1 direction and position
Many valves have directivity
For example, cut-off valves, throttle valves, pressure reducing valves, check valves, etc. If installed anti-flip, it will affect the use of effects and life expectancy (such as throttle), or does not work (such as pressure reducing valve) Danger (such as check valve). General valve, the direction of the valve body signs. In case of no, should be based on the working principle of the valve, the correct identification.
Valve valve cavity around the valve is asymmetric, the fluid to pass from the bottom up through the valve port, so the fluid resistance is small (determined by the shape), open the labor-saving (due to media pressure upward) This is why the stop valve can not be anti-anti-truth. Other valves also have their own characteristics.
Valve installation location, must be easy to operate
Even if the temporary installation of some difficulties, but also long-term operator for the sake of work. The best valve hand wheel and take the chest (generally from the operating floor 1.2 m), so that more open and close the valve. Landing valve hand wheel to be up, do not tilt, so as not to operate awkward. Wall by the machine valve equipment, but also set aside room for operators to stand. To avoid the sky operation, especially acid, toxic media, etc., otherwise it is not safe.
Do not flip the gate (that is, the handwheel down), otherwise it will leave the media long in the bonnet space, easy to corrode the valve stem, and for some of the requirements of the taboo. At the same time changing the packing is very inconvenient. Ming pole valve, do not install in the ground, or corrosion due to moisture exposed stem. Lift check valve, the installation of the valve to ensure that vertical, in order to lift flexible. Swing check valve, the installation of the pin to ensure that the level, so spin Kai flexible. Relief valve to be installed upright in the horizontal pipe, do not tilt in all directions.
2 construction operations
Installation must be careful not to hit the valve made of brittle materials.
Before installation
Should carefully check all valve models and specifications are in line with design requirements. (Depending on the type of valve and the manufacturer's instructions, check if they can be used under the required conditions and, if necessary, make hydraulic or pneumatic tests.) In addition, check that the packing is intact and that the gland bolts have adequate adjustment allowances, And to check whether the valve stem and valve discourse, whether stuck and skew phenomenon.
(The sealing face of the valve disc must be closed tightly, and the quality of the thread should be checked for threaded connections.) The unqualified valve can not be installed and should be stacked or marked separately.) Clear debris in the valve.
Installation process
When lifting the valve, the rope should not be tied to the handwheel or the valve stem, so as to avoid damaging the parts and should be fastened to the flange.
The valve connected to the pipeline, be sure to clean.
Available compressed air blown iron oxide dust, mud, welding slag and other debris. These debris, not only easy to seal the sealing surface of the valve, including large particles of debris (such as welding slag), but also blocked small valves, so that failure.
Install the screw valve, seal packing (line Ma plus aluminum or Teflon raw material band), wrapped in the pipe thread, do not get the valve, so as to prevent the accumulation of the valve, affecting the flow of media.
When installing the flange valve, pay attention to symmetrically and evenly tighten the bolt. Valve flange and pipe flange must be parallel, the gap is reasonable, so as to avoid excessive pressure on the valve, and even cracking. Pay special attention to brittle materials and valves with low strength. To be welded with the pipe valve, the first spot welding, and then close the full-open, and then welded to death.
3 protective measures
Some valves must also have external protection, which is insulation and cold. Insulation sometimes add hot steam pipelines sometimes. What kind of valve should be insulated or cold, according to production requirements.
In principle, where the valve medium to reduce the temperature is too much, will affect the production efficiency or freeze the valve, you need insulation, or even mixed heat; where the valve exposed, adverse or cause frosting and other undesirable phenomena, you need to keep cold. Insulation materials are asbestos, slag cotton, glass wool, perlite, diatomaceous earth, vermiculite, etc .; cold materials are cork, perlite, foam, plastic and so on.
4 Bypass and meter
Some valves, in addition to the necessary protection facilities, but also by-pass and instrumentation. Bypass installed. Easy trap maintenance. Other valves, also installed bypass. Whether to install the bypass, depending on the valve status, importance and production requirements may be.
5 filler replacement
Inventory valve, some packing is not good, and some do not match with the use of media, which need to change stuffing.
Valve manufacturers can not consider the use of thousands of different units of media, stuffing box is always filled with ordinary packing, but when used, you must make the filler in the media to adapt.
In the replacement of packing, to be lap circle into. Each lap to 45 degrees is appropriate, laps and laps open 180 degrees. The height of the packing should consider the room where the gland will continue to be compressed. At this moment, the lower part of the gland should be pressed with appropriate depth of the packing room, which can be 10-20% of the total depth of the packing room. For demanding valves, the joint angle is 30 degrees. Seams between circles staggered by 120 degrees.
In addition to the above fillers, but also according to the specific circumstances, the use of rubber O-ring (natural rubber resistant to weak base below 60 degrees Celsius, Dingqing rubber-resistant oil below 80 degrees Celsius, fluorocarbon rubber resistant to 150 degrees Celsius below a variety of corrosive media) Stacked PTFE ring (resistant to 200 degrees Celsius below the corrosive medium) nylon bowl (resistant to 120 degrees Celsius ammonia, alkali) and other forming filler. Outside the ordinary asbestos packing, a layer of Teflon tape, can improve the sealing effect, reduce the valve stem electrochemical corrosion. In pressing the seasoning, the stem should be rotated at the same time, in order to maintain a uniform around, and to prevent too dead, tighten the gland to force evenly, can not be tilted.
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