Method for preventing water and ice in the pressure guide pipe of an air compressor flowmeter

Abstract

The application discloses a method for preventing water and ice in a guide pressure pipe of an air compressor flowmeter, and is directed to a flow transmitter part in an air compressor control system. The method is characterized in that the flow monitoring and control of the set flow transmitter are established through the control logic based on the DCS setting, and the water in the guide pressure pipe is timely treated according to the flow monitoring and control. The method for preventing water and ice in the guide pressure pipe of the air compressor flowmeter is characterized in that the sampling device of the air compressor flow transmitter is reformed, the differential pressure switch for detecting the water level of the water storage tank is added, the electromagnetic valve is additionally arranged, and the logic control program is added, so that the water in the water storage tank is automatically discharged, the air compressor is prevented from being tripped and stopped due to the flow detection error caused by the water in the guide pressure pipe of the air compressor flow transmitter, and the stable operation of the air compressor equipment is ensured.

Description

Technical Field

[0001] This invention belongs to the field of air compressor flow detection, specifically relating to a method for preventing water from entering and freezing inside the pressure guide pipe of an air compressor flow meter. Background Technology

[0002] In industrial production, an air compressor is a device that draws in air, compresses and pressurizes it, and then delivers it through pipelines to subsequent processes, thus providing air as a raw material for those processes. Figure 1 The diagram shown is a schematic of the air compressor control system.

[0003] The air filter at the front end of the air compressor removes dust, mechanical particles, and other impurities from the atmosphere. The electric motor drives the compressor impeller to rotate, drawing air into the compressor and compressing it. The air pressure is increased from 1 atmosphere (0.1 MPa / 100 kPa) to a specified value of 0.6 MPa, and then transported to the next process through the outlet pipe. A flow orifice plate designed for this operating condition is installed on the air compressor outlet pipe. After the compressed air flows through the orifice plate, a differential pressure is generated before and after the orifice plate. This differential pressure corresponds to the flow rate, and the corresponding flow rate can be calculated by detecting this differential pressure using a differential pressure transmitter.

[0004] Q = k*SQRT(△P), where the flow rate is linearly related to the square root of the differential pressure across the orifice.

[0005] When measuring gas flow rate, temperature and pressure compensation is necessary because the density of a gas varies under different temperatures and pressures. The flow rate compensation formula is as follows:

[0006] Q' = Q * SQRT(Tset / (273+Tactual)*(Pactual+101) / Pset)

[0007] Parameters in the formula:

[0008] Q': Actual traffic

[0009] Q: Flow rate before compensation

[0010] T is set as follows: Design temperature (K)

[0011] Tactual: Actual temperature (°C)

[0012] Pactual: Actual pressure (kPa)

[0013] P assumes: Design pressure (KPa)

[0014] As can be seen from the formula, the final flow rate is determined by the orifice differential pressure, fluid pressure, and fluid temperature.

[0015] This flow rate value is not only a monitoring value for increasing or decreasing the flow rate of the air compressor, but also a control variable for the air compressor's anti-surge control automatic adjustment system. When the flow rate is low and the compressor is about to enter the surge zone, the DCS will alarm and gradually open the vent valve. If the flow rate continues to drop to the protection interlock value, the air compressor will trip and stop production. Therefore, this flow rate is a crucial parameter for the operation of the air compressor, and its accuracy must be ensured.

[0016] Because the atmosphere contains water vapor, and water vapor is also present in compressed air, the two instrument pressure guides used to transmit air pressure from both sides of the orifice plate to the positive and negative pressure sides of the differential pressure transmitter also contain water vapor. The water vapor in the air within these guides condenses into liquid droplets due to ambient temperature, accumulating at the bottom of the guides under gravity and gradually rising. Ultimately, the pressures transmitted to the positive and negative pressure chambers of the differential pressure transmitter for flow detection are the pressures before and after the orifice plate plus the pressure corresponding to the height of the condensate column in the guides. However, the amount of condensate in the two guides is not exactly the same, causing the differential pressure measured by the transmitter to not represent the actual pressure difference before and after the orifice plate. Therefore, the flow rate measured by the differential pressure transmitter is not the true flow rate. When water entering the differential pressure transmitter's diaphragm freezes, it can damage the diaphragm, causing permanent deformation of the elastic element, loss of elasticity, and damage to the equipment.

[0017] like Figure 2 As shown, the manual sampling valves V1 and V2 originate from the inlet and outlet sides of the flow orifice plate, respectively, and enter the positive and negative pressure chambers of the differential pressure transmitter FT-101 through the positive and negative pressure guide pipes. At the same time, the sampling gas from the positive pressure guide pipe enters the pressure transmitter PT101. Water storage tanks C1 and C2 are installed at the bottom of the positive and negative pressure guide pipes of the differential pressure transmitter, respectively. Manual valves V3, V4, V5, and V6 are installed at the inlet and outlet of C1 and C2, respectively, for draining the water storage tanks.

[0018] Typically, electric heating tape is used to heat the positive and negative pressure guide pipes, water storage tank, and valve bodies V1-V6. The electric heating tape and all the above components are then completely covered with insulation material to prevent heat loss. For ease of operation, only the valve operating handles of V1-V6 are exposed. The area within the dotted line represents the electric heating tape and insulation material.

[0019] Water in the pressure-conducting pipe directly affects flow rate detection. The water storage tank is for collecting and storing condensate from the pressure-conducting pipe. When the tank is full, the water level continues to rise. Once the water level exceeds the installation height of the differential pressure transmitter, the flow rate reading becomes inaccurate. According to the design of the orifice plate, at maximum flow, the differential pressure across the orifice plate is typically only a few kPa. Taking the air compressor of the No. 1 oxygen generator in Baosteel's Energy and Environmental Department as an example, at the maximum design flow rate of 200,000 Nm³ / h (standard cubic meters per hour), the differential pressure across the orifice plate is 8 kPa, or 800 mmH₂O. Under normal operating conditions of 150,000 Nm³ / h, the differential pressure is approximately 4.8 kPa, or 480 mmH₂O. Therefore, the pressure generated by the liquid column after water enters the pressure-conducting pipe has a significant impact on the detection results.

[0020] Existing problems:

[0021] (1) Water has a freezing point of about 0°C and a boiling point of 150°C under a pressure of 600 kPa (0.6 MPa), meaning it exists in a liquid state between 0°C and 150°C. Therefore, the heating cable with the outer shell insulation material cannot prevent the formation of condensation, but can only slow down the formation of water accumulation.

[0022] (2) Due to seasonal and temperature differences, the atmospheric moisture content varies, resulting in different moisture content in the compressed air and different rates of condensation. In addition, leaks in the air compressor's cooler equipment can also cause the compressed air to contain moisture. Therefore, it is impossible to determine the cycle for manually draining the water from the storage tank.

[0023] (3) It is necessary to manually drain the water in the water tank at the bottom of the pressure guide pipe. Because there are many valves to operate, and they need to be operated in a certain order, if the order of operation is not correct, it will directly cause the flow detection data to be wrong, causing the air compressor to shut down and the risk is high.

[0024] (4) When encountering extremely cold weather such as cold waves, a large amount of water will condense in the water storage tank and pressure-conducting pipe in a relatively short period of time. When the cold wave lasts for several days, the efficiency of the electric heating tape decreases, and the insulation material cannot completely isolate heat exchange from the outside. The water in the pressure-conducting pipe and water storage tank will freeze again if it is not drained for a long time. Since it is impossible to determine the amount of condensate in the water storage tank, the need for manual drainage of water is relatively frequent in order to ensure that the air in the pressure-conducting pipe is dry. On-site drainage cannot be guaranteed at any time, and the risk of accidental shutdown is also increased.

[0025] Application CN201010107609.0 discloses an "anti-condensation device for an instrument pressure guide pipe," which includes a pressure guide pipe with its two ends connected to a pressure transmitter and the device under test, respectively. The key feature is that the pressure guide pipe is equipped with an isolation device that separates the pressure guide pipe and the device under test into two non-communicating parts, and allows pressure to be transmitted within these two parts. By providing a pressure-transmitting isolation device on the pressure guide pipe, the pressure guide pipe and the device under test are isolated. This prevents liquid from the device under test from flowing into the pressure guide pipe and contaminating the clean flushing oil inside. Therefore, the flushing oil in the pressure guide pipe will not freeze, and the pressure guide pipe no longer requires steam tracing.

[0026] Invention application CN201811640917.2 discloses "a flow meter and its pressure guiding pipeline device," comprising: a positive pressure pipe, one end of which is provided with a positive pressure pipe connector, and the other end of which is provided with a transmitter positive pressure connector; a negative pressure pipe, one end of which is provided with a negative pressure pipe connector, and the other end of which is provided with a transmitter negative pressure connector; a positive pressure valve disposed in the positive pressure pipe; and a negative pressure valve disposed in the negative pressure pipe. By using a pressure guiding pipeline device to replace the three-way valve assembly and five-way valve assembly in the prior art, the inner diameter of the pressure guiding pipeline in this invention can be set sufficiently large. Furthermore, the positive pressure valve and negative pressure valve with sufficiently large inner diameters can be selected for the internal pipelines.

[0027] The invention application with application number CN201911367311.0 discloses "a method for online unblocking and anti-clogging of pressure-conducting pipes". This method involves adding three two-position three-way solenoid valves, two manual discharge valves, and corresponding connecting pipes to the pressure-conducting pipes of the pressure transmitter and pressure gauge on the existing cooling water main pipeline. By switching and operating the relevant valves, while ensuring continuous online monitoring of the pressure value data of the cooling water main pipeline by the pressure transmitter, the pressure-conducting pipes of the pressure transmitter and pressure gauge can be cleaned and unblocked online at any time without shutting down the system. This reliably prevents blockage of the pressure-conducting pipes and avoids false alarms and accidental shutdowns of equipment operating parameters.

[0028] The invention application with application number CN202122087583.4 discloses "a liquid settling device for a pressure-conducting pipeline". Liquid accumulated at the bottom of the well and in the wellbore is carried out or lifted out of the gas well along with the gas flow and flows along the pressure-conducting pipeline. The settling device is located at the lower end of the pressure-conducting pipeline, and the input end of the settling device is connected to the pressure-conducting pipeline. Utilizing the large density difference between liquid and natural gas, under the action of gravity, the liquid enters the settling device along the pressure-conducting pipeline, achieving effective separation of liquid and natural gas. The output end of the settling device is equipped with an on / off valve. By opening the on / off valve at the output end of the settling device, the liquid is discharged, thereby achieving the purpose of clearing the liquid accumulated in the pressure-conducting pipeline. This solves the problem of inaccurate measurement and flowmeter malfunction caused by liquid entering the differential pressure flowmeter along the pressure-conducting pipeline with the gas flow. Summary of the Invention

[0029] To address the above problems, this invention provides a method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter, the specific technical solution of which is as follows:

[0030] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter, specifically targeting the flow transmitter section of the air compressor control system, is characterized by:

[0031] By establishing control logic based on DCS settings, flow monitoring and control of the set flow transmitter are achieved, thereby enabling timely treatment of water stored in the pressure-conducting pipe.

[0032] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to the present invention is characterized in that:

[0033] Flow monitoring and control are carried out in a manner that adapts to changes in operating conditions.

[0034] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to the present invention is characterized in that:

[0035] The flow transmitters configured include:

[0036] Pressure guiding pipes are installed on both sides of the flow orifice plate in the outlet pipe of the air compressor;

[0037] The pressure guiding pipe includes a positive pressure guiding pipe disposed on the inlet side of the flow orifice plate and a negative pressure guiding pipe disposed on the outlet side of the flow orifice plate;

[0038] A first manual valve (V1), a pressure transmitter (PT101), a third manual valve (V3), a first solenoid valve (SV1), a first water storage tank (C1), and a third solenoid valve (SV3) are sequentially installed on the positive pressure side pressure guiding pipe.

[0039] A second manual valve (V2), a fourth manual valve (V4), a second solenoid valve (SV2), a second water storage tank (C2), and a fourth solenoid valve (SV4) are sequentially installed on the negative pressure side pressure guiding pipe.

[0040] A differential pressure transmitter (FT101) is installed on the pipe section between the positive pressure side guide pipe and the negative pressure side guide pipe, between the first manual valve (V1) and the third manual valve (V3), and on the pipe section between the corresponding second manual valve (V2) and the second solenoid valve (SV2).

[0041] A first differential pressure switch (PDS1) is installed on the pipe section between the first solenoid valve (SV1) and the first water tank (C1) before the bottom of the first water tank (C1); a second differential pressure switch (PDS2) is installed on the pipe section between the second solenoid valve (SV2) and the second water tank (C2) before the bottom of the second water tank (C2).

[0042] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to the present invention is characterized in that:

[0043] The operating conditions include: normal drainage conditions and maintenance conditions;

[0044] Normal drainage conditions and maintenance conditions are mutually exclusive operating states.

[0045] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to the present invention is characterized in that:

[0046] The flow transmitters configured include:

[0047] Pressure guiding pipes are installed on both sides of the flow orifice plate in the outlet pipe of the air compressor;

[0048] The pressure guiding pipe includes a positive pressure guiding pipe disposed on the inlet side of the flow orifice plate and a negative pressure guiding pipe disposed on the outlet side of the flow orifice plate;

[0049] A first manual valve (V1), a pressure transmitter (PT101), a third manual valve (V3), a first solenoid valve (SV1), a first water storage tank (C1), and a third solenoid valve (SV3) are sequentially installed on the positive pressure side pressure guiding pipe.

[0050] A second manual valve (V2), a fourth manual valve (V4), a second solenoid valve (SV2), a second water storage tank (C2), and a fourth solenoid valve (SV4) are sequentially installed on the negative pressure side pressure guiding pipe.

[0051] A differential pressure transmitter (FT101) is installed on the pipe section between the positive pressure side guide pipe and the negative pressure side guide pipe, between the first manual valve (V1) and the third manual valve (V3), and on the pipe section between the corresponding second manual valve (V2) and the second solenoid valve (SV2).

[0052] A first differential pressure switch (PDS1) is installed on the pipe section between the first solenoid valve (SV1) and the first water tank (C1) before the bottom of the first water tank (C1); a second differential pressure switch (PDS2) is installed on the pipe section between the second solenoid valve (SV2) and the second water tank (C2) before the bottom of the second water tank (C2).

[0053] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to the present invention is characterized in that:

[0054] The operating conditions include: normal drainage conditions and maintenance conditions;

[0055] Normal drainage conditions and maintenance conditions are mutually exclusive operating states.

[0056] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to the present invention is characterized in that:

[0057] The operating conditions also include: switching the flow transmitter on / off operating condition, alarm and alarm post-processing operating condition.

[0058] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to the present invention is characterized in that:

[0059] The operating conditions also include: switching the flow transmitter on / off operating condition, alarm and alarm post-processing operating condition.

[0060] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to the present invention is characterized in that:

[0061] The specific steps for monitoring and controlling flow based on normal drainage conditions are as follows:

[0062] S1: Open the first manual valve (V1), the second manual valve (V2), the third manual valve (V3), the fourth manual valve (V4), the first solenoid valve (SV1), and the second solenoid valve (SV2); close the third solenoid valve (SV3) and the fourth solenoid valve (SV4); when either the first water tank (C1) or the second water tank (C2) is detected to be full, the corresponding differential pressure switch sends a water tank full signal to the DCS;

[0063] S2: After receiving the full water signal, the DCS issues a drainage command. According to the drainage command, the first solenoid valve (SV1) and the second solenoid valve (SV2) are triggered to close, and the third solenoid valve (SV3) and the fourth solenoid valve (SV4) are triggered to open.

[0064] S3: After the DCS issues a drainage command within a set time, the DCS issues a purging command, which triggers the opening of the first solenoid valve (SV1) and the second solenoid valve (SV2).

[0065] S4: After a set time following the issuance of the purging command by the DCS, the DCS outputs a command indicating the completion of one drainage process. Based on the command, the third solenoid valve (SV3) and the fourth solenoid valve (SV4) are triggered to close, and the flow monitoring and control of the next cycle begins.

[0066] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to the present invention is characterized in that:

[0067] The specific steps for monitoring and controlling flow based on maintenance conditions are as follows:

[0068] SS1: After receiving the maintenance signal, the DCS issues a standby command. According to the standby command, the first manual valve (V1), the second manual valve (V2), the third manual valve (V3), the fourth manual valve (V4), the third solenoid valve (SV3), and the fourth solenoid valve (SV4) are closed, while the first solenoid valve (SV1) and the second solenoid valve (SV2) remain open.

[0069] SS2: After maintenance is completed, the DCS receives the purging signal and issues a forced drainage command accordingly. According to the forced drainage command, the first manual valve (V1), the second manual valve (V2), the third manual valve (V3), the fourth manual valve (V4), the third solenoid valve (SV3), and the fourth solenoid valve (SV4) are opened, and the first solenoid valve (SV1) and the second solenoid valve (SV2) are kept open. After a set time, the third solenoid valve (SV3) and the fourth solenoid valve (SV4) are closed to complete the maintenance operation.

[0070] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to the present invention is characterized in that:

[0071] The flow monitoring and control system, based on alarm and post-alarm processing conditions, follows these steps:

[0072] SA1: The set time before the DCS issues the drain command locks the flow value FI101 of the flow indicator after temperature and pressure compensation calculation in the air compressor control system, so that the flow indicator regulator FIC101 controls the vent valve signal to remain stable.

[0073] SA2: Send the real-time flow value after temperature and pressure compensation calculation to register M1, and compare the real-time value sent to M1 with the locked flow value FI101 in real time to obtain a set of differences △F in the time series;

[0074] SA3: Compare the absolute value of each ΔF with 2% of the locked flow value FI101. If the absolute value is less than 2% of the locked flow value FI101, the lock on the flow indicator value is released and normal monitoring is performed; otherwise, an alarm is triggered.

[0075] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to the present invention is characterized in that:

[0076] The real-time value sent to register M1 in step SA2 starts from the moment the flow rate value FI101 of the flow indicator is locked and continues until the drainage is completed.

[0077] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to the present invention is characterized in that:

[0078] The "set time before the DCS issues the drainage command" mentioned in step SA1 is specifically 2 seconds before the DCS issues the drainage command.

[0079] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to the present invention is characterized in that:

[0080] The "monitoring and control of flow rate entering the next cycle" in step S4 is performed 2 seconds after the third solenoid valve (SV3) and the fourth solenoid valve (SV4) are closed.

[0081] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to the present invention is characterized in that:

[0082] In step S3, the set time in "DCS issues a purging command after the set time of the DCS issuing a drainage command" is set by adding 4-6 seconds to the theoretical emptying time of the water storage tank.

[0083] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to the present invention is characterized in that:

[0084] Normal drainage operation is based on automatic mode;

[0085] Maintenance operations are performed in manual mode.

[0086] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to the present invention is characterized in that:

[0087] The first solenoid valve (SV1), the second solenoid valve (SV2), the third solenoid valve (SV3), and the fourth solenoid valve (SV4) are all remotely wirelessly controlled for on / off switching.

[0088] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to the present invention is characterized in that:

[0089] In step SS1, the DCS receives manually issued maintenance signals based on the configured human-machine interface.

[0090] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to the present invention is characterized in that:

[0091] The "unlocking of the flow indicator flow value" mentioned in step SA3 is achieved manually through the set human-computer interaction interface.

[0092] This invention provides a method for preventing water accumulation and freezing in the pressure-conducting pipe of an air compressor flow meter. A differential pressure switch is used to detect the pressure difference between the top and bottom of the water storage tank in the pressure-conducting pipe, determining the water level in the tank. A newly added logic program on the DCS terminal controls the opening and closing of the solenoid valves at the inlet and outlet of the added water storage tank, achieving an automatic drainage function. Before the condensate water level in the water storage tank of the air compressor flow meter pressure-conducting pipe affects the normal flow detection, the condensate water in the tank is automatically drained, preventing water accumulation and freezing in the pressure-conducting pipe that could affect the accuracy of air compressor flow detection. Simultaneously, this control logic program keeps the flow value stable during the automatic drainage process, preventing drastic fluctuations in the flow value and thus avoiding air compressor shutdown. Furthermore, it integrates various operating conditions and sets the control logic holistically.

[0093] In summary, the present invention provides a method for preventing water and ice formation in the pressure-conducting pipe of an air compressor flow meter. By modifying the sampling device of the air compressor flow transmitter, adding a differential pressure switch to detect the water level in the storage tank, adding a solenoid valve, and adding a logic control program, the method achieves automatic discharge when the storage tank is full. This eliminates the air compressor's accidental tripping and production stoppage caused by flow detection errors due to water in the pressure-conducting pipe of the air compressor flow transmitter, ensuring the stable operation of the air compressor equipment. Attached Figure Description

[0094] Figure 1 This is a schematic diagram of the structure of a conventional air compressor control system in the background art of this invention;

[0095] Figure 2 This is a schematic diagram of the sampling principle of the original flow transmitter in the background art of this invention;

[0096] Figure 3 This is a schematic diagram of the sampling principle of the flow transmitter of the present invention;

[0097] Figure 4 for Figure 3 Detailed schematic diagram of the differential pressure switch for water level detection;

[0098] Figure 5 This is a schematic diagram of the control logic in an embodiment of the present invention;

[0099] Figure 6 This is a schematic diagram of the flow monitoring and control sequence based on normal drainage conditions in this invention.

[0100] Figure 7 This is a schematic diagram of the flow monitoring and control sequence based on maintenance conditions in this invention.

[0101] Figure 8 This is a schematic diagram of the flow monitoring and control sequence based on maintenance conditions in this invention.

[0102] Figure 1 middle,

[0103] FI - Flow Indicator;

[0104] FIC - Flow Indicator Regulator;

[0105] Figure 2 middle,

[0106] V1, V2, V3, V4, V5, and V6 are all manual valves;

[0107] PT - Pressure Transmitter;

[0108] FT-Differential Pressure Transmitter;

[0109] C1 and C2 are both water storage tanks;

[0110] Figure 3 , 4 middle,

[0111] V1 - First manual valve;

[0112] V2 - Second manual valve;

[0113] V3 - Third manual valve;

[0114] V4 - Fourth manual valve;

[0115] SV1 - First solenoid valve;

[0116] SV2 - Second solenoid valve;

[0117] SV3 - Third solenoid valve;

[0118] SV4 - Fourth solenoid valve;

[0119] PT101 - Pressure Transmitter;

[0120] FT101 - Differential Pressure Transmitter;

[0121] C1 - First water storage tank;

[0122] C2 - Second water storage tank;

[0123] PDS1 - First differential pressure switch;

[0124] PDS2 - Second differential pressure switch. Detailed Implementation

[0125] The following is a detailed description of a method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter, based on the accompanying drawings and specific embodiments.

[0126] A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter is proposed. This method targets the flow transmitter in the air compressor control system. By establishing control logic based on DCS settings, the flow of the flow transmitter is monitored and controlled, thereby enabling timely treatment of water stored in the pressure-conducting pipe.

[0127] in,

[0128] Flow monitoring and control are carried out in a manner that adapts to changes in operating conditions.

[0129] in,

[0130] The flow transmitters configured include:

[0131] Pressure guiding pipes are installed on both sides of the flow orifice plate in the outlet pipe of the air compressor;

[0132] The pressure guiding pipe includes a positive pressure guiding pipe disposed on the inlet side of the flow orifice plate and a negative pressure guiding pipe disposed on the outlet side of the flow orifice plate;

[0133] A first manual valve (V1), a pressure transmitter (PT101), a third manual valve (V3), a first solenoid valve (SV1), a first water storage tank (C1), and a third solenoid valve (SV3) are sequentially installed on the positive pressure side pressure guiding pipe.

[0134] A second manual valve (V2), a fourth manual valve (V4), a second solenoid valve (SV2), a second water storage tank (C2), and a fourth solenoid valve (SV4) are sequentially installed on the negative pressure side pressure guiding pipe.

[0135] A differential pressure transmitter (FT101) is installed on the pipe section between the positive pressure side guide pipe and the negative pressure side guide pipe, between the first manual valve (V1) and the third manual valve (V3), and on the pipe section between the corresponding second manual valve (V2) and the second solenoid valve (SV2).

[0136] A first differential pressure switch (PDS1) is installed on the pipe section between the first solenoid valve (SV1) and the first water tank (C1) before the bottom of the first water tank (C1); a second differential pressure switch (PDS2) is installed on the pipe section between the second solenoid valve (SV2) and the second water tank (C2) before the bottom of the second water tank (C2).

[0137] in,

[0138] The operating conditions include: normal drainage conditions and maintenance conditions;

[0139] Normal drainage conditions and maintenance conditions are mutually exclusive operating states.

[0140] in,

[0141] The operating conditions also include: switching the flow transmitter on / off operating condition, alarm and alarm post-processing operating condition.

[0142] in,

[0143] The specific steps for monitoring and controlling flow based on normal drainage conditions are as follows:

[0144] S1: Open the first manual valve (V1), the second manual valve (V2), the third manual valve (V3), the fourth manual valve (V4), the first solenoid valve (SV1), and the second solenoid valve (SV2); close the third solenoid valve (SV3) and the fourth solenoid valve (SV4); when either the first water tank (C1) or the second water tank (C2) is detected to be full, the corresponding differential pressure switch sends a water tank full signal to the DCS;

[0145] S2: After receiving the full water signal, the DCS issues a drainage command. According to the drainage command, the first solenoid valve (SV1) and the second solenoid valve (SV2) are triggered to close, and the third solenoid valve (SV3) and the fourth solenoid valve (SV4) are triggered to open.

[0146] S3: After the DCS issues a drainage command within a set time, the DCS issues a purging command, which triggers the opening of the first solenoid valve (SV1) and the second solenoid valve (SV2).

[0147] S4: After a set time following the issuance of the purging command by the DCS, the DCS outputs a command indicating the completion of one drainage process. Based on the command, the third solenoid valve (SV3) and the fourth solenoid valve (SV4) are triggered to close, and the flow monitoring and control of the next cycle begins.

[0148] in,

[0149] The specific steps for monitoring and controlling flow based on maintenance conditions are as follows:

[0150] SS1: After receiving the maintenance signal, the DCS issues a standby command. According to the standby command, the first manual valve (V1), the second manual valve (V2), the third manual valve (V3), the fourth manual valve (V4), the third solenoid valve (SV3), and the fourth solenoid valve (SV4) are closed, while the first solenoid valve (SV1) and the second solenoid valve (SV2) remain open.

[0151] SS2: After maintenance is completed, the DCS receives the purging signal and issues a forced drainage command accordingly. According to the forced drainage command, the first manual valve (V1), the second manual valve (V2), the third manual valve (V3), the fourth manual valve (V4), the third solenoid valve (SV3), and the fourth solenoid valve (SV4) are opened, and the first solenoid valve (SV1) and the second solenoid valve (SV2) are kept open. After a set time, the third solenoid valve (SV3) and the fourth solenoid valve (SV4) are closed to complete the maintenance operation.

[0152] in,

[0153] The flow monitoring and control system, based on alarm and post-alarm processing conditions, follows these steps:

[0154] SA1: The set time before the DCS issues the drain command locks the flow value FI101 of the flow indicator after temperature and pressure compensation calculation in the air compressor control system, so that the flow indicator regulator FIC101 controls the vent valve signal to remain stable.

[0155] SA2: Send the real-time flow value after temperature and pressure compensation calculation to register M1, and compare the real-time value sent to M1 with the locked flow value FI101 in real time to obtain a set of differences △F in the time series;

[0156] SA3: Compare the absolute value of each ΔF with 2% of the locked flow value FI101. If the absolute value is less than 2% of the locked flow value FI101, the lock on the flow indicator value is released and normal monitoring is performed; otherwise, an alarm is triggered.

[0157] in,

[0158] The real-time value sent to register M1 in step SA2 starts from the moment the flow rate value FI101 of the flow indicator is locked and continues until the drainage is completed.

[0159] in,

[0160] The "set time before the DCS issues the drainage command" mentioned in step SA1 is specifically 2 seconds before the DCS issues the drainage command.

[0161] in,

[0162] The "monitoring and control of flow rate entering the next cycle" in step S4 is performed 2 seconds after the third solenoid valve (SV3) and the fourth solenoid valve (SV4) are closed.

[0163] in,

[0164] In step S3, the set time in "DCS issues a purging command after the set time of the DCS issuing a drainage command" is set by adding 4-6 seconds to the theoretical emptying time of the water storage tank.

[0165] in,

[0166] Normal drainage operation is based on automatic mode;

[0167] Maintenance operations are performed in manual mode.

[0168] in,

[0169] The first solenoid valve (SV1), the second solenoid valve (SV2), the third solenoid valve (SV3), and the fourth solenoid valve (SV4) are all remotely wirelessly controlled for on / off switching.

[0170] in,

[0171] In step SS1, the DCS receives manually issued maintenance signals based on the configured human-machine interface.

[0172] in,

[0173] The "unlocking of the flow indicator flow value" mentioned in step SA3 is achieved manually through the set human-computer interaction interface.

[0174] Working principle, process and implementation examples

[0175] The following explanation combines Figure 1 See also Figure 3-8 conduct.

[0176] 1. Detecting a full water tank using the principle of gravity.

[0177] Taking the No. 1 air compressor in the Energy and Environmental Protection Department of Baosteel Co., Ltd. as an example, the internal radius of the pressure-conducting pipe water tank of the flow transmitter is about 50mm, and the internal height is 200mm. The pressure-conducting pipe with an outer diameter of 8mm has an internal radius of 3mm, and the top of the water tank is about 5 meters away from the differential pressure transmitter.

[0178] Water storage tank volume: 3.14 * 50 * 50 * 200 = 1,570,000 cubic millimeters, approximately 1.5 liters. Pressure guide pipe volume: 3.14 * 3 * 3 * 5000 = 141,300 cubic millimeters, approximately 0.14 liters. It is evident that the water storage tank volume is more than 10 times that of the pressure guide pipe. Therefore, draining the water from the pressure guide pipe before it becomes full after the storage tank is full ensures the maximum effectiveness of the storage tank and allows for sufficient lead time before water accumulation affects the differential pressure transmitter's detection, thus guaranteeing safe and stable flow measurement.

[0179] According to the principle of pressure action:

[0180] P'=P+ρgh,

[0181] ρ is the density of water, g is the acceleration due to gravity, h is the height of the water column in the storage tank; P' is the bottom pressure, and P is the top pressure.

[0182] Differential pressure switches are installed next to the water storage tanks on the positive and negative pressure guide pipes, respectively. The pressure at the bottom of the tank is introduced into the positive pressure side of the differential pressure switch, and the pressure at the top of the tank is introduced into the negative pressure side of the differential pressure switch. The operating value of the differential pressure switch is set to the pressure generated by the liquid column height when the water storage tank is full, i.e., the pressure generated by 200 mmH2O.

[0183] ρgh=1*9.8*200=1960pa=1.96kpa

[0184] When the differential pressure between the bottom and top of the water tank exceeds a certain value, the differential pressure switch activates. Activation of the differential pressure switch indicates that the water tank is full. If either the positive or negative pressure side of the water tank is full, it means that condensate will soon affect the flow rate detection. In this case, all water in both water tanks should be drained. (See...) Figure 4 )

[0185] 2. Modification of pressure-conducting pipe and water storage tank pipeline

[0186] To achieve automatic discharge, the pressure-conducting water tank pipeline was modified. The manual valves V3 and V4, which are operated manually on site, were retained for isolation during maintenance. Solenoid valves SV1 and SV2, which can be controlled by remote electrical signals, were installed below V3 and V4, respectively. The manual valves V5 and V6 were removed and replaced with solenoid valves SV3 and SV4, which can be controlled by remote electrical signals, respectively. All four solenoid valves are 2-position 2-way solenoid valves, and the switching action time is approximately ≤0.5 seconds. When the solenoid valve coil is energized, the valve core immediately opens, and the fluid medium flows from the inlet to the outlet. When the solenoid valve coil is de-energized, the valve core immediately closes, cutting off the flow of the fluid medium.

[0187] During normal testing, V1 to V4 are all in the open state. When any water tank C1 or C2 is full, and the differential pressure between the upper and lower ends of the water tank reaches the differential pressure action value of 1.96 kPa of the differential pressure switch PDS1 or PDS2, the differential pressure switch action signal is input to the DCS. The control logic program then switches the solenoid valves on and off according to the prescribed sequence to drain and purge the water tanks. After the drainage process is completed, the solenoid valves automatically return to the normal testing state.

[0188] 3. DCS control logic program

[0189] Drainage requires the coordinated operation of on-site drainage solenoid valves and control logic. By writing a logic control program on the DCS, the four solenoid valves are automatically opened and closed based on signals from the differential pressure switch, thus achieving automatic drainage, as well as manually selected forced drainage as needed. (See...) Figure 5 )

[0190] The operator selects the operation mode for draining the water storage tank on the DCS control station, offering two options: Automatic (AUTO) or Manual (MAN). In Automatic mode, drainage will begin when either the differential pressure switch PDS1 or PDS2 for water level detection in the storage tank is activated. This is the commonly used mode during normal operation of the air compressor. Otherwise, the DCS will display a flashing "Non-AUTO" message. In Manual mode, the operator enters the next level of the mode selection interface, offering Forced Drainage or Standby mode. Forced Drainage will initiate drainage directly, regardless of whether the storage tank is full. This mode is used for purging and draining the pipelines upon initial startup after air compressor maintenance. Standby mode will not initiate drainage and is used for transmitter maintenance.

[0191] Upon entering the drainage start-up state, the solenoid valves SV1 and SV2 at the top of the two water tanks are first triggered to close, while the solenoid valves SV3 and SV4 at the bottom of the two water tanks are simultaneously energized and opened. Actual testing shows that when the water tanks are full, opening solenoid valves SV3 and SV4 allows the water in the tanks to drain by gravity in approximately 24-26 seconds. For safety, the individual opening time for SV3 and SV4 is set to 30 seconds. After 30 seconds, the solenoid valves SV1 and SV2 at the top of the water tanks are triggered to open. At this point, all four solenoid valves (inlet and outlet) of the two water tanks are open. Compressed air in the main outlet pipe of the air compressor is discharged and blown into the atmosphere through the pressure guide pipe and water tanks, cleaning the pressure guide pipe and water tanks. This also removes moisture and dirt from the solenoid valve cores, ensuring normal operation next time.

[0192] The drainage process takes a total of 60 seconds. After 60 seconds, the solenoid valves SV3 and SV4 at the bottom of the water tank automatically close, while the solenoid valves SV1 and SV2 at the top of the water tank remain open. The water tank then returns to its normal state of storing condensate. After a 2-second wait, the automatic drainage process ends, and the program enters a new loop.

[0193] To prevent significant fluctuations in the air compressor flow rate during drainage, which could cause the air compressor to trip, and to prevent excessive differences in air compressor flow rate before and after drainage, which could lead to malfunction of the vent valve, the flow rate value FI101 of the flow indicator after temperature and pressure compensation calculation is locked 2 seconds before drainage begins. This ensures that the signal from the flow regulator FIC101 controlling the vent valve remains stable. Simultaneously, the real-time flow rate value after temperature and pressure compensation calculation is sent to register M1 and displayed on the process screen. The value of M1 is then compared with the locked FIC value to obtain the difference ΔF. Since the entire drainage process takes about 1 minute, under normal circumstances, the flow values ​​before and after drainage are basically the same. When the absolute value of the flow difference ΔF is less than 2% of the locked FI101 flow value, it indicates that the flow values ​​before and after drainage are stable and do not change much, so FI101 is unlocked, and FI101 will then monitor the flow value in real time. When the absolute value of ΔF is greater than or equal to 2% of the locked FI101 flow value, it indicates that the flow values ​​before and after drainage have changed significantly. In this case, FI101 remains locked and an alarm is triggered to alert the operator. At this time, the operator needs to intervene to confirm whether the production conditions have changed, make corresponding adjustments to the conditions, and then manually unlock the flow value of FI101 at the DCS operation station.

[0194] This invention provides a method for preventing water accumulation and freezing in the pressure-conducting pipe of an air compressor flow meter. A differential pressure switch is used to detect the pressure difference between the top and bottom of the water storage tank in the pressure-conducting pipe, determining the water level in the tank. A newly added logic program on the DCS terminal controls the opening and closing of the solenoid valves at the inlet and outlet of the added water storage tank, achieving an automatic drainage function. Before the condensate water level in the water storage tank of the air compressor flow meter pressure-conducting pipe affects the normal flow detection, the condensate water in the tank is automatically drained, preventing water accumulation and freezing in the pressure-conducting pipe that could affect the accuracy of air compressor flow detection. Simultaneously, this control logic program keeps the flow value stable during the automatic drainage process, preventing drastic fluctuations in the flow value and thus avoiding air compressor shutdown. Furthermore, it integrates various operating conditions and sets the control logic holistically.

[0195] In summary, the present invention provides a method for preventing water and ice formation in the pressure-conducting pipe of an air compressor flow meter. By modifying the sampling device of the air compressor flow transmitter, adding a differential pressure switch to detect the water level in the storage tank, adding a solenoid valve, and adding a logic control program, the method achieves automatic discharge when the storage tank is full. This eliminates the air compressor's accidental tripping and production stoppage caused by flow detection errors due to water in the pressure-conducting pipe of the air compressor flow transmitter, ensuring the stable operation of the air compressor equipment.

Claims

1. A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter, specifically targeting the flow transmitter section of an air compressor control system, characterized in that: By establishing control logic based on DCS settings, flow monitoring and control of the set flow transmitters are achieved, thereby enabling timely treatment of water stored in the pressure-conducting pipes. The flow transmitters configured include: Pressure guiding pipes are installed on both sides of the flow orifice plate in the outlet pipe of the air compressor; The pressure guiding pipe includes a positive pressure guiding pipe disposed on the inlet side of the flow orifice plate and a negative pressure guiding pipe disposed on the outlet side of the flow orifice plate; A first manual valve (V1), a pressure transmitter (PT101), a third manual valve (V3), a first solenoid valve (SV1), a first water storage tank (C1), and a third solenoid valve (SV3) are sequentially installed on the positive pressure side pressure guiding pipe. A second manual valve (V2), a fourth manual valve (V4), a second solenoid valve (SV2), a second water storage tank (C2), and a fourth solenoid valve (SV4) are sequentially installed on the negative pressure side pressure guiding pipe. A differential pressure transmitter (FT101) is installed on the pipe section between the positive pressure side guide pipe and the negative pressure side guide pipe, between the first manual valve (V1) and the third manual valve (V3), and on the pipe section between the corresponding second manual valve (V2) and the second solenoid valve (SV2). A first differential pressure switch (PDS1) is installed on the pipe section between the first solenoid valve (SV1) and the first water tank (C1) before the bottom of the first water tank (C1); a second differential pressure switch (PDS2) is installed on the pipe section between the second solenoid valve (SV2) and the second water tank (C2) before the bottom of the second water tank (C2).

2. The method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to claim 1, characterized in that: Flow monitoring and control are carried out in a manner that adapts to changes in operating conditions.

3. The method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to claim 2, characterized in that: The operating conditions include: normal drainage conditions and maintenance conditions; Normal drainage conditions and maintenance conditions are mutually exclusive operating states.

4. The method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to claim 2, characterized in that: The flow transmitters configured include: Pressure guiding pipes are installed on both sides of the flow orifice plate in the outlet pipe of the air compressor; The pressure guiding pipe includes a positive pressure guiding pipe disposed on the inlet side of the flow orifice plate and a negative pressure guiding pipe disposed on the outlet side of the flow orifice plate; A first manual valve (V1), a pressure transmitter (PT101), a third manual valve (V3), a first solenoid valve (SV1), a first water storage tank (C1), and a third solenoid valve (SV3) are sequentially installed on the positive pressure side pressure guiding pipe. A second manual valve (V2), a fourth manual valve (V4), a second solenoid valve (SV2), a second water storage tank (C2), and a fourth solenoid valve (SV4) are sequentially installed on the negative pressure side pressure guiding pipe. A differential pressure transmitter (FT101) is installed on the pipe section between the positive pressure side guide pipe and the negative pressure side guide pipe, between the first manual valve (V1) and the third manual valve (V3), and on the pipe section between the corresponding second manual valve (V2) and the second solenoid valve (SV2). A first differential pressure switch (PDS1) is installed on the pipe section between the first solenoid valve (SV1) and the first water tank (C1) before the bottom of the first water tank (C1); a second differential pressure switch (PDS2) is installed on the pipe section between the second solenoid valve (SV2) and the second water tank (C2) before the bottom of the second water tank (C2).

5. The method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to claim 4, characterized in that: The operating conditions include: normal drainage conditions and maintenance conditions; Normal drainage conditions and maintenance conditions are mutually exclusive operating states.

6. The method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to claim 3, characterized in that: The operating conditions also include: switching the flow transmitter on / off operating condition, alarm and alarm post-processing operating condition.

7. The method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to claim 5, characterized in that: The operating conditions also include: switching the flow transmitter on / off operating condition, alarm and alarm post-processing operating condition.

8. The method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to claim 5, characterized in that: The specific steps for monitoring and controlling flow based on normal drainage conditions are as follows: S1: Open the first manual valve (V1), the second manual valve (V2), the third manual valve (V3), the fourth manual valve (V4), the first solenoid valve (SV1), and the second solenoid valve (SV2); close the third solenoid valve (SV3) and the fourth solenoid valve (SV4); when either the first water tank (C1) or the second water tank (C2) is detected to be full, the corresponding differential pressure switch sends a water tank full signal to the DCS; S2: After receiving the full water signal, the DCS issues a drainage command. According to the drainage command, the first solenoid valve (SV1) and the second solenoid valve (SV2) are triggered to close, and the third solenoid valve (SV3) and the fourth solenoid valve (SV4) are triggered to open. S3: After the DCS issues a drainage command within a set time, the DCS issues a purging command, which triggers the opening of the first solenoid valve (SV1) and the second solenoid valve (SV2). S4: After a set time following the issuance of the purging command by the DCS, the DCS outputs a command indicating the completion of one drainage process. Based on the command, the third solenoid valve (SV3) and the fourth solenoid valve (SV4) are triggered to close, and the flow monitoring and control of the next cycle begins.

9. A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to claim 5, characterized in that: The specific steps for monitoring and controlling flow based on maintenance conditions are as follows: SS1: After receiving the maintenance signal, the DCS issues a standby command. According to the standby command, the first manual valve (V1), the second manual valve (V2), the third manual valve (V3), the fourth manual valve (V4), the third solenoid valve (SV3), and the fourth solenoid valve (SV4) are closed, while the first solenoid valve (SV1) and the second solenoid valve (SV2) remain open. SS2: After maintenance is completed, the DCS receives the purging signal and issues a forced drainage command accordingly. According to the forced drainage command, the first manual valve (V1), the second manual valve (V2), the third manual valve (V3), the fourth manual valve (V4), the third solenoid valve (SV3), and the fourth solenoid valve (SV4) are opened, and the first solenoid valve (SV1) and the second solenoid valve (SV2) are kept open. After the set time, the third solenoid valve (SV3) and the fourth solenoid valve (SV4) are closed to complete the maintenance operation.

10. A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to claim 7, characterized in that: The flow monitoring and control system, based on alarm and post-alarm processing conditions, follows these steps: SA1: The set time before the DCS issues the drain command locks the flow value FI101 of the flow indicator after temperature and pressure compensation calculation in the air compressor control system, so that the flow indicator regulator FIC101 controls the vent valve signal to remain stable. SA2: Send the real-time flow value after temperature and pressure compensation calculation to register M1, and compare the real-time value sent to M1 with the locked flow value FI101 in real time to obtain a set of differences △F in the time series; SA3: Compare the absolute value of each ΔF with 2% of the locked flow value FI101. If the absolute value is less than 2% of the locked flow value FI101, then unlock the flow indicator value and perform normal monitoring. Otherwise, an alarm will be triggered.

11. The method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to claim 10, characterized in that: The real-time value sent to register M1 in step SA2 starts from the moment the flow rate value FI101 of the flow indicator is locked and continues until the drainage is completed.

12. The method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to claim 10, characterized in that: The "set time before the DCS issues the drainage command" mentioned in step SA1 is specifically 2 seconds before the DCS issues the drainage command.

13. The method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to claim 8, characterized in that: The "monitoring and control of flow rate in the next cycle" in step S4 is performed 2 seconds after the third solenoid valve (SV3) and the fourth solenoid valve (SV4) are closed.

14. The method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to claim 8, characterized in that: In step S3, the set time for "DCS issues a purging command after the set time for DCS to issue a drainage command" is set by adding 4-6 seconds to the theoretical emptying time of the water storage tank.

15. A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to claim 3 or 5, characterized in that: Normal drainage operation is based on automatic mode; Maintenance operations are performed in manual mode.

16. A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to claim 2 or 4, characterized in that: The first solenoid valve (SV1), the second solenoid valve (SV2), the third solenoid valve (SV3), and the fourth solenoid valve (SV4) are all remotely wirelessly controlled for on / off switching.

17. A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to claim 9, characterized in that: In step SS1, the DCS receives manually issued maintenance signals based on the configured human-machine interface.

18. A method for preventing water from entering and freezing inside the pressure-conducting pipe of an air compressor flow meter according to claim 10, characterized in that: The "unlocking of the flow indicator flow value" mentioned in step SA3 is achieved manually through the human-computer interaction interface.

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