Inspection before valve installation
① Carefully check whether the valve model and specification meet the drawing requirements.
② Check whether the valve rod and valve disc can be opened flexibly, and whether they are stuck or skewed.
③ Check whether the valve is damaged and whether the thread of threaded valve is correct and complete.
④ Check whether the connection between valve seat and valve body is firm, and the connection between valve disc and valve seat, valve cover and valve body, and valve rod and valve disc.
⑤ Check whether the valve gasket, packing and fasteners (bolts) are suitable for the requirements of the nature of the working medium.
⑥ The pressure reducing valve that is old or has been put aside for a long time shall be dismantled, and the dust, sand and other sundries shall be cleaned with water.
⑦ Remove the vent cover and check the sealing degree. The valve disc must be closed tightly.
Pressure test of valve
Strength test and tightness test shall be carried out for low pressure, medium pressure and high pressure valves, and spectral analysis shall be carried out for alloy steel valves one by one to recheck the material.
1. Strength test of valve
The strength test of the valve is to check the leakage of the external surface of the valve when the valve is open. For valves with PN ≤ 32MPa, the test pressure is 1.5 times of the nominal pressure, the test time is not less than 5min, and there is no leakage at the shell and packing gland.
2. Tightness test of valve
For the test conducted under the fully closed state of the valve, check whether there is leakage on the sealing surface of the valve. The test pressure of the valve, except
Butterfly Valve,
Check Valve, bottom valve and throttle valve, should generally be carried out at the nominal pressure. When the working pressure can be determined, the test can also be carried out at 1.25 times of the working pressure, and the valve disc sealing surface is qualified if there is no leakage.
General regulations for valve installation
1. The installation position of the valve shall not interfere with the operation, disassembly and maintenance of the equipment, pipeline and valve body itself, while taking into account the beauty of the assembly appearance.
2. The valve on the horizontal pipe shall be installed with the valve stem upward or inclined at a certain angle, and the handwheel shall not be installed downward. The valve, valve rod and handwheel on the high altitude pipeline can be installed horizontally, and the valve can be opened and closed remotely by using the vertical chain.
3. Arranged symmetrically, neat and beautiful; For the valve on the riser, if the process allows, the valve handwheel is the most suitable for operation at the height of chest height, generally 1.0-1.2m from the ground, and the valve rod must be installed in the direction of the operator.
4. For the valves on the parallel riser, the centerline elevation should be consistent, and the clear distance between the hand wheels should not be less than 100mm; The valves on the parallel horizontal pipes shall be staggered to reduce the pipe spacing.
5. When installing heavy valves on water pumps, heat exchangers and other equipment, valve supports shall be provided; When the valve is operated frequently and installed more than 1.8m from the operating surface, a fixed operating platform shall be set.
6. If there is an arrow mark on the valve body, the direction of the arrow is the flow direction of the medium. When installing the valve, pay attention to make the arrow point in the same direction as the medium in the pipe.
7. When installing flange valves, ensure that the two flange end faces are parallel and concentric with each other, and do not use double gaskets.
8. When installing threaded valves, a threaded valve shall be equipped with a union to facilitate disassembly. The setting of the union should consider the convenience of maintenance. Usually, the water flows through the valve first and then through the union.
Precautions for valve installation
1. The valve body material of the valve is mostly made of cast iron, which is brittle, so it shall not be impacted by heavy objects.
2. It is not allowed to throw the valve when carrying it; When lifting and hoisting the valve, the rope shall be tied to the valve body, and it is strictly prohibited to tie it to the hand wheel, valve rod and flange bolt hole.
3. The valve shall be installed at the most convenient place for operation, maintenance and overhaul, and it is strictly prohibited to be buried underground. The valve on the pipeline directly buried and in the trench shall be provided with an inspection chamber to facilitate the opening, closing and adjustment of the valve.
4. Ensure that the thread is intact, and wrap hemp, lead oil or polytetrafluoroethylene raw tape on the thread. When screwing, use a wrench to clamp the hexagonal valve body screwed into one end of the pipe.
5. When installing the flange valve, pay attention to tighten the connecting bolts along the diagonal direction, and the force should be even when screwing to prevent the gasket from deviating or causing the valve body deformation and damage.
6. The valve shall be kept closed during installation. For threaded valves close to the wall, it is often necessary to remove the valve stem, disc and handwheel before screwing. During disassembly, the valve shall be disassembled after turning the handwheel to keep it open.
WUXI KVC-VALVE