Brief Analysis on Some Problems Should Be Noticed in Installation and Operation of Control Valve
Regulating valve installation and operation should pay attention to several issues 1 is a very common and particularly important industrial production control equipment, it is working properly or not directly related to the normal production of the entire device or not. At present, with the ever-changing technology, the manufacturers and forms are numerous and their functions are also different. The following focuses on the common problems that should be noticed before installation and commissioning. 2 Pre-installation purchase inspection incoming purchase inspection is a very important part to confirm the arrival of the product meets the design requirements. Of each technical requirements should meet the design requirements, but the purchase inspection should focus on checking the following content. 2.1 Body / Trim Specifications This item 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, etc., as long as they found that one of the same content and design are inconsistent design should be identified and approved. 2.2 The implementing agency part of the main content should check the executing agency type, type, form of action, spring range, supply pressure. 2.3 Locator This section mainly checks the positioner input signal, air pressure, electrical and gas source interface size and explosion-proof rating, of which explosion-proof rating may not be less than the design level requirements. 2.4 Accessories According to the design and technical requirements carefully clean the various accessories, such as filtration, valve position switch ,, hand wheel mechanism, special tools. The above contents of the inspection can be cleaned, measuring instruments, check the nameplate and special testing methods (such as flange and bolt material can be identified by spectroscopy) and other methods to achieve. 3 Water pressure 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. Under normal circumstances, when the design pressure exceeds 10MPa, the body must be pressure test to test the valve body itself and the pressure on the valve cover. 3.1 pressure test should pay attention to the problem (1) body pressure test Manual pressure test pump hydraulic test, the use of electric pressure test pump is strictly prohibited. (2) 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) Air-Opened Valve When the pressure-proof test of the valve is carried out, the valve plug opens at least 20% of the opening degree. It must be kept in mind that the valve plug is prevented from being over-pressurized and damaged. Under normal circumstances, the spool is allowed to a certain amount of leakage, according to the difference between the level of leakage, generally only requires the high differential pressure (V, Level VI leakage) leak test. 3.2 Leakage test should pay attention to the problem (1) body pressure test manual pressure test pump hydrostatic test, the use of electric pressure test pump (Class VI leak valve pressure test). (2) The test medium is clean water (class VI leaking valves use clean air). (3) Leakage rating The test pressure is the maximum differential pressure designed for the valve operation (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. ? 4 monomer adjustment New installation of the pneumatic installation should be carried out before the monomer adjustment. Adjustment should reach the performance indicators: Basic error: ± 1.5% Return error: 1.5% Insensitive area: 0.6% Now, there are many valve manufacturers and electrical positioner, different functions, the electrical valve positioner tends to Intelligent, specific adjustment methods are different, not repeat them here. 5 installation is the key installation should pay attention to the problem, the quality of the installation is directly related to the commissioning and performance. The following problems should be observed during the installation: (1) The valve must be carefully cleaned of accumulated dust during installation and 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 installing, the arrow on the valve body should be consistent with the medium flow direction. (3) are precision components that, if they are stressed by pipe deformation, will disrupt normal operation. 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) Particular care must be taken when welding with pipes. If the pipe welding is not enough attention, failed to eliminate the stress, it will produce deformation. Welding, welding slag must be strictly avoided splashing into the valve, the presence of welding slag loss of performance, if the splash splashed directly on the spool, ranging from direct impact on the action, will damage the spool and valve seat. (5) When the pipe is under pressure test and blowing off, it 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 valve seat. Remove the open flange end of the plastic wrap tightly. 6 linkage test in the installation of the device before driving must be linked test. Interaction test should focus on the following points: (1) Before the linkage test process piping must be rigorously purged and qualified, purging unqualified pipe is strictly prohibited installation, because the pipeline residues such as welding slag, dust and other hard miscellaneous Material will damage the valve seat and seat sealing surface. (2) before the linkage should check both ends of the valve should not be pressure test or blind seal. (3) With the hand wheel mechanism, hand wheel mechanism should be in a "release" position. Check if the air supply pressure meets the air supply requirements. 7 Conclusion In the process of installation of industrial automation instruments, the installation and operation of the most complex, the 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 reflect the timely manner resolved in strict accordance with the requirements of the operation, according to the rules and regulations, the only way to successfully ensure the quality of the installation and operation quality assurance The smooth installation of the entire project and the smooth operation of the entire industrial plant. More keyword search: control valve
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