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Analysis of Common Problems in Application of Control Valve in Industry
Regulating valve is particularly important in industrial production and very common control equipment, it is working properly or not directly related to the normal production of the entire device or not. At present, with the rapid development of control valve technology, the manufacturer and form of control valve are very numerous and have different functions. The following focuses on the common problems that various types of control valves should pay attention before installation and operation. Control valve hydraulic test The hydraulic test of the valve body includes the pressure test of the valve body and the leak test of the valve when the valve is fully closed. Typically, when the design pressure exceeds 10MPa control valve, the valve body must be pressure test to check the pressure on the valve body itself and the valve cover. 1, the control valve pressure test should pay attention to the problem 1) regulating valve body pressure test Manual pressure test pump hydraulic test, the use of electric pressure test pump is strictly prohibited. 2) The test medium is clean water. 3) The test pressure is 1.25 times of the design pressure. 4) pressure test pressure gauge should be verified, the accuracy should not be less than 1.5, the upper limit of the scale should be 1.5 to 2 times the test pressure. 5) Open the air valve in the pressure test valve when the valve core open at least 20% of the opening, it must be kept in mind to prevent excessive pressure on one side of the valve to damage. Under normal circumstances, the control valve spool is allowed to a certain amount of leakage, according to the difference between the control valve leakage level, generally only requires the high differential pressure control valve (V, VI leakage) leak test. 2, Leakage test should pay attention to the problem 1) regulating valve body pressure test using a manual pressure test pump hydraulic test, the use of electric pressure test pump is strictly prohibited (VI leaking valve using air pressure test) 2) test medium is clean Of water (Class VI leak valve with clean air). 3) Leakage rating The test pressure is the maximum differential pressure that the valve is designed to work on (see design parameters). 4) pressure test pressure gauge should be verified, the accuracy should not be less than 1.5, the upper limit of the scale test pressure of 1.5 to 2 times. 3, the adjustment of the valve regulating the newly installed pneumatic control valve should be installed before the monomer adjustment. Adjustment should reach the performance indicators: Basic error: ± 1.5% Return error: 1.5% Insensitive area: 0.6% Now, the valve valve and the electrical valve positioner manufacturers are many, different functions, the electrical valve positioner trend In the intelligent, specific adjustment methods are different, not repeat them here. 4, the installation of regulating valve The installation of regulating valve is the key issue should be noted that the quality of the installation is directly related to the commissioning of the valve and performance. The following problems should be observed during the installation: 1) The valve must be carefully cleaned of accumulated dust during storage before installation, and should be kept clean during installation. Damage to the valve seat and trim due to dirt and dust. To protect the cleaning, it is usually possible to attach flaps to the ends of open flanges that are not welded on the same day. 2) When the control valve is installed, the arrow on the valve body should be consistent with the medium flow direction. 3) Control valve is a precision component, if they are subject to pipe deformation stress, will destroy the normal work. Therefore, flange and pipe installation should be vertical and accurate position to avoid pipe deformation. Well, the pipe should be properly supported to prevent it from buckling under the weight of the valve. 4) The control valve must be used with the pipeline with special care. If the control valve and pipe welding attention is not enough, failed to eliminate the stress, it will have deformation. Welding, welding slag must be strictly avoided splashing into the valve, the presence of welding slag detrimental to the performance of the valve, if the splash splashed directly on the spool, ranging from a direct impact on the control valve action, heavy damage spool and seat. 5) When the pipeline is under pressure test and blow-off, the control valve should be removed and connected with the corresponding straight pipe section to prevent debris such as welding slag and iron cutting from getting stuck between the valve core and the valve seat. Remove the valve opening flange end of the plastic wrap tightly. 5, the control valve linkage test control valve installed in the device must be linked before the test drive. Joint test should focus on the following points: 1) control valve linkage test process before the pipeline must be rigorously purged and qualified to purge unqualified pipeline is strictly prohibited to install the control valve, because the pipeline residues such as welding slag, dust, etc. Hard debris will damage the valve seat and seat sealing surface. 2) Butterfly valve should be checked before the linkage at both ends of the valve should not be pressure test or blind seal. 3) Control valve with handwheel mechanism, handwheel mechanism should be in "release" position. Check the air supply valve pressure regulator valve to meet the gas requirements. 6, in the process of installation of industrial automation instruments, regulating valve installation and commissioning of the most complex, most difficult and most prone to problems. Throughout the process, instrumentation and pipe professional should be coordinated with each other, with each other, work closely with the problems promptly resolved in a timely manner, in strict accordance with the requirements, according to the rules of operation, the only way to successfully ensure the quality of the installation and commissioning valve quality control In order to ensure the smooth progress of the entire installation project and the smooth operation of the entire industrial plant.