The type of valve used, the type of specifications, the use of what kind of valve, should be based on the use of the valve, the media characteristics, the maximum working pressure, the maximum temperature and the media flow rate, flow or pipe diameter to choose.
Before installation, should carefully check all the valve models and specifications are in line with design requirements. Depending on the valve type and the factory instructions, check whether they can be applied under the required conditions and, if necessary, for hydraulic or pneumatic tests. In addition, should check whether the filler is intact, gland bolts are sufficient to adjust the margin, and to check the stem and valve plate is the case, with or without the phenomenon of stuck and skew. The valve plate sealing surface must be closed tightly, and for threaded connections the valve should be checked for thread quality. Unqualified valves can not be installed and should be stacked or marked separately.
Precautions should be made when installing the valve
The valve can not be buried directly to prevent the rust stem, can only be installed in a covered trench, the valve should be installed in the operation, inspection, disassembly, maintenance and easy operation of the location. Do not throw the valve when handling the valve, so as not to damage and deformation. When stacked, carbon steel valves should be separated from stainless steel valves and non-ferrous metal valves. When the valve is lifted, the wire rope should be tied to the connecting flange of the valve body and the bonnet, and should not be tied to the hand wheel or stem to prevent damage to the stem and hand wheel.
The installation position of the valve shall not interfere with the disassembly, repair and operation of the equipment, piping and valves themselves. Installation height should be easy to operate, maintenance, the general operation of the valve handle from the ground 1-1.2m appropriate. Operation of more valves, when the installation must be more than 1.8m away from the operating surface, should be set up a fixed operating platform, when must be installed above or below the operating surface, should be set to extend the stem or horizontal installation of the stem, and then Install a handwheel with a drive or a remote operating device. Valve drive shaft angle should not be greater than 30 °, the joints should be flexible rotation, easy to use when operating, indicating accurate. There are heat displacement of the valve, the transmission device should have compensation measures.
Horizontal piping should be the vertical valve up or the valve stem installed in the upper semicircle range, but not the stem down to install. The valve stem on the vertical pipe, the hand wheel must be installed along the direction of the operation tour line. When conditional, the valve should be installed as much as possible to facilitate operation. More than 4m above the ground tower pipeline on the pipeline, should not be set aside in the platform to facilitate the installation and operation.
For directional valves, the installation should be based on the pipeline flow to determine the direction of its installation. Such as the installation of cut-off valve, the media should be from the top of the plate below the flow, commonly known as low into the high. When installing the cock and gate valve, allow the media to flow out from either end. When installing the check valve, you must pay special attention to the flow of the media in order to ensure that the valve plate can automatically open the important occasion but also in the valve body marked arrows, indicating the flow direction of the media. For swivel check valves, ensure that the swivel pivot of the flap is mounted in a horizontal position. For lift check valves, ensure that the disc centerline is perpendicular to the horizontal plane.
For special requirements of the valve, to be familiar with the installation requirements. If the lever-type safety valve and pressure reducing valve are installed, the center line of the valve disc must be perpendicular to each other and must be corrected when it is found.
When installing a threaded connection valve on the pipe, be sure to install the union in the vicinity of the valve for disassembly.
Auxiliary system piping into the workshop should be set off the valve, when the workshop parking maintenance, with the total pipe cut off. The installation height of these valves is generally high and should be arranged as much as possible to provide a fixed operating platform.
Install the flange connected to the valve, to ensure that the two flange connected with the valve flange parallel and coaxial line. Especially the installation of cast iron and other materials more brittle valve, it should avoid the installation location is not correct and uneven force caused by damage to the valve. Tighten the flange bolts, should be used symmetrical or cross the method, gradually tightened several times.
Before installing the high pressure valve, must check the product certificate and test record. High-pressure valves are mostly angle valves, often used in series, open the start force, you must set the valve frame to support the valve and reduce the starting stress, the installation height of 0.6-1.2m is appropriate.
Pumps, heat exchangers, towers and containers on the tube interface should not bear the weight of the valve and pipe, nominal diameter dn> 80mm valve should be added bracket.
Lining, spraying and non-metallic materials to ask the door itself is of high quality, low strength, in addition to considering the process requirements, should be as centralized as possible to facilitate the design of the valve. Even a single valve should be fixed to the valve frame. When installing heavy duty valves on horizontal piping, consider installing brackets on both sides of the valve.
Install the threaded connection of the valve should ensure that the thread is complete, according to the working conditions of the choice of filler, tighten in place when the stem position should meet the installation requirements. Tighten, you must use a wrench to tighten the tube at one end of the valve hexagonal body to ensure that the valve body does not twist deformation and damage. Flange or threaded connection of the valve should be installed in the closed state.
Welding valve and pipe connection welding seam back welding should use argon welding welding, to ensure its internal smooth and smooth. When welding the valve should not be closed, to prevent the sealing surface overheating deformation. If the sealing material is not high temperature, before welding to remove the sealing material to prevent welding high temperature damage sealing material.
Side of the pipeline on the valve, the hand wheel between the net distance of not less than 100mm, in order to reduce the pipe spacing, side by side arrangement of the valve is best staggered layout.
Low-temperature valve in the positioning should be done before the cold state to do the opening and closing test, requiring a flexible card without shell phenomenon.
Safety valve connection should be elbow (or three links and the like), to avoid direct impact of the valve valve; also to ensure that the safety valve in the operation of the frost, so as to avoid work failure. It is forbidden to climb the stem when the valve is installed.
High temperature valve 200 ℃ above, because the valve is installed at room temperature, and normal use, the temperature increases, the valve bolts heated expansion, the gap increases, it must be tightened again, called "hot tight", the operator should pay attention to this work , Otherwise prone to valve leakage and other events. Winter cold, the water valve long-term closure, the valve should be excluded after the water. After the steam valve stop, but also to exclude condensate. The bottom of the valve is like a drain switch that can open it drain. Non-metallic valves, some hard and brittle, and some low strength, the operation, the opening and closing force can not be too big, in particular, can not make fierce. But also pay attention to the provision of objects away bumps.
The flow direction of the stop valve should be the same as the arrow on the valve body (can not be installed), so that the valve closed when the pressure applied to the top of the cone, and the filler from the load. But not often open and close and the need to strictly ensure that the closed state of the valve (such as heating valve), according to the needs of consciously anti-installed to the media pressure to make it closed. Large-size gate valve (DN200-500MM), pneumatic control valve should be installed properly, so as to avoid the larger self-weight valve and bias to increase the spool between the mechanical wear and tear, resulting in leakage. When tightening the compression screw, the valve should be in the open state, so as not to crush the top seal surface. All the valves in place, should be made again and closed, flexible and non-stuck for qualified. Large air separation tower in the cold, in the cold under the valve flange on the pre-tightening time to prevent the valve does not leak at room temperature and leakage in the valve under low temperature phenomenon. When the new valve in the use of time, do not press the packing too tight, so as not to leak for the degree, so that the valve stem pressure is too large, wear accelerated, and opening and closing strenuous.