What are the functions of the pipeline valve?
how to install?
What does the common logo mean?
If something goes wrong, how can I repair it?
4 functions of pipeline valve
First, cut off and release media
This is the most basic function of the valve. Usually, the flow path is a straight-through valve with a small flow resistance.
Down-closed valves (stop valves, plunger valves) are less preferred due to the tortuous flow path and higher flow resistance than other valves. Where higher fluid resistance is permitted, closed valves may be used.
Second, control the flow
A valve that is easy to adjust the flow rate is usually selected as the control flow. A closed down valve, such as a shutoff valve, is suitable for this purpose because of the proportional relationship between its seat size and the stroke of the closure.
Rotary valves (plug valves, butterfly valves, ball valves) and flexible valve body valves (pinch valves, diaphragm valves) can also be used for throttling control, but they are usually only suitable for limited valve sizes.
The gate valve is a cross-cut movement of the circular valve seat with a disk-shaped gate. It can control the flow only when it is close to the closed position, so it is usually not used for flow control.
Third, commutation and diversion
According to commutation diversion needs, this valve can have three or more channels. Plug valves and ball valves are more suitable for this purpose. Therefore, most of the valves used for commutation and diversion have selected one of these types of valves.
However, in some cases, other types of valves may also be used for commutation diverting as long as two or more valves are properly connected to each other.
IV. Medium with suspended particles
When the medium contains suspended particles, it is most suitable to use a sliding valve with a wiper action along its sealing surface.
If the closing member's back and forth movement of the valve seat is vertical, it is possible to hold the particles, and therefore this valve is only suitable for a substantially clean medium unless the material of the sealing surface can allow embedded particles. Ball valve and plug valve wipe the sealing surface in the process of opening and closing, it is suitable for use in media with suspended particles.
3 installation problems for pipeline valves
First, check before installation
1. Carefully check whether the valve model and specifications meet the requirements of the drawings.
2. Check if the valve stem and the valve flap are open and whether they are stuck or skewed.
3. Check whether the valve is damaged, and whether the threads of the threaded valve are correct and intact.
4. Check whether the joint between the valve seat and the valve body is firm, the connection between the valve disc and the valve seat, the valve cover and the valve body, and the valve stem and the valve flap.
5. Check that the valve gasket, packing and fasteners (bolts) are suitable for the nature of the working medium.
6. The obsolete or long-lasting pressure reducing valve should be disassembled, and dust, sand and other debris should be cleaned with water.
7. Clear the vent cover and check the seal. The disc must be closed tightly.
Second, the general provisions of the installation
1. The position where the valve is installed should not interfere with the operation, disassembly and maintenance of the equipment, pipes and the valve body itself, and at the same time, the appearance of the assembly should be considered.
2. The valve on the horizontal pipe, with the stem installed upwards, or inclined at a certain angle, cannot be installed with the handwheel down. Valves, stems, and handwheels on high-altitude pipelines can be installed horizontally, and the chain can be opened and closed remotely using the chain at the bottom.
3. Symmetrical arrangement, neat and beautiful; the valve on the riser, under the premise of process permission, the valve hand wheel to the chest height is most suitable for operation, generally 1.0-1.2m from the ground is appropriate, and the stem must follow the operator Directional installation.
4. The valve on the side-by-side riser should have the same centerline elevation and the net distance between the handwheels should not be less than 100mm; the valves on the side-by-side horizontal pipeline should be staggered to reduce the distance between the pipes.
5. When heavy valves are installed on pumps, heat exchangers, etc., valve brackets should be provided. When the valves are operated frequently and installed on the valve more than 1.8 meters away from the operation surface, a fixed operating platform should be provided.
6. The arrow of the valve body is marked, and the direction of the arrow is the flow direction of the medium. When installing the valve, care should be taken to point the arrow at the same direction as the flow of media in the pipe.
7. When installing flanged valves, ensure that the two flange faces are parallel and concentric and do not use double gaskets.
8. When installing threaded valves, one threaded valve shall be fitted with a live connection for ease of disassembly. The setting of live connection should take into account the convenience of overhauling, which is usually the flow of water through the valve after the live connection.
Third, installation precautions
1. The valve body material of the valve is made of cast iron and it is brittle, so it must not be struck by heavy objects.
2. When carrying the valve, it is not allowed to throw; when hoisting or hoisting the valve, the rope should be attached to the valve body, and it is forbidden to pry on the hand wheel, valve stem and flange bolt hole.
3. The valve should be installed in the most convenient place for operation, maintenance and inspection. It is strictly prohibited to bury it underground. Directly buried valves and valves in the trenches shall be provided with inspection wells to facilitate opening and closing of the valves.
4. The thread should be completely intact, and when the thread is wrapped, the lead oil or the PTFE tape is twisted, the spanner must be screwed into the hex body of the tube.
5. When installing the flange valve, pay attention to tighten the connection bolt along the diagonal direction, and use even force when twisting to prevent the gasket from deviating or causing deformation and damage of the valve body.
6. The valve should remain closed during installation. For threaded valves close to the wall, it is often necessary to remove the valve stem and handwheel during installation in order to turn. When disassembling, remove the handwheel after turning the valve open.
Six common installation methods for pipeline valves
First, the valve
Also known as the gate valve, is to use the gate to control the opening and closing of the valve, by changing the cross-section to adjust the line flow and open and close the pipe. Gate valves are mostly used for the full or full closed operation of fluid media.
Gate valve installation generally does not require directionality, but it cannot be flipped.
Two. Globe valve
Valves are used to control opening and closing valves. By changing the gap between the valve flap and the valve seat, ie changing the size of the passage cross-section, the flow of medium or the passage of the media can be adjusted. Install the shutoff valve must pay attention to the flow of fluid.
The principle that must be obeyed when installing the cut-off valve is that the fluid in the pipeline passes through the valve hole from bottom to top, commonly known as “low-in and high-out”, and must not be installed reversely.
Third, the check valve
Check valve, also known as check valve, check valve, is a valve that automatically opens and closes under the pressure difference between the front and back of the valve. Its role is to make the medium flow only in one direction, and prevent the medium from flowing backward.
Check valve according to its structure, there are lifting, swinging and butterfly-clip type. Lift-type check valve has horizontal and vertical points.
When installing the check valve, you should also pay attention to the flow of the medium and do not install it.
IV. Pressure reducing valve
1. Pressure relief valves installed vertically are generally set along the wall at an appropriate height from the ground. Pressure relief valves installed horizontally are generally installed on a permanent operating platform.
2. The application of steel is loaded into the wall on the outside of the two control valves (usually used in the cut-off valve) to form a bracket, and the bypass pipe is also stuck on the bracket to level and align.
3. The pressure reducing valve shall be installed upright on the horizontal pipeline. It shall not be inclined. The arrow on the valve body shall point in the direction of the flow of the medium and shall not be reversed.
4. Shut-off valves and high and low pressure gauges shall be installed on both sides to observe the pressure changes before and after the valve. The diameter of the pipe after the pressure reducing valve should be 2#-3# larger than the diameter of the valve before the inlet valve, and the bypass pipe should be installed for overhaul.
5. The pressure equalizing pipe of diaphragm type pressure reducing valve should be connected to the low pressure pipeline. Low-pressure pipelines should be provided with safety valves to ensure the safe operation of the system.
6. When used for steam decompression, set the drain pipe. For piping systems requiring a high degree of purification, install a filter in front of the pressure reducing valve.
7. After the installation of the relief valve assembly is completed, pressure relief valves and safety valves shall be pressure tested, flushed and adjusted according to design requirements, and signs shall be made after adjustment.
8. When flushing the pressure reducing valve, close the pressure reducer inlet valve and open the flushing valve for flushing.
Five, steam trap
1. Cut-off valve (stop valve) should be installed before and after, and a filter should be installed between the trap and the front shut-off valve to prevent dirt in the condensate from blocking the trap.
2. Between the trap and the cut-off valve should be set to check the pipe, used to check whether the work of the trap is normal, such as open the check tube a lot of steam, then the trap is broken, need to repair.
3. The bypass pipe is provided to discharge a large amount of condensate at startup and reduce the displacement load of the trap.
4. When the trap is used to remove condensed water from the heating equipment, it should be installed in the lower part of the heating equipment, so that the condensate pipe is vertically returned to the trap to prevent it from being stored.
5. The installation position should be as close as possible to the drainage point. If the distance is too far away, air or steam will accumulate in the slender pipeline in front of the trap.
6. Hydrophobic issues should be considered when the steam pipeline is too long.
Six, safety valve
1. Before the installation, the product must be carefully inspected to verify whether there is a certificate of conformity and product specification to clarify the constant pressure condition at the time of delivery.
2. Safety valves should be placed as close to the platform as possible for inspection and maintenance.
3. The safety valve should be installed vertically. The medium should be discharged from the bottom up and the stem should be checked for verticality.
4. Under normal circumstances, cut-off valves can not be installed before and after the safety valve to ensure safety and reliability.
5. Safety valve pressure relief: When the medium is liquid, it is generally discharged into the pipeline or closed system; when the medium is gas, it is generally discharged to the outside atmosphere.
6. The oil and gas medium can generally be discharged into the atmosphere, and the outlet of the safety valve vent pipe should be 3m higher than the surrounding highest structure. However, the following conditions should be enclosed in a closed system to ensure safety.
7. The diameter of the population pipeline shall be equal to the diameter of the inlet pipe of the valve; the diameter of the discharge pipe shall not be less than the diameter of the outlet of the valve. The discharge pipe shall be led to the outside and shall be installed with the elbow so that the outlet of the pipe will face the safe zone.
8. When the safety valve is installed, when the connection between the safety valve, the equipment and the pipeline is open hole welding, the diameter of its opening shall be the same as the nominal diameter of the safety valve.
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