In fluid system, valve is a device used to control the direction, pressure and flow of fluid. In the construction process, the quality of valve installation directly affects the normal operation in the future, so it must be paid great attention by the construction unit and production unit.

Installation of valves

The valve shall be installed in accordance with the valve operation manual and relevant regulations. Careful inspection and careful construction shall be carried out during construction. Before installing the valve, it shall be installed only after the pressure test is qualified. Carefully check whether the specification and model of the valve are consistent with the drawings, whether all parts of the valve are intact, whether the opening and closing valve rotates flexibly and freely, and whether the sealing surface is damaged. After confirmation, it can be installed.

When installing the valve, the operating mechanism of the valve should be about 1.2m away from the operating ground, which will be flush with the chest. When the center of the valve and the hand wheel are more than 1.8m away from the operating ground, the operating platform shall be set for the valves and safety valves with more operations. For pipelines with many valves, the valves shall be concentrated on the platform as far as possible for easy operation.

For a single valve that exceeds 1.8m and is not operated frequently, equipment such as sprocket, extension rod, movable platform and movable ladder can be used. When the valve is installed below the operating surface, an extension rod shall be set, the ground valve shall be set with a ground well, and the ground well shall be covered for safety.

The valve stem of the valve on the horizontal pipeline should be vertically upward, and the valve stem should not be installed downward. The valve stem is installed downward, which is inconvenient for operation and maintenance, and is easy to corrode the valve and cause accidents. The floor valve shall not be installed obliquely to avoid inconvenient operation.

Valves on side-by-side pipelines shall have space for operation, maintenance and disassembly, and the clear distance between hand wheels shall not be less than 100mm. If the pipe distance is narrow, the valves shall be staggered.

For valves with large opening force, low strength, high brittleness and heavy weight, a valve frame shall be set to support the valve before installation to reduce the starting stress.

When installing the valve, use a pipe wrench for the pipe close to the valve, and use an ordinary wrench for the valve itself. At the same time, during installation, the valve shall be semi closed to prevent rotation and deformation of the valve.

The correct installation of the valve shall make the internal structure conform to the flow direction of the medium, and the installation form conform to the special requirements of the valve structure and operation requirements. Special attention shall be paid to the installation of valves with medium flow direction requirements according to the requirements of process pipeline. The arrangement of valves shall be convenient and reasonable, and the operators shall have easy access to the valves. For the lifting stem valves, the operation space shall be reserved, and the stems of all valves shall be installed upward and perpendicular to the pipeline as far as possible.

Installation of valve connecting surface

When installing the valve with threaded connection at the end, the depth of the thread into the valve shall be appropriate. If the thread is screwed too deep and compresses the valve seat, it will affect the good cooperation between the valve seat and the gate. If the thread is screwed too shallow, it will affect the sealing reliability of the joint and easy to introduce leakage. At the same time, the thread sealing material shall be Teflon raw tape or sealant.

For the valve connected at the end of the flange, first align the connecting surface of the flange, the cover is perpendicular to the pipeline, and the bolt hole should be aligned. The valve flange shall be parallel to the pipe flange, the flange clearance shall be moderate, and there shall be no misalignment, inclination and other phenomena. The center gasket between flanges shall be placed in the center without deflection, and the bolts shall be tightened symmetrically and evenly. Prevent forced connection tightening during valve installation, resulting in an additional residual force.

Before installation, the dirt on the inner wall and external thread of the pipe shall be completely removed; Remove burrs and foreign matters that hinder medium flow and may affect equipment operation, and blow out dirt, slag and other sundries in the pipeline before pipe connection. Prevent damaging the sealing surface of the valve or blocking the valve.

When installing the connecting valve at the welding end, first assemble the welded junctions at both ends of the valve after spot welding, open the valve, and then weld the weld according to the welding process card. After welding, check the appearance and internal weld quality of the weld to ensure that there are no pores, slag inclusions, cracks, etc. if necessary, the weld shall be subject to shot line or override inspection.

Installation of heavy valves

When installing heavy valves (DN > 100), lifting tools or equipment shall be used. The lifting rope shall be tied to the flange or support of the valve, not to the handle valve stem of the valve, so as to avoid damaging the valve.

What are the general requirements for valve installation?

The general requirements for valve installation, the most suitable installation height and the direction of valve and valve stem on horizontal pipeline are as follows:

1. The valve shall be located at a place easy to access, operate and maintain. Valves on rows of pipelines (such as pipelines entering and leaving the device) shall be arranged in a centralized manner, and operation platforms and ladders shall be considered. The center line of the valve shall be arranged as parallel as possible. The clear distance between hand wheels shall not be less than 100mm. In order to reduce the pipe spacing, the valves can be staggered;

2. The installation position of frequently operated valves shall be convenient for operation, and the most suitable installation height is 1.2m up and down from the operating surface. When the height of the center of the valve handwheel exceeds the operating surface by 2m, a platform shall be set for the centrally arranged valve group or the individual valves and safety valves operated frequently, and appropriate measures shall also be taken for the individual valves operated infrequently (such as sprocket, extension rod, movable platform, movable ladder, etc.). The chain of the sprocket shall not obstruct the passage. Valves on pipelines and equipment with hazardous media shall not be installed within the height range of human head, so as to avoid hurting human head or directly hurting human face due to valve leakage;

3. The valve for isolating the equipment should be directly connected with the equipment nozzle or close to the equipment. The valve on the pipeline connected with the equipment with extremely hazardous and highly hazardous toxic media shall be directly connected with the equipment port, and the valve shall not be operated by sprocket;

4. Accident treatment valves, such as fire water valve and fire steam valve, shall be distributed, and the safe operation in case of accident shall be considered. Such valves shall be arranged behind the control room. Behind the safety wall, outside the plant door, or a certain safe distance from the accident; So that operators can operate safely in case of fire accident;

5. Except for the special requirements of the process, the valves on the bottom pipes of towers, reactors, vertical vessels and other equipment shall not be arranged in the skirt;

⒍ the shut-off valve of the horizontal branch pipe led from the main pipe should be set on the horizontal pipe section near the root;

⒎ the lift check valve shall be installed on the horizontal pipe, and the vertical lift check valve shall be installed on the vertical pipe where the medium in the pipe flows from bottom to top. The swing check valve shall be preferentially installed on the horizontal pipeline or the vertical pipeline in which the medium flows from bottom to top; The bottom valve shall be installed at the installation height of centrifugal pump suction, and butterfly check valve can be selected; When the diameter of the pump outlet is inconsistent with that of the connected pipeline, the reducing check valve can be selected;

8. The distance between the center of the hand wheel of the valve arranged around the operating platform and the edge of the operating platform should not be greater than 450mm. When the valve stem and hand wheel extend above the platform and the height is less than 2m, it should not affect the operation and passage of the operator;

⒐ the valve of underground pipeline shall be set in the pipe trench or valve well. If necessary, the valve extension rod shall be set. The fire water valve well shall have obvious signs;

⒑ for valves on horizontal pipelines, the valve stem direction can be determined in the following order: vertical upward; Level; 45 ° upward tilt; 45 ° downward tilt; Do not go down vertically;

⒒ for the rising stem valve with horizontal valve stem, when the valve is opened, the valve stem shall not affect the passage.