Valve check before installation

Carefully check whether the valve model and specifications meet the requirements of the drawings.

Check if the stem and flap are open, and if they are stuck or skewed.

Check for damage to the valve and whether the threads of the threaded valve are correct and intact.

Check the tightness of the valve seat and the valve body, the connection between the valve disc and the valve seat, the valve cover and the valve body, and the valve stem and the valve disc.

Check that the valve gasket, packing, and fasteners (bolts) are suitable for the nature of the working media.

Older or longer-lasting pressure reducing valves should be dismantled, and dust, sand and other debris should be cleaned with water.

Remove the vent cover and check the seal. The disc must be closed tightly.

Low-, medium-, and high-pressure valves are to be subjected to strength tests and tightness tests. The alloy steel valves should also be subjected to spectral analysis of the shells one by one and the materials must be reviewed.

Valve pressure test

Valve strength test

The strength test of the valve is tested in the open state of the valve and the leakage of the outer surface of the valve is checked. For valves with PN ≤ 32MPa, the test pressure is 1.5 times the nominal pressure, the test time is not less than 5 minutes, and no leakage is found at the housing and packing gland.

Valve tightness test

When the valve is fully closed, check whether the sealing surface of the valve is leaking. The test pressure, except for the butterfly valve, check valve, bottom valve, and throttle valve, should normally be measured with nominal pressure. When working pressure, it can also be tested with 1.25 times the working pressure, so that the sealing surface of the valve flap is acceptable.

General requirements for valve installation

The position where the valve is installed should not hinder the operation, disassembly and maintenance of the equipment, pipes and the valve body itself, and at the same time, the aesthetic appearance of the assembly should be taken into account.

The valve on the horizontal pipe is installed with the stem facing upwards, or inclined at a certain angle. It cannot be installed with the handwheel down. Valves, stems, and handwheels on high-altitude pipelines can be installed horizontally, and the chain can be opened and closed remotely using the chain at the bottom.

Symmetrical arrangement, neat and beautiful; the valve on the riser, under the premise of the process allows, the valve hand wheel to the chest height is most suitable for operation, generally from the ground one to two meters is appropriate, and the stem must follow the operation The direction of installation.

The valve on the side-by-side riser should have the same centerline elevation and the net distance between the handwheels should not be less than 100mm; the valves on the side-by-side horizontal pipeline should be staggered to reduce the distance between the pipes.

When installing heavier valves on pumps, heat exchangers, etc., a valve bracket shall be provided. When the valve is operated frequently and installed on a valve more than 1.8 m away from the operating surface, a fixed operating platform shall be provided.

The valve body is marked with an arrow, and the direction of the arrow is the flow direction of the medium. When installing the valve, care should be taken to point the arrow at the same direction as the flow of media in the pipe.

When installing the flange valve, ensure that the two flange faces are parallel and concentric and do not use double gaskets.

When installing threaded valves, one threaded valve shall be fitted with a live connection for ease of disassembly. The setting of live connection should take into account the convenience of overhauling, which is usually the flow of water through the valve after the live connection.

Valve installation precautions

The body material of the valve is mostly made of cast iron and is brittle, so it must not be struck by heavy objects.

When transporting the valve, it is not allowed to throw; when hoisting or lifting the valve, the rope should be attached to the valve body, and it is strictly prohibited to pry on the hand wheel, valve stem and flange bolt hole.

3 The valve should be installed in the most convenient place for operation, maintenance and inspection. It is strictly prohibited to bury it underground. Directly buried valves and valves in the trenches shall be provided with inspection wells to facilitate opening and closing of the valves.

Make sure that the thread is intact, and wrap the hemp on the thread, apply lead oil, or wrap the PTFE raw tape. When turning the buckle, use a wrench to lock the hex body screwed into one end of the tube.

When installing the flange valve, pay attention to tighten the connecting bolt along the diagonal direction, and use even force when twisting to prevent the gasket from deviating or causing deformation and damage of the valve body.

The valve should remain closed during installation. For threaded valves close to the wall, it is often necessary to remove the valve stem and handwheel during installation in order to turn. When disassembling, remove the handwheel after turning the valve open.