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Valve installation knowledge and precautions
- Jan 29, 2018 -

Valve Installation Requirements

The quality of the valve installation directly affects the use of the valve, therefore, the introduction of construction units and production units of the high priority

Valve installation should be in accordance with the valve instructions and the relevant provisions. The construction process should be carefully inspected, carefully constructed. Valve before installation, test pressure before the installation, carefully check the specifications of the valve, the model is consistent with the drawings, check the valve is intact, whether the valve is flexible rotation, sealing surface damage, etc., confirm the correct, you can install.

Valve installation, the operating mechanism of the valve from the operation of the most suitable for the ground around 1.2m, will be aligned with the chest. When the valve center and handwheel away from the operation of the ground more than 1.8m, the operation of more valves and relief valve set operating platform. Valve more pipe, the valve as far as possible to concentrate on the platform in order to operate.

For a single valve exceeding 1.8m and not often operated, the sprocket, extension bar, movable platform and movable ladder can be used. When the valve is installed under the operating surface, the extension rod should be set, the ground valve should be set up to the well, for the sake of safety, the ground well should be stamped.

The valve stem of the valve on the horizontal pipe, preferably vertically upwards, is unfavorable to install the stem downward. Stem downward installation, inconvenient operation, inconvenient maintenance, but also easy to corrode valve accident. The floor valve does not skew installs, lest the operation is inconvenient.

The valve on the side line should be operated, repaired and disassembled, the net distance between the handwheel is not less than 100mm, if the pipe distance is narrower, the valve should be staggered and arranged.

For the open force, low strength, brittleness and weight of the larger valves, before installation to set the valve frame support valve to reduce start-up stress.

When installing a valve, the pipe close to the valve uses the pipe clamp, and the valve itself uses an ordinary wrench. At the same time, the installation, to make the valve in a semi closed state, to prevent the valve rotation and deformation.

The proper installation of the valve should make the internal structure form conform to the flow of the medium, and the installation form conforms to the special requirements and operation requirements of the valve structure. Special is to pay attention to the flow of media requirements of the valve should be installed according to the requirements of the process pipeline. The layout of the valve should be convenient and reasonable, the operator is easy to approach the valve, for the lifting valve stem valve, to set aside the operating space of all valve stem to be as far as possible to install and perpendicular to the pipe.

Installation of valve connection surface

The installation end adopts the threaded connection valve, should make the thread twist into the valve the depth is suitable, the thread twists into the deep pressure valve seat, will affect the valve seat and the gate good coordination, twists into too shallow, will affect the joint the sealing reliability, easy to introduce the leakage. At the same time threaded sealing materials should be used to tetrafluoroethylene raw tape sealant, pay attention not to the sealing material to the valve cavity.

For the valve connected to the flange end, the first is to find the connecting surface of the positive flange, the cover is perpendicular to the pipeline, and the bolt hole should be right. Valve flange should be parallel to pipe flanges, flange clearance is moderate, should not be wrong mouth, tilt and other phenomena, flange between the heart gasket should be placed in the middle, not oblique, bolts should be evenly tightened. Prevents the forced connection tightening during valve installation to produce an additional residual force.

Thoroughly remove the dirt from the inner and outer threads of the pipe before installation, and remove the dirt, slag and other sundries in the pipe before the pipe is connected, removing the burr and foreign matter which hinder the flow of the media and may affect the operation of the equipment. Prevent damage to the valve sealing surface or plug the valve.

Install welded end connection valves, should be a group of spot welding valve at both ends of the weld, open the valve, and then weld the welding process card welding seam, weld the appearance and internal weld quality inspection, to ensure that no hole, slag, crack, etc.

installation of heavier valves

When installing heavier valves (dn>100), using lifting tools or equipment, the lifting ropes should be fastened to the flange or bracket of the valve, and should not be fastened to the handle-type stem of the valve to avoid damaging the valve.

What are the general requirements for valve installation?

A: The general requirements of valve installation, the most suitable height of installation, horizontal pipe on the valve, stem direction is as follows:

(1) The valve should be located in a place accessible, easy to operate and maintain. The valves on the rows (such as the pipes to and from the device) should be centrally arranged and the operating platform and ladders should be considered. The center line of the valve on the parallel arrangement pipe shall be as Chinzi as possible. The net distance between the handwheel should not be less than 10Qmm, in order to reduce the pipe spacing, the valve can be staggered layout;

(2) frequently operated valve installation position should be easy to operate, the most suitable installation height for the distance from the operating surface of 1.2m up and down. When the valve Handwheel Center height exceeds the operating 2m, for the centralized arrangement of the valve group or frequent operation of separate valves and safety valve should be set up platform for the operation of the individual valves should also take appropriate measures (such as sprocket, extension bar, movable platform and activity ladder, etc.). Chain chains should not hinder passage. The valve on the piping and equipment of the dangerous medium shall not be installed in the height of the head of the person to avoid touching the head of the person, or to injure the face of the person directly because of the leakage of the valve;

(3) partition equipment with the valve should be directly connected with the device pipe or near the equipment. A valve connected to a pipe which is an extremely hazardous and highly hazardous toxic medium shall be directly connected with the equipment valley, and the valve shall not be operated by a sprocket wheel;

(4) Accident treatment valve such as fire water valve, fire steam two valves should be dispersed layout, and take into account the safety of the operation of the accident. This type of valve should be arranged behind the control room. Safety wall, outside the factory door, or with the accident occurred at a certain safe distance zone; In order to have a fire accident, the operator can operate safely;

(5) In addition to special requirements of the process, towers, reactors, vertical containers and other equipment on the bottom of the pipe valve, shall not be arranged in the skirt;

(6) The cut-off valve of horizontal branch from the dry pipe should be arranged on the horizontal pipe tube near the root;

(7) Lift check valve should be installed in the horizontal pipe, vertical lift check valve should be installed in the pipe medium from the bottom of the vertical pipe flow. The swing check valve should be installed on the horizontal pipe first, can also be installed in the pipe medium from bottom to top flow vertical pipe, the bottom valve should be installed in the centrifugal pump suction installation height, butterfly check valve can be selected, the pump outlet and the connected pipe diameter is inconsistent, you can choose the different diameter check valve;

(8) Layout in the operating platform around the valve Handwheel Center distance of the operating platform is not more than 450mm, when the stem and handwheel into the platform above and the height is less than 2m, should make it does not affect the operation of operators and pass;

(9) The valve of the underground pipe should be located in the trench or the valve well, if necessary, the valve extension bar should be set. The fire water valve well should be marked;

(10) Horizontal pipe valve, valve stem direction can be determined in the following order: vertical upward, horizontal, upward tilt 45°, downward tilt 45°;

(11) Valve stem horizontal installation of the open bar valve, when the valve opened, the stem shall not affect the passage.

Check valve installation needs attention

(1) Installation position, height, import and export direction must meet the design requirements, pay attention to the direction of the media flow should be aligned with the direction of the valve body, the connection should be strong and tight.

(2) The valve must be installed before the appearance inspection, the valve nameplate should be in line with the current national standard "general valve Mark" GB 12220 of the provisions. For the work pressure is greater than 1.0 MPA and in the main tube to play a cut-off valve, the installation should be carried out before the strength and tightness test, qualified to use the rear. Strength test, the test pressure of 1.5 times times the nominal pressure, duration of not less than 5min, valve housing, fillers should be no leakage for qualified. In the tightness test, the test pressure is 1.1 times times of the nominal pressure, and the duration of the test meets the requirement of GB 50243.

(3) Do not allow the check valve to bear the weight in the pipeline, the large check valve (Aetv one-way valve): should be supported independently, so that it is not affected by the pressure produced by the pipe system.

Technical Requirements for valve installation

1. Directional. The valve body of the general Valve has a mark, the direction that the arrow refers to is the direction that gas flows forward. Special attention must be paid to the counter. Because of a variety of valve requirements of gas one-way flow, such as relief valve, valve, check valve, throttle valve, for the cut-off valve in order to facilitate the opening and maintenance, but also required gas from the bottom through the seat, but the gate valve, plug installation, not limited by the direction of circulation.

2. Installation location. To the valve long-term operation and maintenance considerations, as convenient as possible operation and maintenance, but also pay attention to the appearance of the assembly.

Valve handle direction can be vertical upward, can also tilt to a certain angle or level, but the hand wheel should not be downward to avoid the face operation; The handwheel of the landing valve is the best chest height, easy to open and close; the gate valve can not be used underground to prevent the stem from being corroded.

Some valve installation location has special requirements, such as pressure relief valve upright installed in the horizontal pipe, no tilt, lift check valve required disc vertical; Swing check valve requires pin shaft level. In short, according to the principle of the valve to determine its installation position, otherwise the valve can not work effectively, or even ineffective.

3. Plug installation. Check the specification model, identify if there is damage, remove the thread mouth cover and excessive grease and sundries inside the thread, check the sealing performance of the plug. Gas plug in the installation must pay attention to the appropriate force, according to the size of the plug to choose different specifications of the pipe pliers or wrenches to install.

4, The Wire buckle valve installs, the valve company should ensure the thread intact, can use spanner wrench, do not use the tube clamp, avoids damaging the body appearance.

5, flange-type valve installation, must ensure that the two flange sections parallel to each other and on the same axis, tightening bolts should be cross cross, so that the valve end of the force evenly.

6, the flange and the threaded connection valve should be installed in the shutdown state. Butt welding valve and pipe connection, weld bottom should use argon welding, to ensure the internal cleaning, welding, the valve should not be closed to prevent heat deformation.

7, under normal circumstances, the valve and corrugated telescopic joint directly connected, it should be based on valve and corrugated telescopic joints and the size of flanges and gaskets, the two sides of the pipeline cut off, leaving the installation location.

8, the valve hoisting, the rope can not be tied in the first round or stem, to prevent damage, should be light hanging, handle, not collide. On the pier, according to the required elevation cushion stability, cushion flat. The valve must have a solid pier or bracket to hold the valve and not allow the valve to be suspended to generate stress.