Analysis of 16 standards and common problems that should be followed in valve hydrostatic test

Analysis of 16 standards and common problems that should be followed in valve hydrostatic test

The manufacture of valves is a complex and simple process. The production cycle of valves such as globe valves, valves and disc valves is generally in three days. The valves must be tested for all kinds of characteristics. Pressure test is sichuan valve can bear the pressure value is not to meet the requirements of production and manufacturing requirements, the general valve water pressure test must follow the following standards and common problems:

(1) Under normal circumstances, the valve is not made compressive strength test, but after the repair of the oil circuit plate and single flow valve or the oil circuit plate and single flow valve damaged by erosion should be made compressive strength test. For valves, the uniform and return pressure and other tests shall conform to the requirements of their use instructions and related specifications.
(2) The valve assembly should be tested for compressive strength and sealing. Low voltage valve sampling inspection 20%, such as unqualified should be 100% inspection; Medium and high pressure valves should be 100% inspected.
(3) During the test, the valve assembly part should be in a very easy to carry out the inspection position.
(4) the valve of electric welding connection type, when the water pressure test of huang plate is not good, the cone sealing or O-ring sealing can be used to carry out the water pressure test.
(5) When the hydraulic press test, the valve gas will be removed as far as possible.
(6) The pressure should be increased slowly during the test, and it is not allowed to increase the pressure greatly and suddenly.
(7) The compressive strength test and sealing type test duration is generally 2 — 3min, the key and unique valve should continue for 5min. The test duration of small diameter valves can be shorter, and the test duration of large diameter valves can be longer. During the whole process of the test, if there is any doubt, the test time can be extended. During the compressive strength test, the oil circuit plate and the single flow valve shall not be allowed to sweat or leak. Sealing test, the general valve is only completed once, valves, high-pressure valves and other raw valves need to carry out 2 times. When the test, low voltage, large diameter of the unimportant valve and its requirements to allow water leakage valve, allow a small amount of water seepage; Because the regulations for general valves, power plant valves, Marine valves and other valves are different, the leakage regulations should be implemented according to the relevant requirements.
(8) One-way throttle valve is not closed parts of the sealing test, but the compressive strength test and packing material and gasket sealing test.
(9) In the hydrostatic test, the valve closing force only allows one person’s normal energy to close; Do not rely on special tools such as bars (except torque wrenches) for shock absorption, when the spindle aperture exceeds up to 320mm, allow two people to turn off.
(10) the valve with upper sealing should be removed from the filling material for sealing test, sealing officer closed, check whether it is leaking. When using steam body for test, fill water in explosion-proof junction box for inspection. For sealing test of filling material, sealing is not allowed in close parts.
(11) Any valve with pushing equipment, test its sealing using pushing equipment to close the valve to carry out sealing test. When the enemy moves to push the equipment, the sealing test of the valve should also be carried out.
(12) the compressive strength test and sealing test are installed on the inlet valve of the distribution valve, and the compressive strength and sealing test is carried out in the distribution valve; When the distribution valve is opened, it should also be opened.
(13) When pig iron valve compressive strength test, use copper hammer to pat oil circuit plate and single flow valve, check whether there is water leakage.
(14) valve test, in addition to the plug valve is required to allow oil on the surface, other valves are not allowed to oil test on the surface.
(15) valve hydraulic test, valve flange on the valve clamping force is not suitable for too large, in order to prevent the valve deformation, harm the actual effect of the test (pig iron valve if pressed too tight, will continue to damage).
(16) After the completion of the hydraulic test of the valve, the water seepage in the valve should be cleaned immediately, and the test record should be made.
Valve hydrostatic test is the inspection must be carried out before leaving the factory, which can ensure the reliable operation of the valve. Here it is suggested that valve manufacturers hydrostatic test staff to maintain their own safety, in recent years, valve hydrostatic test safety accidents, should pay attention to.
Pneumatic butterfly valve diaphragm valve compressive strength test from either end of the introduction of material, medium to open the piston valve, the other end of the closed, the test pressure rose to the standard value, see oil plate and single flow valve no leakage for qualified. Then lower the blood pressure to the sealing test pressure, close the piston valve, open the other end to carry out inspection, no leakage is qualified. Check valve check valve test condition: adjustment
Pneumatic butterfly valve
Diaphragm valve compressive strength test from either end of the introduction of material, medium to open the piston valve, the other end of the closed, test pressure rose to the standard value, see oil plate and single flow valve no leakage for qualified. Then lower the blood pressure to the sealing test pressure, close the piston valve, open the other end to carry out inspection, no leakage is qualified.
Check valve
Check valve test: lift type check valve piston valve center line is located in the vertical part; Swing check valve safety channel centerline and piston valve centerline are located in parallel with the straight line.
Compressive strength test, from the entrance of the end of the introduction of the test material to the standard value, the other end of the closed, see oil circuit plate and single flow valve no leakage for qualified.
Sealing test from the export end of the introduction of test material, at the entrance of the end of the inspection surface, filling material and gasket no leakage for qualified.
The valve
The compressive strength of the relief valve is tested with tap water, as with other valves. When testing the bottom of the oil circuit plate, the pressure is introduced from the end of the inlet, and the surface is closed; When testing the upper end of the oil circuit board and the single flow valve, the pressure is introduced from the outlet end, and the other end is closed. No leakage of oil circuit board and single flow valve in the required time period is qualified.
Sealing test and uniform test, the general application of material is: steam valve to superheated steam as the test material; Ammonia or other steam valve with gas as the test material; Water and other non – corrosive liquid valves to water as the test material. For some key parts of the valve common hydrogen as the test material.
Sealing test is carried out with nominal diameter pressure numerical test pressure, the frequency of which is not less than 2 times, no leakage in the required time period is qualified. There are two ways to check leakage: one is the sealing of the valve joints, with unsalted butter to seal the plastic paper towel on the export flange, plastic paper for leakage, not convex for qualified; The second is to use unsalted butter to thin plastic plate or other plate sealing towel in the export flannel below, sealing piston valve water injection, detection of bubbles in the water is qualified.
Valve uniform and back seat pressure test frequency is not less than 3 times, meet the requirements for qualified.
The pressure regulating valve
The compressive strength test of the pressure reducing valve is generally assembled after the test of parts, but also after the test of assembly. Duration of compressive strength test: DN50mm for 1min; DN65~150mm more than 2min; DN150mm for more than 3 minutes. After welding the metal bellows with the parts, the compressive strength test is carried out with gas 1.5 times the higher pressure behind the valve.
The sealing test should be carried out according to the substance in real work. When using gas or water test, carry out the test at 1.1 times of nominal diameter pressure; Steam tests are carried out at very high operating pressures at operating temperatures. The difference between inlet pressure and outlet pressure is not less than 0.2mpa.
The test method is: after the inlet pressure control precision, slowly adjust the valve adjustment screw, so that the outlet pressure in the very large and small value category can be dexterously, continuously change, there is no stagnation, stuck. For the steam pressure reducing valve, when the inlet pressure is adjusted away, close the valve and disconnect the valve, the outlet pressure is relatively high and relatively low value, within 2 minutes, the value increment of the outlet pressure should meet the requirements in Table 6-22, at the same time, the pipe capacity after the valve meets the requirements in Table 6-23 is qualified; For water and air pressure reducing valve, when the inlet pressure control accuracy, the outlet pressure is zero, close the pressure regulating valve to carry out sealing test, no leakage in 2min is qualified.
The method of pressure and total flow characteristic test is to adjust the inlet and outlet pressure first, change 30% of the total flow of the outlet under the pressure difference here, or change 30% of the inlet pressure without moving the total flow, then measure the outlet pressure accurately, and its partial value is qualified in line with the requirements in Table 6-24.
Steam trap
There are many forms of steam trap, and there are many new test items. Generally, only pressure compressive strength test, compressive strength test and posture test are used. The compressive strength test is the same as other valves.
The compression test is to carry out the pressure compression test on the pressure switch of water pump and other closed parts with the pressure of 1.2 times the nominal diameter pressure.
The test is to replace into steam and saturated water, the test frequency is not less than 3 times. The test pressure is carried out at very high working pressure, very low working pressure and very low working pressure respectively. Dexterity in posture and lack of steam are qualified. The postural test and sealing test of steam trap are usually carried out in the laboratory.
Steam trap in addition to the pressure test, the compressive strength test, compression test and posture have hot condensate displacement experiment, super-cooling degree, relatively large allow the back pressure type rate test, the leakage rate experiment, exhaust gas and relatively low working pressure in the test, the relatively high work pressure test, etc, depending on has the condition.