Many valves have directional, such as cut-off valve, throttle valve, valve, check valve, etc., if the reverse, will affect the use of the effect and life (such as throttle valve), or simply do not work (such as relief valve), or even cause danger (such as check valve). General valve, the valve body on the direction of signs; if not, should be based on valve working principle, correct identification. The valve cavity around the cut-off valve is asymmetrical, fluid to let it from the bottom through the valve mouth, so that the fluid resistance is small (determined by the shape), open labor (due to the medium pressure upward), after the media is not pressure filler, easy to overhaul, this is the cut-off valve why not ann the truth.
Other valves also have their own characteristics.
Then, valve installation should pay attention to what problems?
Installation location Valve installation location, must be easy to operate: even if the installation of temporary difficulties, but also for the operator's long-term work for the sake of. The best valve handwheel and chest Chinzi (general from the operation floor 1.2 meters), in this way, opening and closing valves are more jingxiang. Landing valve handwheel to face up, do not tilt to avoid awkward operation. Depending on the equipment of the wall machine valve, but also to leave the operator standing room. To avoid the operation of the Yang, especially acid-base, toxic media, etc., otherwise very unsafe. The gate does not flip (that is, handwheel downward), otherwise it will keep the medium for a long time in the cover space, easy to corrode stem, and for some technical requirements are taboo. At the same time the replacement of filler is extremely inconvenient. Clear STEM gate valve, do not install underground, otherwise corrosion exposed stem due to damp. Lift check valve, when installed to ensure that its disc vertical, in order to lift flexible. Swing check Valve, when installed to ensure that the pin shaft level, so that the rotation flexible.
The pressure relief valve should be installed upright on the horizontal pipe, not inclined in all directions.
Construction work
Installation construction must be careful not to impact the production of brittle materials valve. Before installation, the valve should be checked, check the specification model, identify damage, especially for stem. Also want to rotate a few, see whether skew, because the transport process, the most easily hit the crooked stem.
Also remove the debris in the valve.
When the valve is hoisted, the rope should not be tied to the handwheel or stem to avoid damaging these parts and should be fastened to the flange. For valves connected to the pipeline, must be cleaned. The compressed air can be used to blow up iron oxide crumbs, mud sand, solder slag and other sundries. These sundries, not only easy to scratch the valve sealing surface, which large particles (such as slag), but also can block small valves, so that its failure.
Install the screw valve, should be sealed filler (wire hemp plus aluminum oil or PTFE raw material belt), wrapped in pipe thread, do not get into the valve, lest the valve memory product, affecting the media flow. When installing the flange valve, pay attention to symmetrical and evenly tighten the bolt. The valve flange and the pipe flange must be parallel, the clearance is reasonable, lest the valve produces the excessive pressure, even cracks. For brittle materials and low strength valves, pay particular attention to.
The valve must be welded with the pipe, first spot welding, and then the closing part is fully open and then welded to death.
Protection measures Some valves also need to have external protection, which is insulation and cooling. Hot steam piping is sometimes added to the insulation layer.
What kind of valve should be warm or cold, according to production requirements. Principle that, where the medium temperature of the valve is too high, will affect the production efficiency or freeze the bad valve, you need to heat preservation, or even mix heat; where the valve is bare, adverse to production or cause frost and other undesirable phenomena, it is necessary to cool.
Insulation materials have asbestos, slag cotton, glass wool, perlite, diatomite, vermiculite and so on, cooling materials have cork, perlite, foam, plastic and so on.
Bypass meter Some valves, in addition to the necessary protection facilities, but also bypass and instrumentation. The bypass is installed. Easy to trap and overhaul. Other valves are also fitted with bypass.
Whether to install bypass, depends on valve status, importance and production requirements.
Filler replacement
Inventory valve, some fillers have been invalidated, and some of the use of media does not match, which requires replacement filler.
Valve factory can not consider the use of units thousand door drifting different media, filling letter is always filled with ordinary packing, but when used, must let the filler in the medium to adapt. In the replacement of fillers, to a circle of the press into the enclosure. Each lap seam to 45 degrees is appropriate, the circle and ring open 180 degrees. Filling height to consider the gland to continue to tighten the room, and now let the gland lower pressure filler chamber appropriate depth, this depth can generally be filled with the total depth of the 10-20%. For valves with high requirements, the seam angle is 30 degrees. The seam between the circle and the circle is staggered 120 degrees. In addition to the above filler, can also be based on the specific situation, the use of rubber O-ring (natural rubber resistance to 60 degrees Celsius below the weak base, NBR rubber resistance to 80 degrees Celsius below the oil crystal, fluorine rubber resistance to 150 degrees Celsius below a variety of corrosive media) three pieces of laminated PTFE ring (resistant to 200 degrees Celsius under strong corrosive Resistant to 120 degrees Celsius ammonia, alkali, such as forming filler. Outside the ordinary asbestos packing, a layer of PTFE raw material belt, can improve the sealing effect, reduce the valve stem of electrochemical corrosion.