Precautions for Valve Installation

What precautions should be taken during valve installation? The relevant specifications and key points are explained in detail as follows:
1. Clean the inner cavity and sealing surface of the valve before installation. Tighten the connecting bolts evenly and check whether the packing is fully compressed.
2. Install the valve in a fully closed state.
3. Large-size gate valves and pneumatic regulating valves shall be installed vertically to avoid deviation of the valve core caused by self-weight, which may lead to medium leakage.
4. Follow standardized and formal installation procedures throughout the construction process.
5. Install the valve at the permitted working position, and ensure convenient maintenance and operation.

6. For globe valves, the medium flow direction shall be consistent with the arrow marked on the valve body. For valves that are rarely opened and closed and require strict zero leakage in the closed state, 

reverse installation is allowed, so that the medium pressure can assist tight closing.

7. Keep the valve slightly open when tightening the compression screws to prevent damaging the top sealing surface of the valve.
8. Conduct opening and closing tests on low-temperature valves in a cold state before positioning, to ensure flexible operation without jamming.
9. For liquid service valves, install the valve stem at a 10° inclination to the horizontal plane, so as to prevent liquid leakage along the valve stem.
10. For large air separation towers, pre-tighten all connecting valve flanges in a cold state after bare cooling, to avoid leakage at low temperature despite no leakage at room temperature.
11. It is strictly prohibited to climb or stand on the valve stem as a scaffold during installation.
12. After all valves are installed in place, conduct opening and closing tests again. The installation is qualified if the valves operate flexibly without jamming.
13. Position and fix valves before pipeline installation. Keep the pipeline naturally aligned without forced bending, so as to avoid residual pre-stress.
14. Non-metallic valves are usually hard and brittle with low structural strength. Avoid excessive or sudden force during opening and closing, and prevent collision and impact damage.
15. Avoid collision, scratching and mechanical damage during valve handling and installation.
16. For newly installed valves, do not compress the packing excessively; adjust it to a leakage-free state. Excessive compression will cause overpressure on the valve stem, accelerate wear and result in difficult operation.
17. Verify that all valves comply with design requirements and relevant industry standards before installation.
18. Thoroughly clean the interior of pipelines before valve installation to remove iron filings and other impurities, preventing foreign matter from sticking to the valve sealing seat.
19. High-temperature valves are installed at room temperature. After operation and temperature rise, the bolts will expand thermally and produce gaps. Secondary tightening is required to prevent medium leakage.
20. Confirm that the medium flow direction, installation mode and handwheel position of the valve meet specification requirements before installation.