1. The regulating valve is a very common and particularly important control device in industrial production. Whether it works normally or not is directly related to the normal production of the whole device. At present, with the rapid development of the control valve technology, the manufacturers and forms of the regulating valve are very diverse, and the functions are also different. The following focuses on the common problems that should be paid attention to before the installation and commissioning of various types of regulating valves.
2. The incoming inspection of the incoming inspection control valve before the installation of the regulating valve is a very important part to confirm whether the arrival condition of the regulating valve meets the design requirements. Each technical requirement of the regulating valve should meet the design requirements, but the following items should be carefully checked during the incoming inspection.
2.1, valve body / valve trim specifications This content mainly includes: valve type, valve type, nominal diameter, seat size, spool form, flow characteristics, leakage level, valve body material, spool material, seat material , CV value, flange standard grade size and sealing surface form, as long as it is found that the same content and design inconsistency should be identified and recognized by the design.
2.2. Some parts of the actuator should check the type, type, mode of action, spring range, air supply pressure, etc. of the actuator.
2.3. Positioner Part This item mainly checks the input signal of the positioner, the pressure of the air source, the size of the electrical and air source interface and the explosion-proof level, and the explosion-proof level must not be lower than the design level.
2.4. The accessories carefully clean all accessories according to the design technical requirements of the regulating valve, such as filter pressure reducing valve, valve position switch, solenoid valve, hand wheel mechanism and special tools. The inspection of the above items can be achieved by means of cleaning, measuring instruments, viewing nameplates and special inspection means (such as flange and bolt materials can be identified by spectral analysis).
3. Regulating valve hydraulic pressure test The hydraulic pressure test of the valve body includes the pressure test of the valve body and the leak test when the valve core is fully closed. Normally, when designing a regulating valve with a pressure exceeding 10 MPa, the valve body must be subjected to a withstand voltage test to check the withstand voltage of the valve body itself and the upper valve cover.
3.1. The problems that should be paid attention to when adjusting the pressure test of the valve (1) The pressure test of the valve body of the regulating valve is carried out by a manual pressure test pump, and the electric pressure test pump is strictly prohibited.
(2) The test medium is clean water.
(3) The test pressure is 1.25 times the design pressure.
(4) The pressure gauge used for the pressure test shall be qualified. The accuracy shall not be less than 1.5, and the upper limit of the scale shall be 1.5 to 2 times the test pressure.
(5) The valve opening of the valve is at least 20% open when the pressure test of the valve is performed. This must be kept in mind to prevent the valve core from being damaged due to excessive pressure on one side. Normally, the regulating valve spool is allowed to have a certain amount of leakage. According to the difference in the leakage level of the regulating valve, it is generally only required to perform a leak test on the high differential pressure regulating valve (V, VI leakage).
3.2. Problems that should be paid attention to during the leakage test (1) Pressure test of the valve body of the regulating valve The hydraulic pressure test is carried out by using a manual pressure test pump. It is strictly forbidden to use the electric pressure test pump (the pressure test of the VI-level leaking valve).
(2) The test medium is clean water (the valve of Class VI leakage uses clean air).
(3) Leakage level The test pressure is the large difference pressure (see design parameters) designed when the valve is working.
(4) The pressure gauge used for the pressure test shall be qualified. The accuracy shall not be less than 1.5, and the upper limit of the scale shall be 1.5 to 2 times the test pressure.
4. Monomer adjustment of the regulating valve The newly installed pneumatic regulating valve should be adjusted before the installation. Performance indicators that should be achieved: basic error: ±1.5% return error: 1.5% insensitive area: 0.6% Today, there are many manufacturers of detent valves and electric valve positioners, with different functions, and the trend of electric valve positioners In terms of intelligence, the specific adjustment methods are different, and will not be described here.
5, the installation of the regulating valve The installation of the regulating valve is a key issue to be noted. The quality of the installation is directly related to the commissioning and performance of the regulating valve. The following issues should be noted during the installation process:
(1) Before the valve is installed, the dust accumulated during the storage of the valve must be carefully removed and kept clean during the installation process. Damage to the seat and trim due to dusty impurities. In order to protect the cleaning, it is usually possible to attach a cover to the end of the open flange which is not welded on the day.
(2) When the regulating valve is installed, the arrow on the valve body should be consistent with the flow direction of the medium.
(3) Regulating valves are precision components that will undermine normal operation if they are stressed by pipe deformation. Therefore, the flange and pipe installation should be vertical and positionally accurate to avoid deformation of the pipe. Well, the pipe should be properly supported to prevent it from bending and deforming under the weight of the valve.
(4) The regulating valve must be specially handled when welding to the pipe. If the control valve is not adequately welded to the pipe and the stress is not removed, deformation will occur. When welding, the welding slag must be strictly prevented from splashing into the valve. The presence of the welding slag will damage the performance of the valve. If the splash directly splashes on the valve core, it will directly affect the action of the regulating valve, and damage the valve core and the valve seat.
(5) When the pipeline is tested and blown out, the regulating valve should be removed and connected with the corresponding straight pipe section to prevent the welding slag, iron cutting and other debris from getting stuck between the valve core and the valve seat. The end of the flange of the removed regulator valve is tightly wrapped with plastic sheeting.
6. The linkage test of the regulating valve The regulating valve must be tested before the device is installed. The linkage test should focus on the following points:
(1) Before the control valve linkage test, the process piping must pass the strict purge and pass the test. It is strictly forbidden to install the regulating valve for the unqualified pipeline, because the residue in the pipeline such as welding slag, dust and other hard objects will damage the valve core. Seals the surface with the seat.
(2) Before the butterfly valve is linked, it should be checked that the two ends of the valve should not be tested or blocked.
(3) With the adjustment valve of the handwheel mechanism, the handwheel mechanism should be in the "release" position. Check if the supply pressure of the pressure reducing valve reaches the air supply requirement of each regulating valve.
7, in the process of industrial automation instrument installation, the installation and commissioning of the control valve is complex, zui is difficult and zui is prone to problems. In the whole process, the instrument professional and the pipeline professional should coordinate with each other, support each other, closely cooperate, and promptly reflect the problems in a timely manner, strictly follow the requirements and operate according to the regulations. Only in this way can the installation quality and commissioning quality of the regulating valve be smoothly ensured. In order to ensure the smooth progress of the entire installation project and the smooth operation of the entire industrial plant.
2. The incoming inspection of the incoming inspection control valve before the installation of the regulating valve is a very important part to confirm whether the arrival condition of the regulating valve meets the design requirements. Each technical requirement of the regulating valve should meet the design requirements, but the following items should be carefully checked during the incoming inspection.
2.1, valve body / valve trim specifications This content mainly includes: valve type, valve type, nominal diameter, seat size, spool form, flow characteristics, leakage level, valve body material, spool material, seat material , CV value, flange standard grade size and sealing surface form, as long as it is found that the same content and design inconsistency should be identified and recognized by the design.
2.2. Some parts of the actuator should check the type, type, mode of action, spring range, air supply pressure, etc. of the actuator.
2.3. Positioner Part This item mainly checks the input signal of the positioner, the pressure of the air source, the size of the electrical and air source interface and the explosion-proof level, and the explosion-proof level must not be lower than the design level.
2.4. The accessories carefully clean all accessories according to the design technical requirements of the regulating valve, such as filter pressure reducing valve, valve position switch, solenoid valve, hand wheel mechanism and special tools. The inspection of the above items can be achieved by means of cleaning, measuring instruments, viewing nameplates and special inspection means (such as flange and bolt materials can be identified by spectral analysis).
3. Regulating valve hydraulic pressure test The hydraulic pressure test of the valve body includes the pressure test of the valve body and the leak test when the valve core is fully closed. Normally, when designing a regulating valve with a pressure exceeding 10 MPa, the valve body must be subjected to a withstand voltage test to check the withstand voltage of the valve body itself and the upper valve cover.
3.1. The problems that should be paid attention to when adjusting the pressure test of the valve (1) The pressure test of the valve body of the regulating valve is carried out by a manual pressure test pump, and the electric pressure test pump is strictly prohibited.
(2) The test medium is clean water.
(3) The test pressure is 1.25 times the design pressure.
(4) The pressure gauge used for the pressure test shall be qualified. The accuracy shall not be less than 1.5, and the upper limit of the scale shall be 1.5 to 2 times the test pressure.
(5) The valve opening of the valve is at least 20% open when the pressure test of the valve is performed. This must be kept in mind to prevent the valve core from being damaged due to excessive pressure on one side. Normally, the regulating valve spool is allowed to have a certain amount of leakage. According to the difference in the leakage level of the regulating valve, it is generally only required to perform a leak test on the high differential pressure regulating valve (V, VI leakage).
3.2. Problems that should be paid attention to during the leakage test (1) Pressure test of the valve body of the regulating valve The hydraulic pressure test is carried out by using a manual pressure test pump. It is strictly forbidden to use the electric pressure test pump (the pressure test of the VI-level leaking valve).
(2) The test medium is clean water (the valve of Class VI leakage uses clean air).
(3) Leakage level The test pressure is the large difference pressure (see design parameters) designed when the valve is working.
(4) The pressure gauge used for the pressure test shall be qualified. The accuracy shall not be less than 1.5, and the upper limit of the scale shall be 1.5 to 2 times the test pressure.
4. Monomer adjustment of the regulating valve The newly installed pneumatic regulating valve should be adjusted before the installation. Performance indicators that should be achieved: basic error: ±1.5% return error: 1.5% insensitive area: 0.6% Today, there are many manufacturers of detent valves and electric valve positioners, with different functions, and the trend of electric valve positioners In terms of intelligence, the specific adjustment methods are different, and will not be described here.
5, the installation of the regulating valve The installation of the regulating valve is a key issue to be noted. The quality of the installation is directly related to the commissioning and performance of the regulating valve. The following issues should be noted during the installation process:
(1) Before the valve is installed, the dust accumulated during the storage of the valve must be carefully removed and kept clean during the installation process. Damage to the seat and trim due to dusty impurities. In order to protect the cleaning, it is usually possible to attach a cover to the end of the open flange which is not welded on the day.
(2) When the regulating valve is installed, the arrow on the valve body should be consistent with the flow direction of the medium.
(3) Regulating valves are precision components that will undermine normal operation if they are stressed by pipe deformation. Therefore, the flange and pipe installation should be vertical and positionally accurate to avoid deformation of the pipe. Well, the pipe should be properly supported to prevent it from bending and deforming under the weight of the valve.
(4) The regulating valve must be specially handled when welding to the pipe. If the control valve is not adequately welded to the pipe and the stress is not removed, deformation will occur. When welding, the welding slag must be strictly prevented from splashing into the valve. The presence of the welding slag will damage the performance of the valve. If the splash directly splashes on the valve core, it will directly affect the action of the regulating valve, and damage the valve core and the valve seat.
(5) When the pipeline is tested and blown out, the regulating valve should be removed and connected with the corresponding straight pipe section to prevent the welding slag, iron cutting and other debris from getting stuck between the valve core and the valve seat. The end of the flange of the removed regulator valve is tightly wrapped with plastic sheeting.
6. The linkage test of the regulating valve The regulating valve must be tested before the device is installed. The linkage test should focus on the following points:
(1) Before the control valve linkage test, the process piping must pass the strict purge and pass the test. It is strictly forbidden to install the regulating valve for the unqualified pipeline, because the residue in the pipeline such as welding slag, dust and other hard objects will damage the valve core. Seals the surface with the seat.
(2) Before the butterfly valve is linked, it should be checked that the two ends of the valve should not be tested or blocked.
(3) With the adjustment valve of the handwheel mechanism, the handwheel mechanism should be in the "release" position. Check if the supply pressure of the pressure reducing valve reaches the air supply requirement of each regulating valve.
7, in the process of industrial automation instrument installation, the installation and commissioning of the control valve is complex, zui is difficult and zui is prone to problems. In the whole process, the instrument professional and the pipeline professional should coordinate with each other, support each other, closely cooperate, and promptly reflect the problems in a timely manner, strictly follow the requirements and operate according to the regulations. Only in this way can the installation quality and commissioning quality of the regulating valve be smoothly ensured. In order to ensure the smooth progress of the entire installation project and the smooth operation of the entire industrial plant.
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