Five key points for valve installation

1 Direction and position
Many valves are directional
For example, stop valve, throttle valve, pressure reducing valve, Check Valve, etc., if installed upside down, will affect the service effect and life (such as throttle valve), or will not work at all (such as pressure reducing valve), or even cause danger (such as check valve). For general valves, there are direction signs on the valve body. If not, it should be correctly identified according to the working principle of the valve.
The valve chamber of the stop valve is asymmetric from left to right. The fluid should pass through the valve port from bottom to top, so that the fluid resistance is small (determined by the shape), the opening is labor-saving (due to the upward pressure of the medium), and the medium does not press the packing after closing, which is convenient for maintenance, which is why the stop valve cannot be reversed. Other valves also have their own characteristics.
The installation position of the valve must be convenient for operation
Even if the installation is temporarily difficult, the long-term work of the operators should be considered. It is better to align the valve handwheel with the chest (generally 1.2 meters from the operating floor), so that it is easier to open and close the valve. The hand wheel of the floor valve should be upward and not inclined to avoid awkward operation. The valve of the wall machine against the equipment should also leave room for operators to stand.
It is necessary to avoid operations in the sky, especially acid and alkali, toxic media, etc., otherwise it is very unsafe.
Do not install the gate upside down (that is, the handwheel is downward), otherwise the medium will be left in the bonnet space for a long time, which is easy to corrode the valve stem, and is forbidden by some process requirements. It is extremely inconvenient to replace the packing at the same time. The rising stem Gate Valve shall not be installed underground, otherwise the exposed valve rod will be corroded due to humidity.
When installing the lift check valve, ensure that the valve disc is vertical, so as to lift flexibly. When installing the swing check valve, ensure that its pin shaft is horizontal, so that the swing can be flexible. The pressure reducing valve should be installed vertically on the horizontal pipe, and should not tilt in all directions.
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2 Construction operation
Care must be taken in installation and construction to avoid hitting valves made of brittle materials.
Before installation
Carefully check whether the model and specification of all valves meet the design requirements.
(According to the valve model and factory instructions, check whether they can be applied under the required conditions, and conduct hydraulic or pneumatic test if necessary.)
In addition, check whether the packing is intact, whether the gland bolts have sufficient adjustment allowance, and whether the valve rod and valve disc are flexible, and whether they are stuck or skewed.
(The sealing surface of the valve disc must be closed tightly, and the thread quality of the threaded valve should be checked. The unqualified valve cannot be installed, and should be separately stacked or marked.)
Clear the sundries in the valve.
setup script
When lifting the valve, the rope should not be tied to the handwheel or valve rod to avoid damaging these parts. It should be tied to the flange.
The pipeline connected to the valve must be cleaned.
Compressed air can be used to blow away iron oxide, sand, welding slag and other sundries. These sundries are not only easy to scratch the sealing surface of the valve, but also can block the small valve and make it invalid.
When installing the screw valve, the sealing packing (hemp plus aluminum oil or polytetrafluoroethylene raw material belt) should be wrapped on the pipe thread, and should not be put into the valve, so as to avoid accumulation in the valve and affect the flow of media.
When installing the flange valve, pay attention to tighten the bolts symmetrically and evenly. The valve flange and pipe flange must be parallel with reasonable clearance to avoid excessive pressure or even cracking of the valve. Special attention shall be paid to brittle materials and valves with low strength. For valves that must be welded with pipes, spot welding shall be carried out first, then the closing parts shall be fully opened, and then welded.
3 Protective measures
Some valves also need external protection, which is thermal insulation and cold insulation. Hot steam pipelines are sometimes added in the insulation layer. What kind of valve should be kept warm or cold depends on the production requirements.
In principle, if the temperature of the medium in the valve decreases too much, it will affect the production efficiency or freeze the valve, so it needs to be insulated, or even heated; When the valve is exposed, which is harmful to production or causes frost and other undesirable phenomena, cold insulation is required. Thermal insulation materials include asbestos, slag wool, glass wool, perlite, diatomite, vermiculite, etc; Cold insulation materials include cork, perlite, foam, plastic, etc.
4 Bypass and instrument
In addition to necessary protection facilities, some valves also need bypass and instruments. Bypass is installed. It is convenient for maintenance of drain valve. Other valves are also equipped with bypass. Whether to install bypass depends on the condition, importance and production requirements of the valve.
5 Packing replacement
For the valves in stock, some of the packing is not easy to use, and some are not consistent with the medium used, so it is necessary to replace the packing.
The valve manufacturer cannot consider the use of different media with thousands of doors and thousands of categories. The stuffing box is always filled with ordinary packing, but the packing must be adapted to the media when used.
When replacing the packing, press it in circle by circle. The joint of each circle should be 45 degrees, and the circle should be 180 degrees apart. The packing height should consider the space for the gland to continue to compress. At present, the lower part of the gland should be pressed to the proper depth of the packing chamber, which 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 joints between the rings are staggered by 120 degrees.
In addition to the above fillers, rubber O-ring (natural rubber resistant to weak alkali below 60 ℃, NBR resistant to oil crystals below 80 ℃, and fluororubber resistant to various corrosive media below 150 ℃), three-piece laminated PTFE ring (resistant to strong corrosive media below 200 ℃), nylon bowl ring (resistant to ammonia and alkali below 120 ℃) and other shaped fillers can also be used according to specific conditions.
A layer of polytetrafluoroethylene raw material belt is wrapped outside the ordinary asbestos packing, which can improve the sealing effect and reduce the electrochemical corrosion of the valve rod. When pressing the seasoning, the valve rod should be rotated at the same time to maintain the uniformity around and prevent it from being too tight. The gland should be tightened with even force and should not be tilted.