1. General requirements for valve installation
(1) The valve installation position shall not interfere with the operation and maintenance of the equipment, piping and the valve itself. The optimum installation height is about L. 2 m from the operation surface. When the height of the handwheel center of the valve exceeds 2M, a platform should be provided for the valve group centrally arranged or the separate valves and safety valves frequently operated Appropriate action should also be taken for infrequently operated valves (E. G. sprockets, extension rods, platforms, or ladders) . Sprocket chains shall not obstruct passage. Valves on pipes and equipment containing dangerous media shall not be installed within the height of a person’s head to avoid injury.
(2) The stem of a valve in horizontal piping is preferred to be vertically up or to the left or right 45. Horizontal mounting is also acceptable, but not downward. The valve stem on the vertical line faces the face, but care should be taken not to affect access.
(3) For higher quality valves, support shall be provided nearby, the distance between valve flange and support shall be greater than 300mm; for large valves, lifting conditions shall be considered.
(4) Place valves on parallel lines with their centerlines aligned as far as possible. Handwheel clearance should not be less than 100 mm. Valves should be installed as close to the main pipe and equipment as possible. The valve connected with the equipment nozzle can be directly connected if the nominal pressure, diameter and sealing surface form are the same or corresponding with the flange of the equipment nozzle. The branch pipe leading from the main pipe shall generally be provided with a cut-off valve near the root and on the horizontal pipe section.
(5) Lift check valve should be installed on horizontal pipe section; vertical lift check valve can be installed on vertical pipe; swing check valve should be installed on horizontal pipe priority, can also be installed in the pipe media flow from bottom to top of the vertical pipe. The bottom valve should be installed at the end of the suction pipe of the centrifugal pump; the pressure reducing valve and regulating valve should be installed vertically on the horizontal pipe. Valves for underground pipelines shall be located in trenches or valve wells. Fire water valve wells shall be clearly marked and installed vertically on the equipment or piping.
2. Installation of pressure reducing valve
Pressure relief valve group should not be located close to mobile equipment or vulnerable to impact, should be located in small vibration, enough space and easy maintenance. In order to overhaul needs, the pressure-reducing valve group should be equipped with cut-off valve and bypass valve. To prevent impurities from wearing away, set a y-shaped filter in front of the relief valve. Safety valve should be set after the valve group, when the pressure exceeds the set value, can play the role of pressure relief. Steam system before the pressure-reducing valve group, should be set up steam trap or steam water separator. Valve group should be set at the bottom of the pilot valve.
The installation height of the pressure reducing valve group is about 1.2m above the ground, which can be laid along the wall, and about 3m above the ground, which can be laid along the wall, but a permanent operation platform should be set up. The pressure relief valve should be installed on the horizontal pipe. Bellows Relief Valves shall be installed downward when steam is used and upward when air is used.
3. Installation of safety valve
(1) The safety valve on the equipment container should be installed vertically at the opening of the equipment container and on the pipeline near the outlet of the equipment container as far as possible, but the nominal diameter of the pipeline should not be less than the nominal diameter of the safety valve inlet.
(2) The separate air relief valve shall be provided with a regularly opened shut-off valve at its inlet and sealed with lead. A lead-sealed, regularly opened shut-off Valve shall be installed at the inlet and outlet of the relief valve that is discharged into a closed system or into the atmosphere using a manifold. The cut-off valve should choose the rising stem type gate valve or the stopcock with better sealing performance.
(3) The liquid safety valve is generally discharged into the sealing system, the gas safety valve is discharged into the atmosphere. The outlet of the vent pipe of the gas relief valve discharged into the atmosphere should be 2.5 m above the operation surface and led to the outside. The outlet of the vent pipe of the safety valve for the discharge of flammable and toxic gases into the atmosphere shall be 2 m above the highest building or equipment in the vicinity. If there is an open flame within a horizontal distance of 15M, the combustible gas shall not be discharged into the atmosphere.
The maximum pressure loss of the inlet piping of the relief valve shall not exceed 3% of the constant pressure of the relief valve. To this end, in addition to the location of the safety valve should be as close as possible to the protected equipment and pipeline, can also be used to increase the diameter of the inlet pipe (comparable valve inlet diameter 1~3 block) , using a long radius elbow or using a pilot-type safety valve to solve.
(5) The pressure loss of the outlet pipeline of the Safety Valve should not be too large, so as to avoid the back pressure of the safety valve is too large. The back pressure of common type should not exceed 10% of the constant pressure of safety valve; the back pressure of corrugated type (balanced type) should not exceed 30% of the constant pressure of safety valve; the back pressure of pilot type safety valve should not exceed 60% of the constant pressure of safety valve. The end of the outlet pipe can be cut into a flat opening so that the discharge can be discharged directly upward at high speed. If the outlet pipe is too long, it should be well fixed to prevent vibration.
(6) When designing the bracket on the pipeline equipped with safety valve, the high-speed discharge of gas or steam into the atmosphere should be considered, which produces the opposite force on the Central Line of the outlet pipe. The reaction of the relief valve can be calculated.
4. Installation of Control Valve
(1) The installation position of the Control Valve shall meet the design requirements of the Piping System (process flow) , and shall be as close as possible to the on-site indicator (primary meter) associated with it, and as close as possible to the position of the measuring element to facilitate manual operation of the by-pass Valve Can observe an instrument value once. Regulator should be vertical vertical vertical installation in the horizontal pipeline, under special circumstances can be horizontal or inclined installation, but to add support.
(2) In order to facilitate the operation and maintenance, reduce the occupation of land, the Control Valve Group should be arranged as far as possible in the ground by the wall, by the equipment or platform and other easily accessible places. Clearance with platform or ground shall not be less than 250mm.
(3) Control valve should be installed in the environment temperature not higher than 60℃ and not lower than-40℃ place, should be away from the vibrator, to avoid the impact of fire hazard.
(4) Control valves are generally installed by-pass and by-pass valves. The by-pass valve is mainly used for regulating the flow when the maintenance is stopped, so the cut-off valve should be generally chosen. But when the by-pass valve DN≥150mm, the gate valve can also be used. Before and after the regulation of the cut-off valve should first use the gate valve, because its resistance is small, close tight. General control valve before and after the size of the head, should immediately follow the installation of the control valve. In order to relieve the pressure and clear the pipe between the two shut-off valves during the overhaul of the control valve, the liquid drain valve DN=15mm can be set at the lowest point of the pipe between the shut-off valves upstream of the inlet side of the control valve. In addition, it is advisable to add a filter after the inlet cut-off valve and before the regulating valve (if the regulating valve DN<25 mm, a filter must be added). The clear distance between the regulating valve head and by-pass pipe and the direction of the outer wall of the valve shall not be less than 300mm.
(5) Watch the flow direction when installing the regulator (arrow on the regulator) . The control valve group shall have reliable support. There shall be a regulating valve bracket on the hot extension pipe. One of the two brackets shall be a fixed bracket and the other shall be a sliding bracket.
5. Installation of thermal expansion valve
Thermal expansion valve installed in the condenser (or reservoir) and the evaporator pipe, the valve body should be vertical installation, not inclined, more can not be installed upside down. Whether the position of the temperature-sensitive package of the thermal expansion valve is reasonable or not has obvious influence on whether the liquid supply to the evaporator can be adjusted reasonably by the thermal expansion valve. Generally speaking, the temperature sensor should be installed on the horizontal straight pipe of the evaporator outlet, and the distance from the air intake of the compressor should be over 1.5m cold insulation should be carried out together with the pipeline to reduce the influence of ambient temperature on the temperature sensor.
Post time: Nov-25-2021