The gate should not be inverted (that is, the handwheel is down), otherwise the medium will be retained in the cover space for a long time, easy to corrode the stem, and for some process requirements taboo. It is extremely inconvenient to replace packing at the same time. Open STEM GATE VALVES, DO NOT INSTALL underground, otherwise due to damp corrosion of the exposed stem. Lift check valve, installation to ensure that the valve disc vertical, so that the lift flexible. Swing check valve, when installed to ensure that the pin level, in order to swing flexible. The pressure reducing valve shall be installed upright on the horizontal pipe, and shall not tilt in any direction.
Installation and construction must be careful, do not hit the valve made of brittle materials.
Before the installation
All valve types and specifications shall be carefully checked for compliance with design requirements.
(CHECK whether they CAN BE USED IN THE REQUIRED conditions according to the valve model and factory instructions, and perform water or air pressure tests if necessary.)
In addition, it should also be checked whether the packing is intact, whether the gland bolt has enough adjustment allowance, and to check whether the stem and disc are sound, whether there is stuck and skew phenomenon.
The sealing surface of valve disc must be closed tightly, and the quality of thread should be checked for threaded valves. Unqualified valves shall NOT be INSTALLED and shall be separately stacked or marked.
Remove debris from valve.
The installation process
When LIFTING THE VALVE, THE ROPE SHOULD NOT BE TIED TO THE HANDWHEEL OR STEM TO AVOID DAMAGE TO THESE PARTS. It SHOULD BE TIED TO THE flange.
The line to which the valve is connected must be cleaned.
Compressed air can be used to blow iron oxide filings, sand, welding slag and other sundries. These debris, not only easy to scratch the sealing surface of the valve, the large particles of debris (such as welding slag), but also can block the small valve, so that its failure.
When INSTALLING THE SCREW VALVE, THE SEALING PACKING (WIRE AND aluminum oil OR PTFE RAW material belt) should be wrapped on the pipe thread, do not get into the valve, so as to avoid the valve memory volume, affect the medium flow.
When installing flange valves, pay attention to tighten the bolts symmetrically and evenly. The valve flange and the pipe flange must be parallel, the clearance is reasonable, lest the valve produces excessive pressure, even crack. For brittle materials and not high strength of the valve, special attention should be paid. The valve to be welded with the pipe shall be spot welded first, then the closed part shall be fully opened, and then welded dead.
Some valves must also have external protection, which is heat preservation and cold retention. The insulation layer is sometimes mixed with hot steam lines. What kind of valve should be heat or cold, according to the production requirements.
In principle, where the valve medium to reduce the temperature is too much, will affect the production efficiency or frozen valve, you need to keep warm, even mix heat; Where the valve is bare, adverse to production or cause frost and other adverse phenomena, you need to keep cold. Insulation materials are asbestos, slag wool, glass wool, perlite, diatomite, vermiculite, etc.; The cooling materials are cork, perlite, foam, plastic and so on.
4.Bypass and meter
Some valves, in addition to the necessary protection facilities, also have bypass and instrumentation. A bypass is installed. Easy to repair the trap. Other valves, also installed bypass. Bypass installation depends on valve condition, importance, and production requirements.
Stock valve, some packing has not been good, and some do not conform to the use of media, which needs to replace the packing.
Valve factory can not consider the use of thousands of different types of media, packing box is always filled with ordinary root, but when used, must let the packing in the medium to adapt.
When replacing packing, press in round by round. Each ring seam to 45 degrees is appropriate, ring and ring open 180 degrees. The packing height should consider the leeway for the gland to continue pressing, and now it is necessary to let the lower part of the gland press the packing chamber to an appropriate depth, which can generally be 10-20% of the total depth of the packing chamber. For demanding valves, the joint Angle is 30 degrees. The seam between the ring and the ring is staggered 120 degrees.
In addition to the packing, but also according to the specific situation, the use of rubber O-ring (natural rubber resistant to 60 degrees Celsius weak alkali, butadiene rubber resistant to 80 degrees Celsius oil crystal, Fluorine rubber resistant to a variety of corrosive media below 150 degrees Celsius) three stacked polytetrafluoron ring (resistant to strong corrosive media below 200 degrees Celsius) nylon bowl ring (resistant to 120 degrees Celsius ammonia, alkali) and other forming filler. A layer of TEflon raw material tape can improve the sealing effect and reduce the electrochemical corrosion of the valve stem. When pressing the seasoning, turn the stem at the same time to keep all around evenly, and prevent too dead, tighten the gland to force evenly, can not tilt.