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Some brief knowledge you must know to install the valve
Sep 17, 2018

Many valves have directionality, such as shut-off valves, throttle valves, pressure reducing valves, check valves, etc., if installed reversed, it will affect the effect and life (such as throttle), or not at all (such as Pressure reducing valve), even causing danger (such as check valves). Generally, the valve has a direction mark on the valve body; if it is not, it should be correctly identified according to the working principle of the valve. The valve chamber of the shut-off valve is asymmetrical to the left and right, and the fluid should be passed from bottom to top through the valve port, so that the fluid resistance is small (determined by the shape), the labor is turned on (because the medium pressure is upward), and the medium is not pressed after the closing, which is convenient for maintenance. This is why the stop valve can't be reversed. Other valves also have their own characteristics.
The valve installation position must be convenient for operation: even if the installation is temporarily difficult, it is necessary for the operator's long-term work. It is best to have the valve handwheel and the chest (usually 1.2 meters away from the operating floor), so that opening and closing the valve is more labor-saving. The floor valve hand wheel should be facing upwards, do not tilt, so as to avoid awkward operation. The valve against the wall machine should also leave room for the operator to stand. It is necessary to avoid the operation of the sky, especially acid and alkali, toxic media, etc., otherwise it is very unsafe. Do not flip the gate (ie, the handwheel is down), otherwise the medium will remain in the bonnet space for a long time, which will easily corrode the valve stem and is contraindicated for certain process requirements. It is inconvenient to replace the packing at the same time Open the gate valve, do not install it in the ground, otherwise the exposed valve stem will be corroded due to moisture. Lifting check valve, the valve flap should be vertical when installing, so that the lifting is flexible. Swing-type check valve, to ensure the level of its pin when installing, so that the swing is flexible. The pressure relief valve should be installed upright on a horizontal pipe and should not be tilted in all directions.
(2) Construction operations
Care must be taken during installation and construction. Do not hit the valve made of brittle material.
Before installation, the valve should be inspected, check the specifications and models for damage, especially for the valve stem. Also turn a few times to see if it is skewed, because it is most likely to hit the valve stem during transportation. Also remove debris from the valve.
When the valve is lifted, the rope should not be attached to the handwheel or the valve stem to avoid damage to these parts and should be attached to the flange.
Always clean the piping connected to the valve. Compressed air can be used to blow off iron oxide chips, mud sand, welding slag and other debris. These debris not only easily scratch the sealing surface of the valve, but also large particles (such as welding slag) can also block the small valve and make it invalid. When installing the screw valve, the sealing packing (line hemp aluminum oil or Teflon raw material tape) should be wrapped on the pipe thread and not in the valve to avoid the valve memory and affect the circulation of the medium.
When installing the flange valve, pay attention to tightening the bolt symmetrically and evenly. The valve flange and the pipe flange must be parallel and the clearance is reasonable to avoid excessive pressure or even cracking of the valve. Pay particular attention to brittle materials and valves that are not strong enough. The valve to be welded to the pipe shall be spot welded first, then the closing member shall be fully opened and then welded.
(3) Protective measures
Some valves must also have external protection, which is insulation and cold preservation. Hot steam lines are sometimes added to the insulation layer. What kind of valve should be insulated or kept cold, depending on the production requirements.
In principle, if the medium in the valve reduces the temperature too much, it will affect the production efficiency or freeze the valve, so it needs to be insulated or even mixed with heat; if the valve is exposed, it is unfavorable to production or cause frosting and other undesirable phenomena, it needs to keep cold. Insulation materials are asbestos, slag cotton, glass wool, perlite, diatomaceous earth, vermiculite, etc.; cold insulation materials are cork, perlite, foam, plastic and so on.
(4) Bypass and instrument
Some valves, in addition to the necessary protective facilities, also have bypass and instrumentation. A bypass is installed. Easy to repair the trap. Other valves are also installed with bypass. Whether to install the bypass depends on the condition of the valve, the importance and the requirements of the production.
(5) Filler replacement
Inventory valves, some fillers are not good, and some do not match the use of media, which requires replacement of fillers.
Valve manufacturers can't consider using different mediums of thousands of units. The packings are always filled with ordinary packing, but when used, the packing must be adapted to the medium.
When replacing the packing, press it in a circle. The seam is preferably 45 degrees per turn, and the circle and the ring are opened 180 degrees. The height of the packing should consider the room for the gland to continue to be compacted. At present, the packing chamber should be pressed to the appropriate depth of the packing chamber. This depth can generally be 10-20% of the total depth of the packing chamber. For valves with high requirements, the joint angle is 30 degrees. The seam between the circle and the circle is staggered by 120 degrees. In addition to the above fillers, rubber O-rings can be used according to the specific conditions (natural rubber is resistant to weak alkali below 60 degrees Celsius, nitrile rubber is resistant to oil crystals below 80 degrees Celsius, and fluororubber is resistant to various corrosive media below 150 degrees Celsius) Formed packings such as laminated PTFE rings (resistant to strong corrosive media below 200 degrees Celsius), nylon bowl rings (resistant to 120 degrees Celsius, ammonia, alkali). On the outside of the ordinary asbestos packing, a layer of Teflon raw material tape is wrapped to improve the sealing effect and reduce the electrochemical corrosion of the valve stem.
When pressing the seasoning, turn the valve stem at the same time to keep the circumference evenly and prevent it from being too dead. To tighten the gland, apply even force and not tilt.

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