When installing the gate valve, you must pay attention to:
1. Rising stem valves cannot be laid directly underground.
To prevent corrosion of the valve stem, it can only be installed in a covered trench. The valve should be installed in a location that is convenient for operation, inspection, disassembly, maintenance and operation.
2. When transporting the valve, it is not allowed to throw it away to avoid damage and deformation.
When stacking, carbon steel valves should be separated from stainless steel valves and non-ferrous metal valves. When lifting the valve, the wire rope should be tied to the connecting flange between the valve body and the valve cover. Do not tie it to the handwheel or valve stem to prevent damage to the valve stem and handwheel.
The installation height should be convenient for operation and maintenance. Generally, the distance between the valve operating handle and the ground is 1-1.2m. For valves with a large number of operations, when they must be installed more than 1.8m away from the operating surface, a fixed operating platform should be installed. When they must be installed above or below the operating surface (public account: Pump Steward), an extension rod or an extension rod should be installed. The valve stem is installed horizontally, and a handwheel with a transmission device or a remote operating device is installed.
The angle between the axis of the valve transmission device should not be greater than 30°, and its joints should be flexible to rotate, easy to use during operation, and have accurate instructions. For valves with thermal displacement, the transmission device should have compensation measures.
4. For horizontal pipelines, it is best to install the valve vertically upward or install the valve stem within the upper semicircle, but the valve stem must not be installed downward.
Valve stems and handwheels on vertical pipelines must be installed along the direction of the operating circuit. When possible, valves should be installed as centrally as possible to facilitate operation. Valves on pipelines in the tower area that are more than 4m above the ground should not be set outside the platform to facilitate installation and operation.
If a stop valve is installed, the medium should flow from the bottom of the cabinet plate to the top, commonly known as low in and high out.
When installing a check valve, special attention must be paid to the flow direction of the medium to ensure that the valve disc can open automatically. In important situations, an arrow must be clearly marked on the valve body to indicate the direction of the medium flow.
For swing check valves, ensure that the rotating pivot of the insert plate is installed in a horizontal position. For lift check valves, ensure that the center line of the valve disc is perpendicular to the horizontal plane.
6. For valves with special requirements, be familiar with the installation requirements.
For example, when installing lever-type safety valves and pressure reducing valves, the centerline of the valve disc and the horizontal plane must be perpendicular to each other. If tilt is found, correction must be made.
7.Install the union.
When installing a threaded valve on a pipeline, a union must be installed near the valve to facilitate disassembly and assembly.
8. A cut-off valve should be installed when the auxiliary system pipeline enters the workshop.
When the workshop is shut down for maintenance, it can be cut off from the main pipeline. The installation height of these valves is generally high and should be arranged together as much as possible to facilitate the installation of a fixed operating platform.
9. Install flange-connected valves.
Make sure that the two flange end faces connected to it are parallel and coaxial with the valve flange. Especially when installing valves made of brittle materials such as cast iron, valve damage caused by incorrect installation positions and uneven stress should be avoided. When tightening flange bolts, use a symmetrical or crisscross method, and tighten gradually in several intervals.
10. Before installing high-pressure valves, the product certificate and test records must be reviewed.
High-pressure valves are mostly angle valves. When used, two are often connected in series. The starting force is large when opening. A valve frame must be installed to support the valve and reduce starting stress. The appropriate installation height is 0.6-1.2m.
11. The pipe joints on pumps, heat exchangers, towers and vessels should not bear the weight of valves and pipes. Valves with nominal diameter dn>80mm should be equipped with brackets.
12. The lining, spraying and non-metallic door itself has a large mass and low strength. In addition to considering the process requirements, it should be arranged as centrally as possible to facilitate the design of the valve frame.
Even a single valve should be fixed to the valve frame. When installing heavy valves on horizontal pipes, consider installing brackets on both sides of the valve.
13. When installing valves with threaded connections, ensure that the threads are intact.
The packing should be selected according to the working conditions, and the position of the valve stem when tightened in place should meet the installation requirements. When tightening, a wrench must be used to tighten the hexagonal body of the valve at one end of the pipe to ensure that the valve body is not twisted, deformed, or damaged. Valves with flanged or threaded connections should be installed in the closed state.
The valve should not be closed during welding to prevent overheating and deformation of the sealing surface. If the sealing material is not resistant to high temperatures, the sealing material must be removed before welding to prevent the high temperature of welding from damaging the sealing material.
15. For valves on side-by-side pipelines, the net distance between the handwheels shall not be less than 100mm. In order to reduce the distance between pipelines, it is best to stagger the valves arranged side by side.
16. Before positioning the cryogenic valve, the opening and closing test should be carried out in a cold state as much as possible, and it is required to be flexible and free of jamming.
17. The connection of the safety valve should have an elbow (or accessories such as tee).
Avoid direct impact of fluid on the valve; in addition, ensure that the safety valve does not frost during operation to avoid failure during operation.
18. It is strictly prohibited to use the valve stem as a scaffolding to climb when installing the valve.
19. High temperature valves above 200℃.
Since the valve is at normal temperature when installed, and after normal use, the temperature rises, the valve bolts expand due to heat, and the gap increases, so they must be tightened again, which is called “heat tightening”. The operator should pay attention to this task, otherwise valve leakage will easily occur. event.
20. In cold winter, if the water valve is closed for a long time, the accumulated water behind the valve should be removed.
After the steam valve stops steam, the condensed water must also be removed. The bottom of the valve is like a drain switch, which can be opened to drain water.
21. Some non-metallic valves are hard and brittle, and some have low strength. When operating, the opening and closing force should not be too large, especially not with force. Also pay attention to avoid collision with objects.
22. When installing the stop valve, the flow direction should be consistent with the arrow marked on the valve body (it cannot be installed backwards).
When the valve is closed, pressure is added to the cone on the top of the valve, and the packing is not loaded. However, for valves that do not open and close frequently but need to be strictly guaranteed not to leak when closed (such as heating valves), they can be consciously reversed as needed to make them tightly closed with the help of medium pressure.
23. Large-sized gate valves (DN200-500MM) and pneumatic regulating valves should be installed vertically.
This prevents the valve core from leaning to one side due to its heavy weight, which increases mechanical wear between the valve core and the bushing and causes leakage.
24. When tightening the compression screw, the valve should be slightly open to avoid damaging the valve top sealing surface.
26. When using a new valve, the packing should not be pressed too tightly to ensure that it does not leak, so as to avoid excessive pressure on the valve stem, accelerated wear, and difficulty in opening and closing.
