air tightness test method;For solving the problem that stable, repeatable, traceable qualification and threshold quantization of small leakage cannot be achieved in traditional method;The method, first determine boundary data unit and valve position isolation check, access dry nitrogen, reference cavity, double pressure link and near and far end temperature measuring point, initial parameter record;Pipe link and valve position switching self-check are completed under the working condition of reference cavity;Precharge and target pressure are staged inflation, and pressure temperature threshold value is gated to stabilize voltage;Main pressure maintaining period synchronously obtains the pressure temperature data of section to be detected and reference cavity, and periodically rechecks cross verification drift, triggers condition according to partition single valve single step isolation recheck, obtains small leakage stable repeatable traceable determination conclusion.

Description

Technical Field

[0001] This invention relates to the field of pressure pipeline airtightness testing technology, specifically a method for prefabricated welding and airtightness testing of cold storage refrigeration pipelines. Background Technology

[0002] The piping of a cold storage refrigeration system typically includes liquid supply pipes, return pipes, exhaust pipes, and valves and fittings. After the prefabrication and welding of the piping is completed, an airtightness test is required to determine whether there are any leaks at the welds and connections. This prevents rework and safety accidents caused by leaks during subsequent vacuuming, refrigerant charging, and commissioning. Currently, nitrogen pressure testing is commonly used on-site. This involves introducing nitrogen or a mixture of test gases into the testing pipeline to a set pressure and holding it there. The pressure change after holding the pressure is used to determine whether the system passes the test.

[0003] For example, the published invention patent application CN104075106B provides a control method and control device for a nitrogen-filling, pressure-holding, and vacuuming equipment, which controls the detection operation through processes such as nitrogen filling, pressure holding, and vacuuming. The published invention patent application CN110095237B provides a leak detection method for a refrigeration system, which combines steps such as primary vacuuming, vacuum pressure holding, filling with detection gas, leak detection using a suction gun, pressure holding test, and secondary vacuuming to complete the leak detection operation. These solutions all use pressure changes during the pressure holding stage as the basis for judgment, or locate leaks using leak detection tools.

[0004] However, during on-site nitrogen-filling and pressure-holding tests of refrigeration pipelines in cold storage facilities, pressure changes are not caused by leaks in the tested object. This is because the ambient temperature at the cold storage refrigeration pipeline site changes with the state of the gas being filled, influenced by day and night cycles, fan start-up and shutdown, and sunlight, causing pressure fluctuations unrelated to leaks. Furthermore, long pipe sections and multiple branches result in uneven temperature fields and significant thermal inertia. Local temperature changes lag, causing pressure signal delays and rebounds, leading to inconsistent test results across different pipelines at different times. Secondly, zero-point drift of pressure sensors and errors in the acquisition link cause the drift to be superimposed on the pressure difference, making it difficult to distinguish between minute leaks and instrument drift. Then, micro-leakage in inspection connectors, quick couplings, and hoses themselves can introduce leakage channels unrelated to the tested object, resulting in pressure attenuation from unknown sources. These factors unrelated to the tested object cause pressure change signals to overlap with actual minute leak signals, making it difficult to achieve stable, repeatable, and traceable acceptance and threshold quantification of minute leaks without disassembling the system and introducing additional contamination. This leads to misjudgments, missed judgments, repeated pressurization and retesting, and loss of control over delivery cycles. Therefore, an improved method is needed for nitrogen-pressurized airtightness testing of refrigeration pipelines in cold storage. This method aims to suppress or eliminate the influence of temperature fluctuations, thermal inertia, instrument drift, and leaks in the test pipes on the judgment, enabling high-confidence judgment and traceable recording of minor leaks, and achieving stable test results with controllable location and verification costs. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for prefabricated welding and airtightness inspection of refrigeration pipelines in cold storage, which solves the problems of traditional methods in achieving stable, repeatable, traceable qualification judgment and threshold quantification for minor leaks.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for prefabricated welding and airtightness testing of refrigeration pipes in cold storage, comprising:

[0008] S1: Obtain the boundary of the section to be inspected and complete valve position isolation, connect the dry nitrogen supply link, reference chamber, two pressure measurement links and temperature measurement points, and record the initial parameters;

[0009] S2: Connect the reference cavity to perform a self-test of the pipe connection and valve position switching. After the self-test passes, switch to the inspection section.

[0010] S3: Inflate in stages according to pre-charge pressure and target detection pressure, and perform pressure stabilization between stages. The pressure stabilization ends when the pressure change does not exceed the threshold and the temperature change does not exceed the threshold.

[0011] S4: During the main pressure holding period, the pressure and temperature data of the section to be inspected and the reference cavity are collected synchronously. Periodic re-verification of the connection and cross-verification of the link are performed and judged according to the consistency condition.

[0012] S5: When the verification conditions are met, perform zone isolation verification, switch valve positions according to zone order and repeat pressure holding and verification, and record test data.

[0013] Preferably, the boundary of the section to be inspected is obtained and valve position isolation is completed. The dry nitrogen supply link, reference chamber, two pressure measurement links and temperature measuring points are connected, and the initial parameters are recorded, including:

[0014] Establish boundary data sheets and complete valve position isolation. Two people verify the valve position to generate a valve position status code. If there is no valve position indication, perform blind cap sealing or replace the indicator.

[0015] The gas supply link is equipped with a filter and dryer, and the pressure difference between the gas supply side and the side to be tested is used for verification.

[0016] Connect to the reference cavity, two pressure links, and near- and far-end temperature measurement points. Update the initial parameter table version number when the measurement points change.

[0017] Preferably, the connection to the reference cavity performs a self-test on the pipe connection link and a self-test on the valve position switching, including:

[0018] After the reference cavity is connected, the self-test of the control link is performed and the connection is changed, and the main pressure meets the verification trigger caliber, a partition boundary table and a verification plan are generated.

[0019] Switch the zone valve position step by step using a single valve. After switching, wait for the pressure disturbance to decay before performing zone pressure stabilization and zone pressure holding and performing cross verification.

[0020] Preferably, after passing the self-inspection, the section to be inspected includes:

[0021] After the self-inspection is passed and the pressure measuring port of the inspection section is changed, the zonal isolation review is performed, and the zonal review pressure and the zonal allowable difference threshold are frozen.

[0022] When any partition meets the non-environment-driven trigger criteria, the review of the remaining partitions is terminated and a partition review record and a final test record are generated.

[0023] Preferably, inflation is performed in stages according to pre-charge pressure and target detection pressure, including:

[0024] When inflating according to the pre-charge pressure and the target detection pressure, an inflation scheme table is generated and the upper limit of the two-level inflation rate, the length of the stabilization window, the maximum stabilization time, the safety threshold, and the upper limit of the depressurization rate are frozen.

[0025] When the pressure drop within the significant leakage trigger window exceeds the significant leakage pressure drop threshold, the pressure increase is stopped and the partition review pending information is written.

[0026] Preferably, interstage voltage stabilization is performed, and the stabilization ends when the pressure change does not exceed a threshold and the temperature change does not exceed a threshold, including:

[0027] When interstage pressure stabilization is performed, the pressure stabilization termination condition is that the difference between the maximum and minimum pressure values ​​within the last length of the pressure stabilization period is not greater than the pressure change threshold, and the difference between the maximum and minimum temperature values ​​at the near end and the far end is not greater than the temperature change threshold.

[0028] Based on the reference cavity direction determination and difference limit record mark and early warning start time stamp, the main pressure holding task sheet references this timestamp and event code enumeration value.

[0029] Preferably, during the main pressure holding period, pressure and temperature data of the section under test and the reference cavity are collected simultaneously, including:

[0030] During the main pressure holding period, when the pressure and temperature data of the section to be inspected and the reference cavity are collected simultaneously, a pressure holding task sheet is generated. The task sheet must at least set the main pressure holding duration, sampling cycle, judgment window length, and verification cycle.

[0031] Establish a time series recording table, which should at least include the sampling time, readings of the two pressure links, reference chamber pressure reading, near-end temperature, far-end temperature, valve position status code, stage status code, and sampling quality marker.

[0032] When the sampling quality marker meets the preset abnormal conditions, record the evidence interruption marker.

[0033] Preferably, periodic takeover verification and link cross-verification are performed, determined based on consistency conditions, including:

[0034] When performing periodic takeover verification and link cross-verification, the pressure measurement link is switched to the reference cavity according to the verification cycle and the cross-verification duration is maintained. Then, it is switched back to the section to be inspected and enters the back-switching stable section.

[0035] The verification is performed based on the verification threshold and the drift threshold. If the verification fails, the verification review, link maintenance and reference cavity short-range verification are performed in sequence, and the window count is reset.

[0036] A window determination table is generated based on temperature consistency, reference consistency, and link consistency, and then written into the review trigger criteria.

[0037] Preferably, when the review conditions are met, a partitioned isolation review is performed, including:

[0038] When the review conditions are met, the partition isolation review is performed, a partition boundary table and a review plan table are generated, and the partition review pressure, stabilization window, holding time, allowable difference threshold and review cycle are frozen.

[0039] The starting point for verifying evidence is the start and end timestamps of the trigger window.

[0040] Preferably, the valve position is switched according to the zone sequence, and the pressure holding and verification are repeated, and the test data is recorded, including:

[0041] When switching valve positions according to the zone sequence and performing zone pressure holding and verification, the valve position switching is performed step by step for each valve, and the valve position status code and switching time are recorded.

[0042] After the valve position is switched, it passes through the waiting section and enters the pressure stabilization gate to perform reference chamber verification and dual pressure link drift verification.

[0043] When a partition that meets the non-environment-driven trigger criteria is found, the review of the remaining partitions is terminated, and a partition review record and a final test record are generated.

[0044] Compared with the prior art, the present invention provides a method for prefabricated welding and airtightness testing of refrigeration pipes in cold storage, which has the following beneficial effects:

[0045] 1. This invention uses a dual-person verification system of boundary data sheets and valve positions to solidify the isolation status and verify the differential pressure difference limit of the filter drying gas supply link. Under the reference chamber operating conditions, it employs self-inspection of the pipe link and valve position switching verification to distinguish non-tested channel factors such as quick connectors, hoses, and minor leaks in the pipes. During staged inflation and interstage pressure stabilization, it introduces near-end and far-end temperature synchronous gating, combining the direction of pressure change and differential limit of the reference chamber to distinguish environmental disturbances, thermal disturbances, and suspected leaks. The main pressure holding synchronously collects pressure and temperature data of the section under inspection and the reference chamber, performs pipe verification and dual-pressure link cross-verification on a periodic basis, constrains sensor drift, and outputs auditable judgment results according to window consistency gating. When the verification condition is triggered, it performs single-valve single-step isolation partition verification according to the partition boundary table to form a partition-level evidence chain, converges the scope of doubts, and achieves stable, repeatable, and traceable high-confidence judgment of minor leaks. This solves the problem of difficulty in achieving stable, repeatable, and traceable qualified judgment and threshold quantification of minor leaks in traditional methods.

[0046] 2. This invention, by associating detection session numbers with boundary data sheets, valve position verification records, task sheets, and time series records, unifies the preparation, collection, verification, and judgment criteria and continuous evidence chain. A reference cavity is used as the standard reference cavity for verification under the same operating conditions, enabling issues such as pipe seal degradation and sensor drift to be identified and addressed according to the verification cycle, avoiding misjudgments of link anomalies as leaks in the inspected section. Based on near-end and far-end temperature consistency and reference consistency gating, the invention marks the common disturbance windows of fan start / stop, sunlight, and thermal inertia, and rules exclude these from valid judgment or verification trigger counts. When the trigger criterion is reached, partitioned isolation verification is performed, with single-valve single-step switching and pressure stabilization gating constraining valve position movement disturbances, outputting reproducible and auditable detection conclusions and retest closed-loop records. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the process for prefabricated welding and airtightness inspection of refrigeration pipelines in cold storage according to the present invention. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] Example 1: Figure 1 A method for prefabricated welding and airtightness testing of refrigeration piping in cold storage is presented, including:

[0050] S1: Obtain the boundary of the section to be inspected and complete valve position isolation. Connect the dry nitrogen supply link, reference chamber, two pressure measurement links, and temperature measurement point. Record the initial parameters. The specific implementation is as follows:

[0051] Using the circuit to be inspected in the refrigeration piping of the cold storage as the test area, before the self-inspection of the pipe link, boundary modeling of the section to be inspected and initialization of the test session are performed; on site, without disassembling the pipeline and opening the system ports, a boundary data sheet for the section to be inspected and a test session number are generated based on the prefabrication list, valve station layout diagram and valve nameplates. This data sheet is used to associate the boundary data sheet, valve position verification record, consumable replacement record and initial parameter table; the boundary data sheet is stored in structured fields and the fields are fixed. It should at least include the following fields: project identifier, circuit identifier, section number, pipe section identifier list, valve identifier list, isolation valve position target value, design pressure, planned test pressure, expected volume, target value of dew point of the test medium, allowable range of ambient temperature, upper limit of allowable test duration, upper limit of allowable number of verifications, pressure test port identifier and selection basis, etc.

[0052] Section numbering uses an incremental coding system and corresponds to the physical location of the valve station; the design pressure is taken from the design documents or equipment nameplate; the planned test pressure, without exceeding the design pressure, is taken as 80% to 100% of the design pressure, and can also be selected from the commonly used engineering range of 1.6MPa to 2.5MPa, such as 2.0MPa. The value is based on the pressure rating determined in the design documents and the on-site inspection safety margin requirements; the estimated volume is obtained by converting the pipe diameter and length specified in the prefabrication list. When there are data gaps, estimation is made based on the upper limit of the same diameter and length, and the estimation method is recorded in the boundary data sheet. The value is based on the prefabrication list and the statistical results of the on-site pipe sections; the test medium is dry nitrogen. The target dew point value for the gas is between -40°C and -70°C, for example, -50°C. This value is based on the on-site gas supply drying level or medium quality certification documents and is written into the value basis field as a fixed option. The allowable ambient temperature range is expressed by both the absolute temperature range and the fluctuation range per unit time, ranging from 5°C to 35°C with a change of no more than 2°C per hour. This value is based on the on-site environmental monitoring records and the temperature threshold caliber for subsequent pressure stabilization and main pressure holding stages. The maximum allowable testing time is between 6 hours and 8 hours, and the maximum allowable number of reviews is 3 times. This value is based on the on-site delivery window, operational safety requirements, and valve position switching risk control constraints and is frozen in the boundary data sheet.

[0053] After completing the boundary data sheet, valve position isolation is performed. Isolation targets include non-inspected branches, equipment ports, vent ports, and temporary bypass ports. Isolation actions are implemented by comparing each valve identification with the target value of the isolated valve position. Valve position isolation involves dual-person verification and the generation of a valve position verification record. This record includes at least the valve identification, target valve position, actual valve position, verification method, verification time, verification personnel, and valve position status code. The valve position status code is a code generated by combining the valve identification and the target valve position, and is frozen within the current testing session. When a valve position change occurs, a new valve position status code is generated, and the valve position verification record is updated. Existing valve position status codes are retained and recorded as historical statuses. The verification passes when at least one of the valve's scale indication or limit indication matches the target valve position; if the valve has no indication or is malfunctioning, it enters a boundary anomaly branch. Boundary anomaly branch handling actions include temporary blind cap sealing or replacement of the valve position indicator. After handling, a verification is performed to generate a valve position status code. If the verification fails, the gas supply link and measurement link are not connected.

[0054] After valve isolation is successful, connect the dry nitrogen supply link. The supply link uses a detachable connection to connect to the selected pressure test port or main maintenance port, and connects the filter unit and the drying unit in series in the supply link. The filtration accuracy is no greater than 5μm. The replacement threshold for the drying unit is a dual threshold of cumulative filling volume and cumulative usage time. For example, replacement is performed when the cumulative filling volume reaches 1000 standard liters or the cumulative usage time reaches 7 days. The consumable replacement record should include at least the filter element number, drying unit number, replacement time, operator identification, and test session number, which are used to establish a traceable association with subsequent test data. After the supply link is connected, open the supply valve to a stable supply state, collect the pressure readings on the supply side and the pressure readings on the side to be tested, and calculate the difference between the two. The judgment is based on the pressure difference limit. The pressure difference limit is defined as the supply valve being open and the supply link being in a stable supply state. In this state, the upper limit of the stable difference between the supply side pressure and the pressure to be tested is between 0.02MPa and 0.10MPa, for example, 0.05MPa. The basis for this value is that under the condition that the filter and drying unit is unobstructed and the valve is open, the pressure drop caused by the throttling loss of the supply link and the local resistance of the joint should be within a small range. Exceeding this difference limit usually corresponds to abnormalities such as link blockage, joint not open, or valve not open. When the difference exceeds the pressure difference limit, the abnormality handling is prepared. The handling actions can be selected as verifying the consistency between the valve position verification record and the current valve position, checking the joint opening status, replacing the blockage consumables or reconnecting the joint, and the pressure difference value is re-collected for verification after the handling is completed. If the pressure difference limit is still not met after verification, the current detection session is terminated and a termination reason code is output. The termination reason code includes at least the type fields such as link blockage, joint not open, and valve not open.

[0055] Next, the reference chamber, two pressure measurement links, and temperature measurement points are connected and initialized. The reference chamber is only bound by the connection number and is not pressurized. The reference chamber number corresponds to the pipe assembly number and is written into the initial parameter table as a reference for subsequent self-inspection task sheets and verification records, so as to avoid the inability to trace due to component replacement or mixed numbering.

[0056] The pressure measurement link is set up as two independent measurement paths, each bound to parameters such as sensor number, range, accuracy class, and sampling period. The range is 0 to 4 MPa, the accuracy class is not lower than 0.5, for example, 0.2; the sampling period is 2 to 10 seconds, for example, 5 seconds. The range values ​​are chosen to cover the planned pressure range and allow for a safety margin, the accuracy class is chosen to meet the resolution requirements for small pressure drop detection, and the sampling period is chosen to maintain the continuity and verifiability of the pressure-temperature curve under the premise of controllable data volume.

[0057] The pressure test port can be a valve station pressure test port or a main maintenance port. If there are multiple candidate pressure test ports, they should be selected according to the number of valves connected in series. The number of valves connected in series is the number of valves connected in series between the pressure test port and the main line of the section to be inspected. If the number of valves connected in series is greater than 2, the pressure test port should be replaced or a temporary pressure test interface should be added. The identification of the pressure test port, the comparison results of the candidate ports and the selection basis should be recorded in the boundary data sheet. The reference value is to reduce the pressure uncertainty caused by valve internal leakage and additional throttling, and to reduce the impact of the pressure test channel on the airtightness judgment.

[0058] At least two temperature measuring points should be set, one near the end and one far from the section to be inspected. The far end can be a pipe section near the pressure measuring port, and the near end can be the end of the main line closest to the pressure measuring port, which is still within the same section to be inspected, or the end of a branch. If the straight length of the section is less than 10m, the far end can be the end of at least one branch bifurcation point from the pressure measuring port. The measuring point number and installation location description should be written into the initial parameter table, which should include at least the measuring point number, installation location description, installation time, and installer information, and should remain unchanged during the inspection session. If changes or moves are necessary, the parameter change branch should be entered. The parameter change branch should at least update the measuring point number and location description, generate a new initial parameter table version number, mark it as obsolete, and reset the start time of subsequent judgment records to the effective time of the new version. The old version data is only used for traceability and is not used for subsequent judgment conclusions. The above branch values ​​are mainly to avoid inconsistent temperature baselines due to different measuring point locations, which would affect the comparability and consistency of pressure-temperature correlation.

[0059] After completing the access and numbering, an initial parameter table is generated as the zero-time reference storage for the detection session. The initial parameter table should include at least the following fields: ambient temperature, ambient humidity, initial temperature of each temperature measuring point, initial pressure readings of the two pressure measurement links, pressure readings of the reference chamber in the uninflated state, current valve position status code, pressure difference between the supply side and the side under test, pipe assembly number, seal batch, operator identification, etc. After the pressure reading of the reference chamber in the uninflated state is recorded and marked as consistent with the ambient air pressure, the sampling quality is checked.

[0060] The preparation phase time should not exceed 30 minutes, for example, 30 minutes. The time is based on the drift control requirements of the on-site operation window and environmental conditions. If the time exceeds this value, the valve position verification record and the pipe fastening status should be reviewed, and the initial parameter table version number should be updated before entering the pipe link self-check of the reference cavity condition.

[0061] S2: Connect the reference cavity to perform a self-test of the pipe connection link and a valve position switching self-test. After the self-test passes, switch to the reference inspection section. The specific implementation is as follows:

[0062] Restore the frozen state of boundary data sheets, valve position verification records, and initial parameter tables in the testing session. Switch the connection to the reference chamber and perform self-tests on the piping links and valve position switching. After the self-tests are complete, switch the pressure measurement port of the section under test. The reference chamber is the only object under test. Switch the piping assembly and the two pressure measurement links to the inlet of the reference chamber. The reference chamber is a sealed chamber used during testing, with a volume typically ranging from 1L to 10L; for example, 5L, chosen to account for low thermal inertia and pressure stability requirements under on-site portability conditions. The pressure resistance is 1.5 times the planned testing pressure, based on a safety margin. The quick connector model at the reference chamber inlet matches the pressure measurement port of the section under test. The ports are identical, and the seals are of the same specification and can be selected from the same batch to ensure that the connection conditions of the reference cavity and the section under inspection are the same and to reduce the uncertainty caused by assembly differences. The self-inspection record should be filled with related fields such as reference cavity number, connector assembly number and seal batch. The self-inspection record should at least include fields such as test session number, self-inspection sequence number, reference cavity number, connector assembly number, seal batch and reconnection mark. The self-inspection sequence number is increased by one for each handling review. When a replacement action occurs, the related fields of the self-inspection record and the consumable replacement record should be updated synchronously in the handling review record, and the correspondence before and after the change should be retained to ensure that the record association is consistent with the actual link.

[0063] The self-inspection task is solidified into a self-inspection task sheet. The self-inspection task must include at least the following fields: self-inspection pressure, self-inspection duration, short window length, long window length, allowable pressure drop in the short window, allowable pressure drop in the long window, pressure stabilization window, pressure stabilization end length, pressure stabilization temperature threshold, pressure stabilization pressure threshold, upper limit of inflation rate, valve position switching sequence, valve position combination holding time, pressure relief valve small opening diameter, pressure relief valve small opening holding time, jump threshold, jump judgment caliber, link difference threshold, link difference judgment caliber, upper limit of number of reviews, and record number. The values ​​of each field are frozen in the self-inspection task sheet, the judgment caliber of self-inspection is consistent across different batches, and the records are reproducible.

[0064] The self-test pressure is set at 50% to 80% of the planned test pressure, for example, 70%. This value is chosen because micro-leakage is more easily detected at higher pressure platforms, while avoiding unnecessary risks introduced by frequently approaching the pressure limit of the reference cavity. The self-test duration is set at 30 to 90 minutes, for example, 45 minutes. This value is chosen to cover common timescales of seal rebound and initial heat exchange and to match the field operation window. The short window length is set at 3 to 10 minutes, for example, 5 minutes, with a permissible pressure drop of no more than 2000 Pa. The long window length is set at 30 to 90 minutes, for example, 45 minutes, with a permissible pressure drop of no more than 3000 Pa. The pressure drop statistics are calculated as the difference between the pressure readings at the beginning and end of the corresponding window, and the start and end times are indexed in the record for easy reproduction and auditing of the pressure drop statistics.

[0065] The pressure stabilization window is set to 20 min to 60 min, for example, 30 min; the final length of the pressure stabilization period is set to 5 min to 10 min, for example, 5 min; the pressure stabilization temperature threshold is set to 0.3℃ to 1.0℃, for example, 0.5℃; the pressure stabilization threshold is set to 3000 Pa to 15000 Pa, for example, 8000 Pa; the pressure stabilization switching condition is that the difference between the maximum and minimum temperature values ​​within the final length of the pressure stabilization period is not greater than the pressure stabilization temperature threshold, and the difference between the maximum and minimum pressure values ​​is not greater than the pressure stabilization pressure threshold. The condition is set such that the temperature and pressure fluctuations of the reference chamber can be repeated after the ambient temperature stabilizes within the allowable range, reducing the impact of inflation heating and initial heat exchange on pressure drop statistics. The upper limit of the inflation rate is set to not less than 60 standard liters per minute. The condition is set to limit the short-term pressure spikes during compression heating, and controllable inflation time is generated within the range of 1 L to 10 L of the reference chamber volume.

[0066] The valve position switching sequence takes at least three valve position combinations, such as the charging valve closed and the pressure relief valve closed, the charging valve closed and the pressure relief valve partially open for verification, and the charging valve closed and the reference cavity isolated. The valve position combination holding time takes 3 to 10 minutes, for example, 5 minutes. The pressure relief valve's small opening diameter is preferably expressed using an opening scale, with the opening value taking 1% to 5% of the rated opening, for example, 2%. When the valve has no opening scale, the partial opening is taken as 1% to 5% of the total knob travel, for example, 2%, or a fixed number of turns is used, representing one-eighth to one-quarter of a turn. The equivalent method used is recorded in the self-test record. The pressure relief valve's partial opening holding time takes 5 to 30 seconds, for example, 10 seconds, based on the premise that introducing identifiable valve position disturbances does not significantly change the pressure platform.

[0067] The jump threshold is set between 5000Pa and 20000Pa, for example, 10000Pa. This value is chosen to cover the upper limit of transient disturbances during valve position switching and to match sensor noise and resolution. The jump judgment caliber is the difference between the maximum and minimum pressure values ​​within the 30-120s interval after valve position switching. If this difference exceeds the jump threshold and the direction of the change is inconsistent with the valve position action logic, it is considered an abnormal jump. The link difference threshold is based on the pressure measurement link's range and accuracy level. It is set to no more than 0.5 to 1 times the allowable error of the full-scale range corresponding to the accuracy level. For example, for a range of 0 to 4MPa and an accuracy level of 0.2, the threshold is 4000Pa to 8000Pa. The link difference judgment caliber is the difference between the pressure readings of the main link and the verification link at the same sampling time. The maximum number of verifications is set to 3 times, for example, 3 times. This value is chosen to control the number of processing cycles and avoid generating invalid records under conditions of insufficient link reliability.

[0068] The self-test is performed according to the settings on the self-test task sheet, and stage markers and start and end times of each stage are added to the self-test record. Inflation adopts a speed-limited mode, and the upper limit of the inflation rate is taken from the frozen value of the self-test task sheet. After the self-test pressure is reached, the inflation valve is closed and the pressure stabilization work begins. After the pressure stabilization meets the switching conditions set in the self-test task sheet, the pressure holding statistics begin. During the pressure holding period, the reference cavity pressure and reference cavity temperature are continuously collected. The sampling period is taken from the frozen value of the initial parameter table and written into the self-test record. The sampling period value is consistent with the subsequent record of the previous test session to avoid incomparability of time series due to changes in the sampling period.

[0069] The self-inspection time series records are stored in an append-only manner. Each record includes at least the following fields: sampling time, reference chamber pressure, reference chamber temperature, main link pressure reading, verification link pressure reading, valve position status code, and sampling quality marker. The sampling quality marker is used to mark anomalies such as over-range, disconnection, unexpected jump, static, and timestamp gap. The trigger condition for the timestamp gap is more than two sampling periods, and the trigger condition for the continuous anomaly marker is three consecutive occurrences. The values ​​are determined based on the fact that the sampling period values ​​are frozen in the initial parameter table. Using a counting threshold related to the sampling period ensures consistency across different sampling period settings. After triggering the data validity review, the link difference judgment is performed first. The link difference threshold is the value frozen in the self-inspection task sheet. If the link difference exceeds the link difference threshold, the data is deemed unreliable and enters the processing review. If the link difference does not exceed the link difference threshold, the anomaly source is marked as short-term noise in the self-inspection record, and the self-inspection continues.

[0070] During the pressure holding period, valve position switching verification shall be performed by switching each valve position in the pipeline link according to the valve position switching sequence listed in the self-inspection task sheet. During the verification period, only valve positions listed in the self-inspection task sheet are allowed to be switched, and temporary bypass access or joint disassembly and assembly are not allowed. Each valve position switching time shall be recorded in the self-inspection record and coincide with the time of the pressure curve in the corresponding time period. If an abnormal jump is judged according to the self-inspection task sheet, or if either the short window pressure drop or the long window pressure drop exceeds the allowable pressure drop value, the self-inspection shall be deemed as a failure and shall proceed to the handling review.

[0071] The self-test output includes self-test records and self-test conclusions. The self-test record must include at least the following fields: self-test time, self-test pressure, short-window pressure drop statistics, long-window pressure drop statistics, pressure stabilization statistics, valve position switching sequence execution results, abnormal jump judgment results, link difference judgment results, handling actions, and verification count. Handling verification is performed sequentially to form a reproducible record. The handling sequence can be: first tightening the quick connector, then replacing the seal, and then replacing the hose or valve sealing assembly. The principle is to minimize the introduction of new assembly variables and ensure traceability of actions. Each handling operation is allowed one verification, with the principle being to avoid making the valve position and connector status untraceable after multiple operations. If the verification count exceeds the maximum limit set in the self-test task sheet, a maintenance mark will be added, and the current test session will be terminated.

[0072] When the self-test result is passed, the connection is changed to the pressure measuring port of the section to be tested. Before the change, the isolation valve of the reference cavity is closed, and the pressure in the connecting pipe assembly is controlled at a pressure platform not higher than the self-test pressure. After the change is completed, the valve position status code and the switching time are written. The valve position is kept unchanged and the data collection is resumed after 2 to 5 minutes, for example, after 3 minutes. The switching time is written into the self-test record and used as the starting time reference field of the subsequent inflation scheme table. Its value is based on the fact that after the transient disturbance introduced by the change action has decayed, the subsequent pressure stabilization and pressure holding records are connected with the same reference time.

[0073] If, after modification, the valve position status code is inconsistent with the self-inspection task sheet, the link difference judgment exceeds the link difference threshold, or the sampling quality mark triggers data validity review, the system will revert to the reference cavity operating condition and perform a short-term review. The short-term review window length is set between 10 and 20 minutes, for example, 15 minutes. The value is based on covering the common time scales of short-term seal rebound and temperature redistribution after modification, while controlling the on-site occupation time. The short-term review record should include at least the review start and end times, review window length, short-window pressure drop statistics, link difference judgment result, abnormal jump judgment result, valve position status code, and handling mark. The judgment criteria are based on the short-window allowable pressure drop, link difference threshold, and abnormal jump judgment criteria in the self-inspection task sheet. When the short-term review passes, the system enters the staged inflation and interstage pressure stabilization stage. When the short-term review fails, the system proceeds to the handling review.

[0074] S3: Inflate in stages according to pre-charge pressure and target detection pressure, with pressure stabilization performed between stages. The pressure stabilization ends when the pressure change does not exceed a threshold and the temperature change does not exceed a threshold. The specific implementation is as follows:

[0075] After the takeover link passes the self-test and is reconnected to the pressure test port of the section to be tested, it enters the stage of graded inflation and inter-stage pressure stabilization. An inflation scheme table is generated on site and the inflation port diameter of the test session is frozen. The version number of the inflation scheme table is the test session number and the scheme number. The scheme number is incremented after the parameters are re-frozen.

[0076] The inflation scheme table consists of structured fields, including pre-inflation pressure, target detection pressure, upper limit of pre-inflation rate, upper limit of target inflation rate, stabilization window length, stabilization end length, judgment window length, pressure change threshold, temperature change threshold, upper limit of difference, statistical caliber of pressure change, statistical caliber of temperature change, statistical caliber of difference, direction judgment caliber, maximum stabilization time, safety threshold, upper limit of pressure relief rate, minimum stabilization time, significant leakage trigger window length, significant leakage pressure drop threshold, statistical caliber of pressure drop, marker type, marker priority or superposition rule, extension strategy, environmental disturbance criterion, early warning start definition, pressure measurement link accuracy level reference field, event code enumeration table version number, check code type field, etc. The values ​​of pressure change threshold and difference limit are based on the allowable error range corresponding to the pressure measurement link range and accuracy level, combined with the typical thermal disturbance amplitude setting within the stabilization end length, so that the threshold magnitude is consistent with the measurement capability and the reproducibility is reliable.

[0077] The target detection pressure is determined based on the design pressure and does not exceed it, for example, 2.0 MPa; the pre-charge pressure is 30% to 60% of the target detection pressure, for example, 40%, chosen to first homogenize the gas in the pipe at a lower pressure platform and reduce the compression and temperature rise caused by a single pressurization; the upper limit of the pre-charge rate is no more than 30 standard liters per minute, and the upper limit of the target rate is no more than 60 standard liters per minute, chosen to limit the short-term pressure spikes caused by compression and temperature rise and the subsequent natural drop; the stabilization window length is 20 min to 90 min, for example, 40 min; the final stabilization period length is 5 min to 10 min, for example, 5 min; the decision window length is 5 min to 20 min, for example, 10 min, chosen to match the sampling period and the final stabilization period length and cover the fluctuation characteristics within the final stabilization period;

[0078] The pressure change threshold ranges from 3000 Pa to 15000 Pa, for example, 8000 Pa; the temperature change threshold ranges from 0.3℃ to 1.0℃, for example, 0.5℃; the temperature change threshold applies to both near and far temperature measuring points, and exceeding the limit at either measuring point indicates that the temperature has not stabilized; the difference limit ranges from 1000 Pa to 3000 Pa, for example, 1500 Pa; the statistical caliber for pressure change is the difference between the maximum and minimum pressure values ​​within the final length of the stabilization period, the statistical caliber for temperature change is the difference between the maximum and minimum temperature values ​​within the final length of the stabilization period, and the statistical caliber for difference is the difference between the pressure change in the inspected section and the pressure change in the reference cavity within the same judgment window; the pressure change is the pressure difference between the start and end points of the judgment window; the direction judgment caliber is the sign of the pressure difference between the start and end points of the judgment window, and the same direction indicates that the signs of the inspected section and the reference cavity are the same;

[0079] The maximum pressure stabilization time is set between 2 and 6 hours, for example, 3 hours; the safety threshold is set at 1.05 times the target detection pressure, based on the design pressure and on-site safety margin management requirements, combined with the overshoot limit of the pressure control valve. Once the safety threshold is reached, inflation stops and depressurization preparation begins; the upper limit of the depressurization rate is set at a pressure drop of no more than 50,000 Pa per minute, based on the response speed of pipe temperature changes and dew point control requirements under common operating conditions in cold storage sites, to avoid rapid pressure drop leading to a sudden drop in temperature and condensation; the minimum pressure stabilization time is set at 20 minutes, for example, 20 minutes, based on the requirement to retain necessary heat exchange time when a warning sign appears and to maintain consistency with the starting point of entering the main pressure holding phase;

[0080] The significant leakage trigger window length is set between 3 and 10 minutes, for example, 5 minutes; the significant leakage pressure drop threshold is set between 10,000 Pa and 50,000 Pa, for example, 20,000 Pa; the pressure drop statistical caliber is the difference in pressure readings from the start to the end of the trigger window. The reason for this value is that a large pressure drop in the pre-charge pressure platform in a short time often cannot be explained by heat exchange and is a gate condition for pre-stopping pressurization; the markings must include at least environmental disturbance markings, thermal disturbance markings, and suspected leakage warning markings. The marking priority or superposition rules are determined by the inflation scheme table. Suspected leakage warning markings take precedence over thermal disturbance markings and environmental disturbance markings. Thermal disturbance markings and environmental disturbance markings can be written sequentially.

[0081] The event code enumeration table contains preset enumeration values, including codes for temperature exceeding limits, fan operation, strong solar disturbance, personnel operation interruption, and gas supply pressure fluctuation, and the enumeration table version number is written into the record; the check code type field is the irreversible check identifier type generated by the system or the summary check value type of the field concatenation generated by the system; the check code field is generated by the record system with the file and written into the record header for cross-stage traceability consistency verification;

[0082] The graded inflation and pressure stabilization are performed according to the inflation scheme table version number, reference parameters, and caliber. The inflation and pressure stabilization record includes stage markers and the start and end times of each stage. During the pre-inflation stage, dry nitrogen is injected into the section to be inspected at the upper limit of the pre-inflation rate. Once the pressure reaches the pre-inflation pressure, the inflation valve is closed for pre-inflation and pressure stabilization. The pre-inflation and pressure stabilization ends when the pressure change within the final stabilization period does not exceed the pressure change threshold, the near-end and far-end temperature changes do not exceed the temperature change threshold, and the reference chamber temperature change does not exceed the temperature change threshold – these are the conditions for environmental synchronization verification. During pre-inflation and pressure stabilization, if the pressure drop within the significant leakage trigger window exceeds the significant leakage pressure drop threshold, a significant leakage marker is written, and pressure increase is stopped. Simultaneously, the process enters the partition review pending record. The partition review pending record should include fields such as trigger time, trigger window length, valve position status code, pressure curve segment index within the trigger window, reference chamber synchronization data segment index, inflation scheme table version number, and event code enumeration value. These fields can be used for subsequent reviews to directly reference the same evidence starting point.

[0083] After pre-charge and pressure stabilization, the system transitions to the target inflation stage. Once the target inflation rate reaches its upper limit, inflation continues until the target detection pressure is reached. At this point, the inflation valve is closed, and target pressure stabilization begins. During target pressure stabilization, a judgment window record is generated based on the judgment window length. The judgment window record includes at least the window start and end times, pressure change, near-end temperature change, far-end temperature change, reference chamber pressure change, direction judgment result, difference statistics result, event code enumeration value, and valve position status code. Furthermore, markers and branch information are written according to the threshold and statistical caliber corresponding to the inflation scheme table version number.

[0084] The trigger condition for the environmental disturbance flag is that the temperature change exceeds the temperature change threshold and the pressure change does not exceed the pressure change threshold within the judgment window. After triggering, the pressure is stabilized and the stabilization window is extended according to the extension strategy. The extension strategy is to extend the window by 10 minutes to 30 minutes each time, for example, 20 minutes. The cumulative extension value does not exceed the maximum stabilization time, and the event code enumeration value is written synchronously. The trigger condition for the thermal disturbance flag is that the pressure change exceeds the pressure change threshold and the direction is consistent. After triggering, the pressure is stabilized according to the extension strategy and the observation continues in the next judgment window until the stabilization end condition is met or the maximum stabilization time is reached.

[0085] The trigger condition for a suspected leak warning flag is the moment when the pressure change exceeds the pressure change threshold and the direction is different or the difference statistical value is greater than the difference limit. After triggering, the waiting time before entering the main pressure holding period is reduced to the minimum pressure stabilization time, and the trigger time is used as the warning start time stamp. The warning start time stamp and trigger window index are recorded in the reference fields of the inflation pressure stabilization record and the main pressure holding task sheet. Subsequent judgment windows are formed continuously from the warning start time. If the pressure stabilization end condition is not met even after the maximum pressure stabilization time is reached, a strong disturbance condition flag is written and a flag requiring review is output, along with a suggested time window. The suggested time window is set to the allowable ambient temperature range in the boundary data sheet and the on-site fan start-up and shutdown plan. Priority is given to the continuous period when the ambient temperature change is the smallest and the fan is stopped or the load is stable, such as from 20:00 on the same day to 6:00 on the next day, and this is used as an absolute time period to ensure consistent execution.

[0086] This stage's output includes inflation and pressure stabilization records, inflation scheme table version number, and record file verification codes. The inflation and pressure stabilization records must include at least the following fields: pre-charge pressure, target detection pressure, start and end times of each stage, number of stabilization windows, stabilization judgment result, maximum stabilization duration trigger status, pressure change, temperature change statistical summary, difference statistical summary, marker type and trigger conditions, warning start timestamp, valve position status code, reference cavity synchronization data index, event code enumeration value, and inflation scheme table version number. These records share the same file numbering system as subsequent records and are aligned across stages. Resource constraint values ​​are from... Pre-charging should begin within 6 hours of entering the main pressure holding phase. If it does not exceed 6 hours, the value should be based on the on-site operation window and environmental drift control requirements. If the value exceeds the specified time, the mark should be checked and the process should continue according to the recommended time window. After the target pressure stabilization meets the pressure stabilization end conditions, the pressure reading of the section to be inspected at the end of the pressure stabilization phase should be used as the main pressure holding starting pressure platform. The starting pressure platform, near-end and far-end temperature references, inflation scheme table version number, pressure change threshold, temperature change threshold, difference limit, mark priority or superposition rules, warning start time stamp, event code enumeration table version number, and other fields should be written into the main pressure holding task sheet reference.

[0087] S4: During the main pressure holding period, pressure and temperature data of the section under inspection and the reference cavity are collected synchronously. Periodic re-verification of the connecting pipe and cross-verification of the link are performed, and the results are judged based on consistency conditions. Specific implementation is as follows:

[0088] The system undergoes graded inflation and pressure stabilization, entering the main pressure holding stage after reaching the target detection pressure. Before the main pressure holding stage, a pressure holding task sheet is generated and the main pressure holding caliber is frozen. The pressure holding task sheet uses structured fields, including at least the main pressure holding time, sampling cycle, verification cycle, cross-verification time, judgment window length, environmental fluctuation monitoring window length, verification threshold, drift threshold, verification pressure drop threshold, stabilization period duration, verification trigger conditions, order of handling unreliable data, maximum number of restarts, record file number, check code type, verification pressure change statistics, drift difference statistics, and verification pressure drop statistics. The temperature change threshold, allowable difference limit, allowable difference statistics, and direction judgment caliber are obtained from the fields corresponding to the inflation scheme table version number and are consistent with the pressure stabilization frozen caliber.

[0089] The main pressure holding time ranges from 1 hour to 24 hours, for example, 6 hours; the sampling period ranges from 2 seconds to 10 seconds, for example, 5 seconds; the verification period ranges from 30 minutes to 120 minutes, for example, 60 minutes; the cross-verification duration ranges from 3 minutes to 10 minutes, for example, 5 minutes; the judgment window length ranges from 30 minutes to 120 minutes, for example, 60 minutes; the environmental fluctuation monitoring window length ranges from 20 minutes to 60 minutes, for example, 30 minutes. The above values ​​are based on the coverage of fan start-up and shutdown and short-term heat exchange disturbances, and form a stable nesting with the judgment window length; the back-cut stability period duration ranges from 1 minute to 3 minutes, for example, 2 minutes, which is used to attenuate the switching transient disturbances and unify the verification start point.

[0090] The verification threshold is set between 500 Pa and 2000 Pa, for example, 1000 Pa. The value is determined based on the short-term stability of the reference cavity, which can be used to indicate the degradation of the nozzle seal. The drift threshold is set between 300 Pa and 2000 Pa, for example, 1000 Pa. The value is determined based on the accuracy level of the pressure measurement link and the sampling noise range. The verification pressure drop threshold is set between 5000 Pa and 30000 Pa, for example, 15000 Pa. The value is determined based on the upper limit of the pressure change that can be explained by heat exchange within the corresponding judgment window length, and is bound to the judgment window length in the task sheet. The strong disturbance marking condition is set when the pressure change of the reference cavity exceeds 20000 Pa or the temperature change of the reference cavity exceeds 1.0℃ within the environmental fluctuation monitoring window length. The value is determined based on the upper limit of the typical pressure and temperature fluctuation of the reference cavity under fan start-up and shutdown and solar radiation disturbance, and is set to a gate threshold that is higher than the verification threshold by an order of magnitude.

[0091] The statistical caliber for the pressure drop verification is the pressure difference between the start and end points of the test section within the judgment window; the statistical caliber for the pressure change verification is the difference between the maximum and minimum pressure values ​​of the reference cavity during the cross-verification period; the statistical caliber for the drift difference is the difference between the pressure readings of the main link and the verification link at the same sampling time; the upper limit for the number of restarts is 2 to 3 times, for example, 2 times. If the upper limit is exceeded, a maintenance mark is written and the current session is terminated to constrain on-site occupation and the validity of evidence;

[0092] During the main pressure holding period, a time series record table is continuously written. The time series record table should include fields such as sampling time, main pressure of the section under test, check pressure of the section under test, main pressure of the reference cavity, check pressure of the reference cavity, near-end temperature, far-end temperature, reference cavity temperature, valve position status code, stage status code, and sampling quality mark. The valve position status code is used to record the connection conditions of the measurement link and can be selected to distinguish between the conditions of the section under test and the conditions of the reference cavity. The stage status code is used to record the operation stages of the measurement link and can be selected to distinguish between the main pressure holding acquisition stage, the cross-verification stage, and the back-cut stabilization stage. The sampling quality mark is used to record the sampling validity and should include at least over-range, disconnection, jump, static, and timestamp gap. When the timestamp gap is greater than 2 sampling cycles or the valve position status code is missing, an evidence interruption mark is written into the time series record table to trigger the data unreliability handling process, suspend window counting, and avoid continuing to accumulate window conclusions in the discontinuous evidence chain interval.

[0093] Periodic verification is performed without depressurization or disassembly of external connectors. Switching is completed through the switching valve group within the pipe assembly. Upon reaching the verification cycle, the valve position status code and switching time are recorded first. The selected pressure measurement link is then switched to the reference chamber condition and maintained for the cross-verification duration. The link is then switched back to the test section condition to enter the return-to-stabilization phase. After the return-to-stabilization phase ends, the return-to-stabilization time and valve position status code are recorded. The start and end times of the switching and the return-to-stabilization time are used as verification section boundary indices and written into the window judgment table. Verification judgment is performed according to the statistical caliber of verification pressure changes and the verification threshold. If the reference chamber pressure change exceeds the verification threshold during the cross-verification duration, the verification is deemed unsuccessful. Verification failure leads to the pipe reliability decrease branch, and branch handling follows the established procedures. The process is executed sequentially, starting with a re-verification. If the re-verification fails, the window count is paused and a link maintenance action is recorded. Link maintenance actions can include tightening connectors, replacing gaskets, or replacing hoses. After maintenance, the process returns to the reference cavity operating condition for short-range verification. The short-range verification window length is between 10 and 20 minutes, for example, 15 minutes. The verification threshold is set to the allowable pressure drop of 2000 Pa for the short window, which is based on the self-test task sheet. The allowable pressure drop is calculated as the pressure difference between the start and end points of the short-range verification window. After the short-range verification passes, the main pressure is restored, the window count is reset, and the process restarts. If the short-range verification fails, the number of restarts is accumulated. Once the maximum number of restarts is reached, a maintenance mark is added, and the current test session is terminated.

[0094] Link cross-verification is used to suppress the impact of single pressure sensor drift on verification conclusions and window determination. Within the same verification cycle, two pressure measurement links alternately undertake the acquisition task of the reference chamber operating condition to form paired evidence. During the verification cycle, the main link is first switched to the reference chamber operating condition via the switching valve group within the connector assembly and the cross-verification duration is maintained, while the verification link remains in the test section operating condition. After the main link switches back to the test section operating condition and enters the back-cut stable section, the verification link is switched back to the reference chamber operating condition and the cross-verification duration is maintained, while the main link remains in the test section operating condition. Drift checks are performed according to the drift difference statistical caliber and drift threshold frozen in the pressure holding task sheet. The drift difference statistical caliber is the difference between the pressure readings of the main link and the verification link at the same sampling time under the same operating condition. When the difference exceeds the drift threshold, it is judged as drift exceeding the limit. Drift exceeding the limit triggers an unreliable data branch. The branch action is to first perform a cross-verification to eliminate transient disturbances during switching. If the verification still exceeds the limit, replace the sensor corresponding to the drift exceeding the limit link or switch to the backup sensor, and reset the window count to start over. The sensor replacement record should include at least the replacement time, the identifier of the replaced link, the sensor number, the verification result, the identifier of the person performing the operation, and the record file verification code, so that the window evidence used to form the conclusion can be traced back to the state of the reliable link.

[0095] Consistency determination is performed within the determination window, generating a window determination table. The window conclusion is based on the prior gating. If the link consistency within the current determination window passes and the periodic verification passes, the window conclusion can be output. If the window conclusion cannot be output, the data is determined to be unreliable and a handling record is triggered. The temperature consistency condition uses the temperature change threshold reference field of the pressure holding task sheet. The value is that the near-end and far-end temperature changes within the determination window do not exceed the temperature change threshold. If this condition is not met, the determination window is marked as a thermal disturbance window and included in the window count that can continue to accumulate. Only the thermal disturbance mark is retained for review reference. The reference consistency condition uses the allowable difference limit reference field, allowable difference statistical caliber reference field, and direction determination caliber reference field of the pressure holding task sheet. The value is that the pressure change direction of the inspected section is consistent with the pressure change direction of the reference cavity and the allowable difference statistical caliber does not exceed the allowable difference limit. If this condition is met, it is marked as an environment-dominant window. The window does not meet the criteria for being marked as a non-environment-driven window. The window determination table uses structured fields for storage and includes at least the following fields: window start and end time, window type flag, temperature consistency status, reference consistency status, link consistency status, verification status, window conclusion, strong disturbance flag, evidence interruption flag, verification segment boundary index, referenced data segment index, and valve position status code sequence. The window conclusion includes at least three values: can continue to accumulate, needs to be verified, and evidence interrupted. The conditions for the value of "can continue to accumulate" are: link consistency passed, verification passed and not marked as a strong disturbance interval, and not marked as a thermal disturbance window. The condition for the value of "evidence interrupted" is that the evidence interruption flag is true within the window. The condition for the value of "needs to be verified" is that the verification trigger condition is met. When the strong disturbance flag is triggered, the corresponding interval is removed from the count of windows that can continue to accumulate and is not included in the count of windows triggered by verification. The strong disturbance flag and related index fields are reserved for audit playback.

[0096] If the following conditions exist for the review trigger condition value: If the window is not environment-dominated within one consecutive judgment window and the review pressure drop statistics are greater than the review pressure drop threshold, the link consistency passes and the re-verification passes; or if the window is environment-dominated within two consecutive judgment windows and the cumulative value of the review pressure drop statistics is greater than the review pressure drop threshold; the upper limit of the total number of cross-verifications and its basis are referenced by the pressure holding task sheet record fields, and the pressure holding task sheet must at least contain the upper limit of the total number of cross-verifications and its basis fields; the strong disturbance interval and the suggested retest time window are referenced by the window judgment table and the pressure holding task sheet supplementary fields, and the window judgment table must at least contain the strong disturbance marker and its interval index, and the pressure holding task sheet supplementary fields must at least contain the suggested retest time window and its basis fields; after the main pressure holding is completed, the window judgment table and the main pressure holding record file number are output, and the review trigger condition status and trigger time are written in the pressure holding task sheet, and the review plan field references the transfer to partition isolation review.

[0097] S5: When the verification conditions are met, perform zone isolation verification, switch valve positions according to the zone sequence, repeat pressure holding and verification, and record the test data. The specific implementation is as follows:

[0098] When the window judgment table meets the triggering conditions for the pressure holding task order review, a partition boundary table and a review plan table are generated for partition isolation review. The review evidence starts with the start and end timestamps of the trigger window in the window judgment table. The trigger type, pressure drop statistics, pressure drop threshold, link consistency, and review status are executed according to the reference fields of the pressure holding task order and the window judgment table.

[0099] The partition boundary table uses structured field records. The fields are fixed and increase with the version number. At a minimum, they include the partition number, partition pipe segment identifier list, boundary valve identifier list, valve position switching sequence, partition expected volume, partition verification pressure, partition stabilization window, continuous stabilization window length, partition minimum stabilization time, partition maximum stabilization time, partition pressure holding time, partition pressure change threshold, partition pressure change threshold value caliber, temperature change threshold reference field, partition temperature measurement point number list, partition temperature measurement point selection criteria, partition allowable difference threshold, partition allowable difference threshold value caliber, partition verification cycle, upper limit of partition cross-verification times, upper limit of partition cross-verification times value caliber, back-cut stabilization period reference field, partition status code, partition boundary table version number, effective time and applicable partition number, etc.

[0100] The number of zones can be 2 to 8, for example, 4. The value is based on the balance between positioning granularity and valve position operation. The expected volume of a zone is calculated from the pipe diameter and length in the boundary data sheet. If there are data gaps or the calculation is unreliable, it is estimated according to the upper limit of the same diameter and length, and marked with the estimated method field to avoid distortion of threshold grading and pressure stabilization time due to volume underestimation. The zone verification pressure is preferably the target detection pressure. When a zone contains weak parts or the pressure holding task sheet has a risk warning code, the zone verification pressure can be selected as 80% of the target detection pressure, for example, 1.6MPa. The value is based on improving the safety margin and reducing the pressure shock under valve position switching while keeping the leakage signal observable.

[0101] The zoned voltage stabilization window ranges from 10 to 40 minutes, for example, 20 minutes; the continuous voltage stabilization window length ranges from 3 to 10 minutes, for example, 5 minutes, and the value is determined based on the short-term heat exchange fallback period after covering valve position switching and matching the sampling period; the minimum zoned voltage stabilization duration ranges from 5 to 15 minutes, for example, 10 minutes, to shield against transient disturbances during switching; the maximum zoned voltage stabilization duration ranges from 40 to 120 minutes, for example, 60 minutes, to constrain waiting occupancy under environmental disturbances; the zoned pressure holding duration ranges from 30 minutes to 2 hours, for example, 60 minutes.

[0102] The zonal pressure change threshold ranges from 3000Pa to 12000Pa, for example, 6000Pa. The zonal pressure change threshold is 0.4 to 0.8 times the main pressure holding pressure change threshold and is bound to the zonal expected volume range. When the zonal expected volume is less than 50% of the main section expected volume, the smaller multiple is preferred. The basis for the selection is that the zonal volume is smaller and the thermal response is more consistent, so the pressure stabilization gate can be relatively tightened to more sensitively isolate the transient drop after valve position switching. The temperature change threshold is obtained by referencing the inflation scheme table version number, and the referenced field corresponds to the temperature change threshold field in the inflation scheme table.

[0103] The list of zone temperature measurement point numbers is selected and written from the boundary data sheet and the field layout record; the selection criteria for zone temperature measurement points include at least one temperature measurement point associated with each zone, and for zones that span long distances or contain two or more branch bifurcation points, two temperature measurement points are associated and cover both ends of the zone; the value for "spanning long distances" is defined as the length of the zone pipe section exceeding 10m to 30m, for example, 20m, and the basis for the value is that the thermal response differences within the zone due to the non-uniform temperature field need to be observed;

[0104] The permissible difference threshold for partitions is set between 500 Pa and 2000 Pa, for example, 1000 Pa. The permissible difference threshold for partitions is set to be bound to the expected volume of the partition and tightened as the expected volume of the partition decreases. The basis for the value is that the permissible difference can be tightened after the difference between the thermal response of the reference cavity and the partition decreases in order to improve the identification of non-environment-dominated signals.

[0105] The interval for zone verification is set between 20 minutes and 60 minutes, for example, 30 minutes. The value is based on shortening the positioning cycle and maintaining the frequency of monitoring the reliability of the control system. The maximum number of cross-verifications for zones is set at no more than 4 times. The maximum number of cross-verifications for zones is set at 25% of the interval pressure holding time, based on controlling the number of switching to reduce the risk of new leakage and prevent the verification switching from becoming the dominant source of disturbance. The duration of the back-cut stabilization period is referenced according to the pressure holding task sheet field. The value is based on attenuating transient disturbances after switching the reference cavity operating conditions and unifying the starting point of verification.

[0106] The review plan is used to freeze the execution order and time resource constraints. It uses structured field records and includes at least the following fields: review start time, partition execution order, maximum allowed duration for each partition, interval switching wait time, total duration limit, strong disturbance time window avoidance rules, termination conditions, delayed review conditions, output file number, and checksum type. The maximum allowed duration for each partition is the sum of the partition's maximum voltage stabilization duration and the partition's pressure holding duration, plus the interval switching wait time. The interval switching wait time is between 2 and 5 minutes, for example, 3 minutes, and is fixed in the review plan to attenuate transient pressure disturbances caused by valve position movements. The total duration limit is no more than 8 hours; exceeding this value will result in... The system triggers the delayed review condition and specifies the next time window. The next time window is written into the retest task sheet as an absolute time period. Its value is determined to avoid insufficient stability window caused by continuous operation during periods of high temperature difference. The strong disturbance time window avoidance rule references the strong disturbance mark interval index in the window judgment table. The value rule is to prioritize avoiding strong disturbance intervals when executing the voltage stabilization judgment window and key verification segment. If it cannot be avoided, a strong disturbance mark is written to distinguish data stability. The value of strong disturbance trigger frequency is when the proportion of strong disturbance windows exceeds 20% to 40% within the voltage holding time of any partition, such as 30%, or when two consecutive judgment windows are marked as strong disturbance windows. Its value is determined because an excessively high proportion of strong disturbance intervals will weaken the support of the stability window for partition adjudication.

[0107] The zonal review process involves valve position switching according to the zonal execution sequence, employing a single-change principle, where only one boundary valve is replaced per change. The switching time, valve position status code, and executor are recorded. Inter-zone switching follows the review plan, waiting for the specified interval before zonal pressure stabilization. Zonal pressure stabilization uses a dual-threshold gating system. Stabilization ends when the zonal pressure change within the continuous stabilization window does not exceed the zonal pressure change threshold, and when the temperature changes at all temperature measurement points in the zonal temperature measurement list do not exceed the temperature change threshold. Stabilization continues until the conditions are met or the maximum zonal stabilization duration is reached. If the maximum stabilization duration still does not meet the stabilization end condition, an environmental disturbance flag is added, and the process transitions to zonal pressure holding. The first judgment window is selected as the strong disturbance window and is not included in the review trigger count window. To avoid making suspected leakage judgments at unstable starting points; after the partition pressure stabilization is successful, the process transitions to partition pressure holding, simultaneously generating a time series record segment and a window determination segment for that partition; the time series record segment should include at least the following fields: sampling time, main pressure of the section under inspection, verification pressure of the section under inspection, main pressure of the reference cavity, verification pressure of the reference cavity, temperature of the partition temperature measuring point, valve position status code, stage status code, sampling quality mark, partition number, partition status code, and partition boundary table version number; the window determination segment should include at least the following fields: window start and end time, window type mark, temperature consistency status, reference consistency status, link consistency status, verification status, gating conclusion, reference data fragment index, partition number, partition boundary table version number, and termination condition mark, and should be consistent with the previous stage record;

[0108] The zonal pressure holding verification caliber and the link cross-verification caliber are the main pressure holding stage calibers. The switching of the reference cavity operating condition is completed by the switching valve group in the pipe assembly. The main link and the verification link alternately collect reference segment data in pairs. The reference fields in the pressure holding task sheet and inflation scheme table should include at least the verification threshold, drift threshold, allowable difference threshold, and direction determination caliber, which are all sources of the determination caliber for this stage. If the verification fails or the drift exceeds the limit, it should be handled in the order of handling unreliable data in the pressure holding task sheet. The conclusion of the corresponding zonal window is that the evidence is unreliable, and the adjudication of the suspected leakage zonal is suspended.

[0109] The partition determination adopts a consistency gating logic. The gating parameters are executed based on the frozen values ​​of the partition boundary table and the fields referenced in the pressure holding task sheet. The determination window length is 30 to 60 minutes, for example, 45 minutes. The value is determined based on the fact that it is not less than the environmental fluctuation monitoring window length and does not exceed half of the partition pressure holding time, so as to cover the partition thermal response process and control the location time. The cumulative pressure drop verification caliber is referenced according to the cumulative rule field in the pressure holding task sheet. The cumulative rule includes at least the cumulative window number, cumulative method, and other fields to form a consistent caliber under continuous window conditions. When a non-environment-dominated window occurs and the verified pressure drop statistical caliber exceeds the verified pressure drop threshold, and the link consistency and verification are passed, the partition is marked as a suspected leakage partition and the termination condition is triggered. The termination condition is to stop the verification of other partitions and... Generate a local confirmation task marker; the local confirmation task marker should include at least the following fields: suspected leak partition number, trigger window start and end time, referenced evidence index, boundary valve identification list, and partition boundary table version number, for reference in subsequent on-site location operations; when no partition triggers the suspected leak partition termination condition, mark the review conclusion as the entire section to be inspected needs to be retested and generate a retest task sheet; the retest task sheet should include at least the following fields: suggested retest time window, suggested fan status, suggested night window, suggested redo step identifier, retest reason code, and referenced evidence index; the suggested retest time window should prioritize avoiding strong disturbance intervals and be consistent with the allowable ambient temperature range of the boundary data sheet; the retest reason code should be represented by a fixed enumeration, such as strong environmental disturbance, valve position uncertainty, repeated failures of link verification, and continuous partition crosstalk;

[0110] Anomaly and boundary handling follow the principle of minimum new operations during the zonal review phase. Valve position misoperation is identified through valve position status codes and dual-person review records. After identification, it reverts to the previous stable valve position combination and re-executes the zone switching wait and zone pressure stabilization. The revert action is written into the anomaly event record and references the corresponding time series segment index. Valve internal leakage interference is identified through valve position disturbance review. The valve position disturbance review value is to perform a short-term opening and closing action on the boundary valve while maintaining zone isolation, lasting 5s to 30s, for example, 10s, and observe whether the pressure change shows repeatable jumps. If repeatable jumps occur, the valve is marked as suspected internal leakage and zone boundary adjustment is triggered. The partition boundary adjustment is carried out by re-dividing the partitions according to the equivalent boundary rules to bypass the valve. The version number of the partition boundary table is incremented and the old version is retained. The new version is written with the effective time and the applicable partition number. The version change record should include at least the fields of change reason, change time, affected partition number, and new and old boundary valve identification list. The pressure crosstalk caused by partition switching is controlled by the interval switching waiting time and pressure stabilization gating. If crosstalk is still marked, the pressure stabilization window of the partition is extended once, with the extension value being 10 minutes to 20 minutes, for example, 15 minutes. If crosstalk still exists after the extension, the partition is marked as needing retesting and the process is skipped to the next partition to avoid making decisions on unstable data.

[0111] Output partition review records and final test records; the partition review record should include at least the review trigger type, trigger window start and end time, partition number, partition start and end time, valve position switching sequence, window type marker, review status summary, link consistency summary, abnormal event summary, partition boundary table version number, and referenced evidence index field; the final test record should include at least the conclusion of the section to be inspected, suspected leakage partition number or retest mark, review start and end time, main pressure record file number, partition review record file number, data file check code, and referenced evidence index field.

[0112] In this embodiment, after the cold storage is installed, the section of a loop to be inspected is used as the inspection target. Boundary data sheets are generated and numbered on-site based on the prefabrication list and valve station layout. The planned inspection pressure is 2.0 MPa, the inspection medium is dry nitrogen, and the dew point is, for example, -50°C. Non-inspection branches are isolated according to the boundary data sheets, and two people verify the valve position status codes. Then, the gas supply link with a filter and drying unit is connected, along with the reference chamber, two independent pressure measurement links, and near-end and far-end temperature measurement points. Initial parameters are recorded and frozen as the zero-time reference for the session. Next, the connecting pipe assembly is switched to the reference chamber for self-testing. The self-test pressure is 70% of the planned inspection pressure. After stabilization, the pressure drop is judged based on a short window pressure drop of no more than 2000 Pa for 5 minutes and a long window pressure drop of no more than 3000 Pa for 45 minutes, interspersed with valve position switching verification and link difference verification. After the inspection is passed, the pressure inside the connecting assembly is kept constant. The connection is then switched to the section to be inspected, and the valve position is kept unchanged. After waiting for, for example, 3 minutes, data collection resumes. Then, the system is charged in two stages: 40% pre-charge and 2.0 MPa target pressure. The pressure is stabilized until the pressure and temperature changes do not exceed the threshold in the final window, and then the system enters the main pressure holding phase. For example, the main pressure holding phase lasts for 6 hours, sampling lasts for 5 seconds, and the judgment window lasts for 60 minutes. During the main pressure holding phase, the pressure and temperature data of the section to be inspected and the reference chamber are collected simultaneously. The system switches to the reference chamber for cross-verification according to the verification cycle, and the drift effect is suppressed through dual-link mutual inspection. The output window is determined based on temperature consistency, reference consistency, and link consistency. If the verification condition is triggered, a partition boundary table and verification plan are generated. Each partition is stabilized, held, and verified sequentially by single valve single-step switching. Finally, the partition verification record and test conclusion record are output, forming a traceable airtightness judgment closed loop.

[0113] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for prefabricated welding and airtightness inspection of refrigeration pipes in cold storage, characterized in that, include: S1: Obtain the boundary of the section to be inspected and complete valve position isolation, connect the dry nitrogen supply link, reference chamber, two pressure measurement links and temperature measurement points, and record the initial parameters; S2: Connect the reference cavity to perform a self-test of the pipe connection and valve position switching. After the self-test passes, change to the inspection section. After the self-test passes and the pressure measuring port of the inspection section is changed, perform a partition isolation review, freeze the partition review pressure and the partition allowable difference threshold. When any partition meets the non-environment-dominated triggering caliber, terminate the review of the remaining partitions and form a partition review record and a final test record. The reference consistency condition adopts the allowable difference limit reference field, allowable difference statistical caliber reference field and direction determination caliber reference field of the pressure holding task sheet. The value is that the pressure change direction of the inspection section is consistent with the pressure change direction of the reference cavity and the allowable difference statistical caliber does not exceed the allowable difference limit. If it meets the requirements, it is marked as an environment-dominated window; if it does not meet the requirements, it is marked as a non-environment-dominated window. S3: Inflate in stages according to pre-charge pressure and target detection pressure, and perform pressure stabilization between stages. The pressure stabilization ends when the pressure change does not exceed the threshold and the temperature change does not exceed the threshold. S4: During the main pressure holding period, the pressure and temperature data of the section to be inspected and the reference cavity are collected synchronously. Periodic re-verification of the connection and cross-verification of the link are performed and judged according to the consistency condition. S5: When the verification conditions are met, perform zone isolation verification, switch valve positions according to zone order and repeat pressure holding and verification, and record test data.

2. The method for prefabrication, welding, and airtightness inspection of refrigeration pipelines in cold storage according to claim 1, characterized in that, Obtain the boundary of the section to be inspected and complete valve position isolation. Connect the dry nitrogen supply link, reference chamber, two pressure measurement links, and temperature measuring point. Record the initial parameters, including: Establish boundary data sheets and complete valve position isolation. Two people verify the valve position to generate a valve position status code. If there is no valve position indication, perform blind cap sealing or replace the indicator. The gas supply link is equipped with a filter and dryer, and the pressure difference between the gas supply side and the side to be tested is used for verification. Connect to the reference cavity, two pressure links, and near- and far-end temperature measurement points. Update the initial parameter table version number when the measurement points change.

3. The method for prefabrication, welding, and airtightness inspection of refrigeration pipelines in cold storage according to claim 1, characterized in that, The connection to the reference cavity performs a self-test on the pipe connection and a self-test on valve position switching, including: After the reference cavity is connected, the self-test of the control link is performed and the connection is changed, and the main pressure meets the verification trigger caliber, a partition boundary table and a verification plan are generated. Switch the zone valve position step by step using a single valve. After switching, wait for the pressure disturbance to decay before performing zone pressure stabilization and zone pressure holding and performing cross verification.

4. The method for prefabrication, welding, and airtightness inspection of refrigeration pipelines in cold storage according to claim 1, characterized in that, Inflation is graded according to pre-charge pressure and target detection pressure, including: When inflating according to the pre-charge pressure and the target detection pressure, an inflation scheme table is generated and the upper limit of the two-level inflation rate, the length of the stabilization window, the maximum stabilization time, the safety threshold, and the upper limit of the depressurization rate are frozen. When the pressure drop within the significant leakage trigger window exceeds the significant leakage pressure drop threshold, the pressure increase is stopped and the partition review pending information is written.

5. The method for prefabrication, welding, and airtightness inspection of refrigeration pipelines in cold storage according to claim 1, characterized in that, Interstage voltage stabilization is performed, and the stabilization ends when the pressure change does not exceed a threshold and the temperature change does not exceed a threshold, including: When interstage pressure stabilization is performed, the pressure stabilization termination condition is that the difference between the maximum and minimum pressure values ​​within the last length of the pressure stabilization period is not greater than the pressure change threshold, and the difference between the maximum and minimum temperature values ​​at the near end and the far end is not greater than the temperature change threshold. Based on the reference cavity direction determination and difference limit record mark and early warning start time stamp, the main pressure holding task sheet references this timestamp and event code enumeration value.

6. The method for prefabrication, welding, and airtightness inspection of refrigeration pipelines in cold storage according to claim 1, characterized in that, During the main pressure holding period, pressure and temperature data of the section under test and the reference cavity are collected simultaneously, including: During the main pressure holding period, when the pressure and temperature data of the section to be inspected and the reference cavity are collected simultaneously, a pressure holding task sheet is generated. The task sheet must at least set the main pressure holding duration, sampling cycle, judgment window length, and verification cycle. Establish a time series recording table, which should at least include the sampling time, readings of the two pressure links, reference chamber pressure reading, near-end temperature, far-end temperature, valve position status code, stage status code, and sampling quality marker. When the sampling quality marker meets the preset abnormal conditions, record the evidence interruption marker.

7. The method for prefabrication, welding, and airtightness inspection of refrigeration pipelines in cold storage according to claim 1, characterized in that, Periodic takeover verification and link cross-verification are performed, determined according to consistency conditions, including: When performing periodic takeover verification and link cross-verification, the pressure measurement link is switched to the reference cavity according to the verification cycle and the cross-verification duration is maintained. Then, it is switched back to the section to be inspected and enters the back-switching stable section. The verification is performed based on the verification threshold and the drift threshold. If the verification fails, the verification review, link maintenance and reference cavity short-range verification are performed in sequence, and the window count is reset. A window determination table is generated based on temperature consistency, reference consistency, and link consistency, and then written into the review trigger criteria.

8. The method for prefabrication, welding, and airtightness inspection of refrigeration pipelines in cold storage according to claim 1, characterized in that, When the review criteria are met, a partitioned isolation review is performed, including: When the review conditions are met, the partition isolation review is performed, a partition boundary table and a review plan table are generated, and the partition review pressure, stabilization window, pressure holding time, allowable difference threshold and review cycle are frozen. The starting point for verifying evidence is the start and end timestamps of the trigger window.

9. The method for prefabrication, welding, and airtightness inspection of refrigeration pipelines in cold storage according to claim 1, characterized in that, Switch valve positions according to the zone sequence and repeat pressure holding and verification, recording test data, including: When switching valve positions according to the zone sequence and performing zone pressure holding and verification, the valve position switching is performed step by step for each valve, and the valve position status code and switching time are recorded. After the valve position is switched, it passes through the waiting section and enters the pressure stabilization gate to perform reference chamber verification and dual pressure link drift verification. When a partition that meets the non-environment-driven trigger criteria is found, the review of the remaining partitions is terminated, and a partition review record and a final test record are generated.

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