Risk evaluation method for small metal connecting pipe based on inspection correction coefficient

Abstract

The invention discloses a risk evaluation method for a small metal connecting pipe based on an inspection correction coefficient, and relates to the technical field of equipment risk evaluation, and the method comprises the steps: calculating a failure possibility factor according to the internal and external environment corrosivity, material and vibration conditions of the small metal connecting pipe; calculating a failure consequence factor according to the toxicity and flammability of a medium contained in the small metal connecting pipe and the operation temperature and the operation pressure of the small metal connecting pipe in combination with the consequence correction coefficient; introducing an inspection correction coefficient, and inspecting and correcting the risk value of the small metal connecting pipe to obtain an inspected and corrected risk value; the value of the inspection correction coefficient is related to inspection validity, inspection times and whether defects are inspected or not; and evaluating the risk of the small metal connecting pipe according to the checked and corrected risk value. The method can accurately, scientifically and objectively evaluate the risk level of the small metal connecting pipe in the container / pipeline.

Description

Technical Field

[0001] The invention relates to the technical field of equipment risk assessment, in particular to a risk assessment method for a small metal pipe of a container or pipeline. Background Art

[0002] Small metal pipes are pipes that connect the container body, pipeline main line and thermocouples, pressure gauges, drainage guides, exhaust valves, liquid level gauges, etc. They are generally within the first valve, with a diameter of less than 50mm (DN50). The medium does not flow here to form a blind end. The connection with the container body and pipeline main line is mostly a socket fillet weld structure. This part is mostly welded manually, and the quality is greatly affected by the individual factors of the welder. There are few internal quality detection methods for fillet welds, and the quality of this part is the weakest link in the manufacturing process. Therefore, due to its special position, the means and methods of inspection and testing of small metal pipes are limited, especially during the operation of the device, it is difficult to monitor and manage. In addition to the influence of internal media, operating temperature, operating pressure and internal and external environment, the safety of small metal pipes has also become the focus of attention and hidden danger inspection of the entire device. A piece of equipment (container) or a pipeline has several small metal pipes. A 5 million tons / year crude oil processing plant has thousands of small metal pipes. Large petrochemical enterprises have tens of thousands or even hundreds of thousands of small metal pipes. The management or inspection and detection of these pipes is quite difficult. It is necessary to conduct risk assessment on small metal pipes and manage them in different levels according to the assessed risk. At present, risk assessment technology is widely used in pressure equipment and pipelines, but there is no risk assessment technology for small metal pipes. Summary of the invention

[0003] In order to overcome the defects in the above-mentioned prior art, the present invention provides a risk assessment method for small metal nozzles based on inspection correction coefficient, which takes into account the failure possibility factor, failure consequence factor and inspection correction coefficient at the same time, and can comprehensively judge the risk level of small metal nozzles.

[0004] To achieve the above object, the present invention adopts the following technical solutions, including: A risk assessment method for small metal pipes based on an inspection correction coefficient, wherein the small metal pipes refer to metal pipes with a diameter smaller than a set value; the risk assessment method includes the following contents: Calculate the failure probability factor k based on the internal and external environmental corrosion, material and vibration conditions of the small metal nozzle; According to the toxicity and flammability of the medium contained in the small metal pipe, the operating temperature and operating pressure of the small metal pipe, and combined with the consequence correction coefficient, calculate the failure consequence factor h; Calculate the risk value R using the failure possibility factor k and the failure consequence factor h; Introduce the test correction coefficient β to test and correct the risk value R, and obtain the risk value R after test correctionnew ; The value of the inspection correction coefficient β is related to the inspection validity, the number of inspections and whether defects are detected; According to the risk value R after test correction new Evaluate the risk of small metal nozzles.

[0005] Preferably, the value of the inspection correction coefficient β is specifically determined as follows: If the inspection is not performed or is invalid, the inspection correction factor is β1; If the first inspection is conducted and no defects are detected, the inspection correction factor is β2; If two or more inspections are conducted and no defects are found, the inspection correction factor is β3; If defects are found during inspection and the small metal pipe has been repaired, the inspection correction factor is β4; Among them, β4>β1≥1>β2>β3; If defects are detected and the small metal nozzle is not repaired, the risk of the small metal nozzle will be directly considered to be the greatest.

[0006] Preferably, the failure probability factor k is calculated as follows: ; In the formula, t1, t2, and t3 are the corrosion score, material score, and vibration score of the small metal pipe respectively; k1, k2, and k3 are the weight coefficients of t1, t2, and t3 respectively, and k1+k2+k3=1; ∏ is the sign of the continuous product; Among them, the stronger the internal and external environmental corrosion of the small metal nozzle, the higher the corrosion score t1; the less the material of the small metal nozzle meets the process requirements, the higher the material score t2; the greater the vibration of the small metal nozzle, the higher the vibration score t3; the greater the value of the failure possibility factor k, the greater the possibility of failure.

[0007] Preferably, the internal and external environmental corrosion levels of the small metal pipe are divided into strong corrosion, certain corrosion, slight corrosion, and no corrosion, and the corresponding corrosion scores t1 are t11, t12, t13, and t14, respectively; wherein t11>t12>t13>t14>1; The classification method of the internal and external environmental corrosivity level is as follows: if the annual corrosion rate a ≥ α1 or the damage sensitivity is high, it is judged as strong corrosiveness; if the annual corrosion rate a∈[α2,α1) or the damage sensitivity is medium, it is judged as certain corrosiveness; if the annual corrosion rate a∈[α3,α2) or the damage sensitivity is low, it is judged as slight corrosiveness; if the annual corrosion rate a<α3 or the damage sensitivity is zero, it is judged as slight corrosiveness; among which, α1>α2>α3; The calculation method of the annual corrosion rate a is as follows: Assume that the minimum wall thickness of the metal pipe tested this time is s, and the minimum wall thickness of the last test is s 0 , the time difference between this test and the last test is n, a=(ss 0 ) / n; where the unit of annual corrosion rate is mm / year, the unit of wall thickness is mm, and the unit of time difference is year; The damage sensitivity is divided into four levels: high, medium, low, and none. First, determine whether the internal and external environment of the small metal nozzle has damage mechanisms such as environmental cracking, material degradation, mechanical damage, corrosion thinning or other damage, and determine the damage mechanism category of the small metal nozzle; then, based on the inspection results, determine the damage sensitivity corresponding to different damage mechanism categories.

[0008] Preferably, the material grade of the small metal pipe is divided into not meeting the process requirements and meeting the process requirements, and the corresponding material scores t2 are t21 and t22 respectively; wherein t21>t22>1; The material grades are divided as follows: if the material of the small metal pipe is inconsistent with the main material of the container or pipeline, or the material of the small metal pipe does not meet the material selection requirements, it is judged as not meeting the process requirements; if the material of the small metal pipe is consistent with the main material of the container or pipeline, and the material of the small metal pipe meets the material selection requirements, it is judged as meeting the process requirements.

[0009] Preferably, the vibration level of the small metal pipe is divided into strong vibration, weak vibration and no vibration according to the vibration frequency, and the corresponding vibration scores t3 are t31, t32 and t33 respectively; among which, t31>t32>t33>1.

[0010] Preferably, the failure consequence factor h is calculated as follows: ; Among them, C 0 Indicates the consequence correction factor; h1, h2, h3, and h4 are the toxicity score, flammability score, operating temperature score, and operating pressure score of the small metal nozzle respectively; Among them, the higher the toxicity hazard of the medium contained in the small metal pipe, the greater the toxicity score h1; the higher the flammability level of the medium contained in the small metal pipe, the greater the flammability score h2; the higher the operating temperature of the small metal pipe, the greater the operating temperature score h3; the higher the operating pressure of the small metal pipe, the greater the operating pressure score h4; the greater the value of the failure consequence factor h, the more serious the failure consequence.

[0011] Preferably, if the medium contained in the small metal pipe is an explosive medium, and the operating temperature of the small metal pipe exceeds the set temperature or the operating pressure exceeds the set pressure, then C 0 The value is δ1; if the toxicity score h1 of the small metal pipe exceeds the set value, then C 0The value is δ2; otherwise C 0 The value is δ3; where δ1>δ2>δ3≥1.

[0012] Preferably, the risk value R = k·h; the corrected risk value R new =β·R; R new The larger it is, the greater the risk of small metal takeovers.

[0013] The present invention also provides a computer program product, which includes a computer program / instruction. When the computer program / instruction is executed by a processor, the risk assessment method for small metal nozzles based on an inspection correction coefficient is implemented.

[0014] The advantages of the present invention are: (1) The present invention provides a risk assessment method for small metal nozzles based on an inspection correction coefficient, which comprehensively considers the failure possibility factor and failure consequence factor of the small metal nozzles, and realizes the inspection correction of the risk value by introducing the inspection correction coefficient. According to the inspection effectiveness, the number of inspections and the defect discovery situation, it can more truly reflect the actual risk, thereby accurately evaluating the risk level of small metal nozzles.

[0015] (2) Regarding the possibility of failure, the three core factors of internal and external environmental corrosion, material and vibration are comprehensively considered, making the evaluation of the failure possibility of small metal pipes more scientific and reasonable.

[0016] (3) In terms of the classification of internal and external environmental corrosion levels, the annual corrosion rate and damage sensitivity of small metal pipes are comprehensively considered to enhance the objectivity of the judgment.

[0017] (4) With regard to the consequences of failure, the toxicity and flammability of the medium contained in the small metal pipe as well as the operating temperature and operating pressure of the small metal pipe are comprehensively considered, and a consequence correction factor is introduced to amplify the effect for explosive media and highly toxic media, thereby increasing the severity of the consequences of failure.

[0018] (5) The present invention significantly improves the accuracy and practicality of risk assessment of small metal pipes through verification and correction mechanism, multi-dimensional quantitative evaluation and refined classification.

[0019] (6) The present invention guides the management of inspection effectiveness through the inspection correction coefficient. If there is no inspection or invalid inspection, the risk value will be increased, which will help force the implementation of the inspection plan; if the inspection is effective and there are no defects, the risk value will be reduced to verify the maintenance effect; after the defects are repaired, the risk value will be reduced to encourage timely repair behavior, which will help form a closed-loop management of "inspection-repair-re-evaluation". BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure is a flow chart of a risk assessment method for small metal nozzles based on inspection correction coefficient. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Example 1 Depend on Figure 1 As shown, a risk assessment method for a small metal nozzle based on an inspection correction coefficient of the present invention includes the following contents: According to the internal and external environmental corrosion, material and vibration conditions of the small metal nozzle, the failure possibility is evaluated and the failure possibility factor k is calculated; According to the toxicity and flammability of the medium contained in the small metal pipe, the operating temperature and pressure of the small metal pipe, and combined with the consequence correction factor C 0 , evaluate the failure consequences and calculate the failure consequence factor h; Calculate the risk value R based on the failure possibility factor k and the failure consequence factor h, R=k·h; Introduce the test correction coefficient β to test and correct the risk value R, and obtain the risk value R after test correction new , R new =β·R; the value of the inspection correction coefficient β is related to the inspection validity, the number of inspections and whether defects are detected; According to the risk value R after test correction new , determine the risk level and evaluate the risk of small metal pipes.

[0023] Factors influencing the possibility of failure include: internal and external environmental corrosion, material and vibration of the small metal pipe. The calculation method is: ; Wherein, t1, t2, t3 are the corrosion score, material score, and vibration score respectively; k1, k2, k3 are the weight coefficients of t1, t2, t3 respectively, k1+k2+k3=1; ∏ is the sign of the continuous product.

[0024] The stronger the internal and external environmental corrosion of the small metal pipe, the higher the corrosion score. In this embodiment, the internal and external environmental corrosion levels of the small metal pipe are divided into strong corrosion, certain corrosion, slight corrosion, and no corrosion, and the corresponding corrosion scores t1 are 10, 5, 2, and 1, respectively, and the weight coefficient of corrosion k1=0.5, as shown in Table 1 below.

[0025] Table 1 Classification of environmental corrosivity ; The corrosion levels of internal and external environments are divided as follows: if the annual corrosion rate a ≥ 0.508 or the damage sensitivity is high, it is highly corrosive; if the annual corrosion rate a∈[0.254,0.508) or the damage sensitivity is medium, it is somewhat corrosive; if the annual corrosion rate a∈[0.1,0.254) or the damage sensitivity is low, it is slightly corrosive; if the annual corrosion rate a≤0.1 or there is no damage sensitivity, it is slightly corrosive.

[0026] The calculation method of the annual corrosion rate a is as follows: Assume that the minimum wall thickness of the metal pipe tested this time is s, and the minimum wall thickness of the last test is s 0 (If this is the first test, then s 0 Take the nominal wall thickness), the time difference between this test and the last test is n (the time difference is calculated in years, such as 1 year and 3 months, then n=1.25 years), a=(ss 0 ) / n; where the unit of annual corrosion rate is millimeter / year (mm / y), the unit of wall thickness is millimeter (mm), and the unit of time difference is year (y).

[0027] The damage sensitivity is divided into four levels: high, medium, low, and none. First, determine whether the internal and external environment of the small metal pipe has environmental cracking, material degradation, mechanical damage, other damage, or corrosion thinning damage mechanisms to obtain the damage mechanism category of the small metal pipe; then, combined with the inspection situation, determine the damage sensitivity corresponding to different damage mechanism categories. The damage sensitivity determination is shown in Table 2 below.

[0028] Table 2 Damage sensitivity determination table ; For the description of the damage mechanisms of environmental cracking, material degradation, mechanical damage, other damage, and corrosion thinning in Table 2, please refer to GB / T30579-2022 "Damage Pattern Identification of Pressure Equipment".

[0029] Environmental cracking is mainly the influence of the internal environment, i.e. the medium contained, on the small metal pipe, and the influence of the external environment, i.e. the atmospheric environment, on the small metal pipe. For example, in the atmospheric salt spray corrosion environment in coastal areas, the external environment of the small metal pipe can constitute the first category of damage mechanism with environmental cracking damage mechanism in Table 2, while other areas will not constitute the damage mechanism of environmental cracking caused by the external environment.

[0030] The inspection of small metal nozzles includes: macroscopic inspection, ultrasonic thickness measurement, surface defect detection (magnetic particle MT or penetration PT), buried defect detection (ray RT or phased array PA); among them, for small metal nozzles of carbon steel and low alloy steel, MT is selected for surface defect detection, otherwise it is invalid; for small metal nozzles of high alloy steel such as stainless steel, PT is selected for surface defect detection, otherwise it is invalid. The specific judgment of inspection effectiveness is shown in Table 3 below.

[0031] Table 3 Test validity determination table ; The less the material of the small metal pipe meets the process requirements, the higher the material score. In this embodiment, the material grade of the small metal pipe is divided into not meeting the process requirements and meeting the process requirements, and the corresponding material scores t2 are 100 and 5 respectively, and the material weight k2=0.3. The material grade division method is shown in Table 4 below.

[0032] Table 4 Material grade classification table ;

[0033] In this embodiment, it is particularly required that the material of the small metal pipe for use in highly acidic and sulfur-containing environments above 240°C, hydrogen sulfide gas environments, high-temperature hydrogen environments, strong acid and alkali and high-temperature environments meets the material selection requirements.

[0034] The greater the vibration of the small metal pipe, the higher the vibration score. In this embodiment, the vibration level of the small metal pipe is divided into strong vibration, weak vibration, and no vibration. The corresponding vibration scores t3 are 10, 5, and 1 respectively, and the vibration weight k3=0.2. The specific division method of the vibration level is shown in Table 5 below.

[0035] Table 5 Vibration level classification table ; The factors causing the failure consequence include: the toxicity of the medium contained in the small metal pipe, the flammability of the medium contained in the small metal pipe, the operating temperature of the small metal pipe, and the operating pressure of the small metal pipe. The expression of the failure consequence factor h is: ; Among them, C 0 It represents the consequence correction factor; h1, h2, h3 and h4 are the toxicity score, flammability score, operating temperature score and operating pressure score of the small metal pipe respectively.

[0036] If the toxicity of the medium contained in the small metal pipe is extremely hazardous, then C 0 =1.2; if the medium contained in the small metal pipe is explosive medium, and the operating temperature of the small metal pipe exceeds 250℃ or the operating pressure exceeds 1.6MPa, then C 0=2.0; in other cases, C 0 =1.0.

[0037] The higher the toxicity of the medium contained in the small metal pipe, the greater the toxicity score. In this embodiment, the toxicity levels are divided into extremely hazardous, highly hazardous, moderately hazardous, slightly hazardous, and non-toxic, and the corresponding toxicity scores h1 are 50, 25, 15, 8, and 4, respectively.

[0038] The higher the flammability level of the medium contained in the small metal pipe, the greater the flammability score. In this embodiment, the flammability level is divided into Class A, Class B, Class C, and non-flammable, and the corresponding flammability scores h2 are 25, 15, 8, and 4, respectively. In addition, when the operating temperature of the small metal pipe exceeds the auto-ignition point, the flammability level is directly classified as Class A.

[0039] The toxicity and flammability categories of the medium refer to SH3501-2021 "Petrochemical Toxic and Flammable Medium Steel Pipeline Engineering Construction and Acceptance Specifications".

[0040] The categories of explosive media refer to HG / T20660-2017 "Classification Standard for Chemical Toxicity Hazards and Explosion Hazards in Pressure Vessels".

[0041] The higher the operating temperature T of the small metal pipe, the greater the operating temperature score. In this embodiment, the operating temperature T is divided into levels of T≥400°C, 250°C≤T<400°C, 100°C≤T<250°C, and T<100°C, and the corresponding operating temperature scores h3 are 25, 20, 8, and 4, respectively.

[0042] The higher the operating pressure P of the small metal pipe, the greater the operating pressure score. In this embodiment, the operating pressure P is divided into levels of P≥4MPa, 1.6MPa≤P<4MPa, 0.1MPa≤P<1.6MPa, P<0.1MPa, and the corresponding operating pressure scores h4 are 25, 20, 8, and 4 respectively.

[0043] Risk value R = k·h; test the corrected risk value R new =β·R. The larger the risk value, the higher the risk level, and the higher the risk of the small metal pipe. In this embodiment, the risk level is divided into five levels from low to high: I, II, III, IV, and V, and the corresponding risk assessments are high risk, medium-high risk, medium risk, low risk, and very low risk, respectively. The specific division method is shown in Table 6 below.

[0044] Table 6 Risk level classification table ; The inspection correction factor β is related to the inspection effectiveness, the number of inspections, and whether excessive defects are detected. Excessive defects include failure of the thinning strength check of the nozzle, surface opening defects, and buried defects that do not meet the classification requirements in TSG D7005 "Rules for Periodic Inspection of Pressure Pipelines - Industrial Pipelines".

[0045] The value of the test correction coefficient β is as follows: If the inspection is not carried out or the inspection is invalid, the inspection correction factor β=1; If the first inspection is conducted and no excessive defects are found, the inspection correction factor β = 0.5; If two or more inspections are conducted and no excessive defects are found, the inspection correction factor β = 0.3; When an excessive defect is detected, if the small metal pipe is repaired, the inspection correction coefficient β=4; if the small metal pipe is not repaired, the risk of the small metal pipe is directly regarded as the largest. In this embodiment, the risk value R after inspection correction is directly set to new ≥650, the risk level after inspection and correction is directly determined as Level V, and the risk assessment is high risk.

[0046] Example 2 The small metal pipe on the outlet separator of the acid gas compressor of a central refinery was made of 20# (HIC steel), with an operating temperature of 110°C and an operating pressure of 2.25MPa. Two effective inspections were carried out and no defects were found. The inspection methods included thickness inspection, magnetic particle MT inspection and phased array PA inspection.

[0047] The small metal pipe is located in the middle area, and the external environment does not constitute a damage mechanism for environmental cracking; however, the medium contained inside is acidic gas, containing hydrogen sulfide (H 2 S), which constitutes wet hydrogen sulfide damage to the pipeline, belongs to environmental cracking, and no damage is found during the inspection, and the sensitivity is judged to be medium. It is judged that the internal and external environmental corrosion of the small metal pipe is somewhat corrosive, t1=5.

[0048] The material of the small metal pipe is HIC-resistant steel, which basically meets the medium process requirements, t2=5.

[0049] The small metal pipe is connected to the compressor and is subject to strong vibration, t3=10.

[0050] H 2 The toxicity of S is highly hazardous, h1=25.

[0051] Contains H 2 The flammability of S's acidic gas is Class A, h2=25.

[0052] The operating temperature is 110℃, h3=8.

[0053] The operating pressure is 2.25MPa, h4=20.

[0054] The medium is not extremely hazardous or explosive. 0 =1.0.

[0055] Failure probability factor of small metal nozzle .

[0056] Failure consequence factors of small metal pipes .

[0057] Risk value of small metal pipe , the risk level is IV, and the risk assessment is medium-high risk; The metal small pipe was effectively inspected twice and no excessive defects were detected. The inspection correction coefficient β = 0.3. Therefore, the risk value R after inspection correction is new =β·R=0.3×585=175.5. The risk level after inspection and correction is III, and the risk assessment is medium risk.

[0058] According to the risk level determination table in Table 6, the risk level of the small metal pipe after inspection and correction is medium-high risk. 2 The small metal nozzles of S medium are seriously corroded in actual operation. The risk of uninspected small nozzles is high, but the risk is reduced after inspection.

[0059] Example 3 A small metal pipe of a medium-pressure steam pipeline in a central refinery was made of 20# material, with an operating temperature of 300℃ and an operating pressure of 2.5MPa. After three effective inspections, no defects were found. The inspection methods included thickness measurement, magnetic particle MT inspection and phased array PA inspection.

[0060] The small metal pipe is located in the central area, and the external environment does not constitute a damage mechanism of environmental cracking; the medium contained in the small metal pipe is steam, which causes erosion corrosion to the pipeline, which belongs to corrosion thinning, with an annual corrosion rate of 0.3mm / y, and no defects were found in the inspection, and the sensitivity is low. It is judged that the internal and external environmental corrosion of the small metal pipe is corrosive to a certain extent, t1=5.

[0061] The material of the small metal pipe is 20# steel. Since the pipe material with an operating temperature of 300℃ should be CrMo steel, it does not meet the medium process requirements, t2=100.

[0062] Low-frequency vibration was detected around the small metal pipe, which is a weak vibration, t3=5.

[0063] The medium contained in the small metal pipe, namely steam, is non-toxic and hazard-free, h1=4.

[0064] The medium contained in the small metal pipe, namely steam, is non-flammable, h2=4.

[0065] The operating temperature is 300℃, h3=20.

[0066] The operating pressure is 2.5MPa, h4=20.

[0067] The medium is not extremely hazardous or explosive. 0 =1.0.

[0068] Failure possibility of small metal pipes .

[0069] Failure consequences of small metal pipes .

[0070] Risk value of small metal pipe , the risk level is V, and the risk assessment is high risk; The metal pipe was effectively inspected three times and no excessive defects were detected. The inspection correction coefficient β = 0.3. Therefore, the risk value R after inspection correction is new =β·R=0.3×5850=1755. The risk level after inspection and correction is V, and the risk assessment is high risk.

[0071] According to the risk level determination table in Table 6, the risk level of the small metal pipe after inspection and correction is high risk, and the risk level before and after inspection and correction remains unchanged. Analysis shows that the high risk of the small metal pipe is mainly due to the material selection not meeting the process requirements of the medium.

[0072] Example 4 A small metal pipe on a nitrogen pipeline of a seaside refinery is made of 304L, with an operating temperature of 40°C and an operating pressure of 0.8MPa. During the inspection, tiny cracks were found, which were eliminated after grinding. The inspection methods include thickness measurement, penetration PT inspection and phased array PA inspection.

[0073] The medium contained in the small metal pipe is nitrogen, and there is no obvious corrosion mechanism inside. However, because it is operated at the seaside, the external environment has chloride stress corrosion cracking, which belongs to environmental cracking. The inspection found excessive cracks and high damage sensitivity. It is judged that the internal and external environmental corrosion of the small metal pipe is highly corrosive, t1=10.

[0074] The material of the small metal pipe is 304L, which basically meets the medium process requirements, t2=5.

[0075] There is no vibration source around the small metal pipe, t3=1.

[0076] Nitrogen has no toxicity, h1=4.

[0077] Nitrogen is non-flammable, h2=4.

[0078] The operating temperature is 40℃, h3=4.

[0079] The operating pressure is 0.8MPa, h4=8.

[0080] The medium is not extremely hazardous or explosive. 0 =1.0.

[0081] Failure probability factor of small metal nozzle .

[0082] Failure consequence factors of small metal pipes .

[0083] Risk value of small metal pipe , the risk level is II, and the risk assessment is low risk; The metal pipe was repaired after the defect exceeded the standard. The inspection correction coefficient β=4. Therefore, the risk value R after inspection correction is new =β·R=4×30=120, the risk level after inspection and correction is level III, and the risk assessment is medium risk.

[0084] According to the risk level determination table in Table 6, the risk level of the small metal pipe after inspection and correction is medium risk. During actual operation, the risk of the small nitrogen metal pipe is relatively low. However, due to the influence of salt spray on the stainless steel pipeline at the seaside, chloride stress corrosion cracking occurs, resulting in high damage sensitivity, thus increasing the risk level.

[0085] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A risk assessment method for small metal nozzles based on inspection correction coefficient, characterized in that: The small metal pipe refers to a metal pipe with a diameter smaller than a set value; the risk assessment method includes the following contents: Calculate the failure probability factor k based on the internal and external environmental corrosion, material and vibration conditions of the small metal nozzle; According to the toxicity and flammability of the medium contained in the small metal pipe, the operating temperature and operating pressure of the small metal pipe, and combined with the consequence correction coefficient, calculate the failure consequence factor h; Calculate the risk value R using the failure possibility factor k and the failure consequence factor h; Introduce the test correction coefficient β to test and correct the risk value R, and obtain the risk value R after test correction new ; The value of the inspection correction coefficient β is related to the inspection validity, the number of inspections and whether defects are detected; According to the risk value R after test correction new Evaluate the risk of small metal nozzles.

2. A risk assessment method for small metal pipes based on inspection correction coefficient according to claim 1, characterized in that: The specific method of determining the value of the inspection correction coefficient β is as follows: If the inspection is not performed or is invalid, the inspection correction factor is β1; If the first inspection is conducted and no defects are detected, the inspection correction factor is β2; If two or more inspections are conducted and no defects are found, the inspection correction factor is β3; If defects are found during inspection and the small metal pipe has been repaired, the inspection correction factor is β4; Among them, β4>β1≥1>β2>β3; If defects are detected and the small metal nozzle is not repaired, the risk of the small metal nozzle will be directly considered to be the greatest.

3. The risk assessment method for small metal pipes based on inspection correction coefficient according to claim 1 is characterized in that: The calculation method of failure probability factor k is: ； In the formula, t1, t2, and t3 are the corrosion score, material score, and vibration score of the small metal pipe respectively; k1, k2, and k3 are the weight coefficients of t1, t2, and t3 respectively, and k1+k2+k3=1; ∏ is the sign of the continuous product; Among them, the stronger the internal and external environmental corrosion of the small metal nozzle, the higher the corrosion score t1; the less the material of the small metal nozzle meets the process requirements, the higher the material score t2; the greater the vibration of the small metal nozzle, the higher the vibration score t3; the greater the value of the failure possibility factor k, the greater the possibility of failure.

4. The risk assessment method for small metal pipes based on inspection correction coefficient according to claim 3 is characterized in that: The internal and external environmental corrosion levels of small metal pipes are divided into strong corrosion, certain corrosion, slight corrosion, and non-corrosive, and the corresponding corrosion scores t1 are t11, t12, t13, and t14 respectively; among which, t11>t12>t13>t14>1; The classification method of the internal and external environmental corrosivity level is as follows: if the annual corrosion rate a ≥ α1 or the damage sensitivity is high, it is judged as strong corrosiveness; if the annual corrosion rate a∈[α2,α1) or the damage sensitivity is medium, it is judged as certain corrosiveness; if the annual corrosion rate a∈[α3,α2) or the damage sensitivity is low, it is judged as slight corrosiveness; if the annual corrosion rate a<α3 or the damage sensitivity is zero, it is judged as slight corrosiveness; among which, α1>α2>α3; The calculation method of annual corrosion rate a is: assuming that the minimum wall thickness of the metal small pipe in this test is s, the minimum wall thickness in the last test is s0, and the time difference between this test and the last test is n, a=(s-s0) / n; where the unit of annual corrosion rate is mm / year, the unit of wall thickness is mm, and the unit of time difference is year; The damage sensitivity is divided into four levels: high, medium, low, and none. First, determine whether the internal and external environment of the small metal nozzle has damage mechanisms such as environmental cracking, material degradation, mechanical damage, corrosion thinning or other damage, and determine the damage mechanism category of the small metal nozzle; then, based on the inspection results, determine the damage sensitivity corresponding to different damage mechanism categories.

5. The risk assessment method for small metal pipes based on inspection correction coefficient according to claim 3 is characterized in that: The material grade of the small metal pipe is divided into those that do not meet the process requirements and those that meet the process requirements, and the corresponding material scores t2 are t21 and t22 respectively; among which t21>t22>1; The material grades are divided as follows: if the material of the small metal pipe is inconsistent with the main material of the container or pipeline, or the material of the small metal pipe does not meet the material selection requirements, it is judged as not meeting the process requirements; if the material of the small metal pipe is consistent with the main material of the container or pipeline, and the material of the small metal pipe meets the material selection requirements, it is judged as meeting the process requirements.

6. The risk assessment method for small metal pipes based on inspection correction coefficient according to claim 3 is characterized in that: The vibration level of the small metal pipe is divided into strong vibration, weak vibration and no vibration according to the vibration frequency, and the corresponding vibration scores t3 are t31, t32 and t33 respectively; among which, t31>t32>t33>1.

7. The risk assessment method for small metal nozzles based on inspection correction coefficient according to claim 1 is characterized in that: The calculation method of failure consequence factor h is: ； Wherein, C0 represents the consequence correction coefficient; h1, h2, h3, and h4 represent the toxicity score, flammability score, operating temperature score, and operating pressure score of the small metal pipe respectively; Among them, the higher the toxicity hazard of the medium contained in the small metal pipe, the greater the toxicity score h1; the higher the flammability level of the medium contained in the small metal pipe, the greater the flammability score h2; the higher the operating temperature of the small metal pipe, the greater the operating temperature score h3; the higher the operating pressure of the small metal pipe, the greater the operating pressure score h4; the greater the value of the failure consequence factor h, the more serious the failure consequence.

8. The risk assessment method for small metal pipes based on inspection correction coefficient according to claim 7 is characterized in that: If the medium contained in the small metal pipe is an explosive medium, and the operating temperature of the small metal pipe exceeds the set temperature or the operating pressure exceeds the set pressure, then C0 takes the value of δ1; if the toxicity score h1 of the small metal pipe exceeds the set value, then C0 takes the value of δ2; otherwise, C0 takes the value of δ3; where δ1>δ2>δ3≥1.

9. A risk assessment method for small metal nozzles based on inspection correction coefficient according to any one of claims 1 to 8, characterized in that: Risk value R = k·h; test the corrected risk value R new =β·R; R new The larger it is, the greater the risk of small metal takeovers.

10. A computer program product, characterized in that It includes a computer program / instruction, which, when executed by a processor, implements a risk assessment method for a small metal nozzle based on an inspection correction coefficient as described in any one of claims 1 to 9.

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