How to choose and install the return valve correctly
How to choose and install the return valve correctly
1. Selection of return valve:
1. The back valve is generally suitable for clean media, not suitable for containing solid particles and viscosity
larger media.
2. For low pressure return valve below DN50mm, butterfly type return valve, vertical lift return valve and diaphragm type return valve should be selected; for medium and low pressure return valve with DN greater than 200mm and less than 1200mm
For the valve, wear-free spherical upper return valve should be used; for low pressure return valve with DN greater than 50mm and less than 2000mm, butterfly type return valve and diaphragm type return valve should be used.
3. Diaphragm type return valve is suitable for pipelines that are prone to water generation. The diaphragm can well eliminate the water generated when the medium flows back, but it is limited by temperature and pressure, and is generally used in low-pressure and normal-temperature pipelines.
4. For pipelines that require relatively small or no water when the water impact is required to be closed, it is advisable to use slow-closing swing-type return valves and slow-closing butterfly-type return valves.
5. For the inlet pipeline of the water pump, the bottom valve should be selected. The bottom valve is generally only installed on the vertical pipeline of the pump inlet, and the medium flows from bottom to top;
6. The lifting type has better sealing performance and higher fluid resistance than the swing type. The horizontal type should be installed on the horizontal pipeline, and the vertical type should be installed on the vertical pipeline;
7. The installation position of the swing return valve is not limited. It can be installed on horizontal, vertical or inclined pipelines. If it is installed on a vertical pipeline, the flow direction of the medium should be from bottom to top;
8. The swing type return valve should not be made into a small diameter valve. It can be made into a very high working pressure. The nominal pressure can reach 42MPa, and the nominal diameter can also be made very large. The maximum can reach
2000mm or more. It can be applied to any working medium and any working temperature range according to the different materials of the housing and seals. The medium is water, steam, gas, corrosive medium, oil, medicine,
Wait. The working temperature of the medium is between -196--800℃.
2. Construction and installation of return valve
1. The installation position, height, and direction of inlet and outlet must meet the design requirements. Note that the direction of medium flow should be consistent with the direction of the arrow marked on the valve body, and the connection should be firm and tight.
2. Visual inspection must be carried out before the valve is installed, and the nameplate of the valve should comply with the current national standard "General Valve Mark" GB 12220. For working pressure greater than 1.0 MPa and on the main pipe
The valve that acts as a cut-off should be tested for strength and tightness before installation, and it is allowed to be used after passing the test. During the strength test, the test pressure is 1.5 times the nominal pressure, and the duration is not less than 5min.
The valve housing and packing should be qualified without leakage. During the tightness test, the test pressure is 1.1 times the nominal pressure; the test duration meets the requirements of GB 50243.
3. Do not allow the return valve to bear weight in the pipeline. The large return valve should be supported independently so that it will not be affected by the pressure generated by the piping system.
3. Installation precautions for return valve:
1. Do not allow the return valve to bear weight in the pipeline. The large return valve should be supported independently so that it will not be affected by the pressure generated by the piping system.
2. During installation, pay attention to the direction of medium flow should be consistent with the direction of the arrow on the valve body.
3. The lift-type vertical flap return valve should be installed on the vertical pipeline.
4. The lift-type horizontal flap return valve should be installed on the horizontal pipeline.
In short, in the selection and installation process of the return valve, pay attention to the above problems to avoid unnecessary losses caused by human errors.
How to correctly select and install the return valve [Part 2]
gate
The gate valve is used as a cut-off medium. When it is fully opened, the entire flow is straight, and the pressure loss of the medium is minimal at this time. Gate valves are usually suitable for applications that do not need to be opened and closed frequently and keep the gate fully open or fully closed.
working condition. Not intended for use as regulation or throttling. For high-speed flow media, the gate can cause vibration of the gate when it is partially opened, and the vibration may damage the seal of the gate and valve seat.
surface, and throttling will cause the gate to be eroded by the medium. From the structural form, the main difference is the form of the sealing element used. Depending on the form of the sealing element, gate valves are often divided into several different
Types, such as: wedge gate valve, parallel gate valve, parallel double gate gate valve, wedge double gate gate, etc. The most common forms are the wedge gate valve and the parallel gate valve.
shut-off valve
The stem axis of the globe valve is perpendicular to the seat sealing surface. The relatively short opening or closing stroke of the valve stem and a very reliable shut-off action make this valve ideal for medium shut-off or regulation
and throttling usage. Once the disc of the globe valve is in the open state, the contact between its valve seat and the sealing surface of the disc is no longer in contact, and has a very reliable shut-off action, so this valve is very suitable for
It is used for media cutting or adjustment and throttling.
Once the globe valve is in the open state, there is no longer any contact between its seat and the sealing surface of the disc, so the mechanical wear of its sealing surface is small, due to the fact that most of the globe valve's seat and disc easier
It is not necessary to remove the whole valve from the pipeline when repairing or replacing the sealing element, which is very suitable for the occasion where the valve and pipeline are welded together. The flow direction of the medium as it passes through such valves takes place
Therefore, the flow resistance of the globe valve is higher than that of other valves.
The commonly used globe valves are as follows: 1) Angular globe valve; in the angular globe valve, the fluid only needs to change direction once, so that the pressure drop through the valve is lower than that of the conventional structure. The valve is small. 2)
DC globe valve; in DC or Y-shaped globe valve, the flow channel of the valve body forms a diagonal line with the main channel, so that the degree of damage to the flow state is smaller than that of the conventional globe valve, so the pressure passing through the valve is loss
Also correspondingly small. 3) Plunger globe valve: This form of globe valve is a variation of the conventional globe valve. In this valve, the disc and seat are usually designed based on the plunger principle. Disc polished into a column
The plug is connected with the valve stem, and the sealing is realized by two elastic sealing rings sleeved on the plunger. The two elastomeric seals are separated by a collar and hold the plunger down by the load applied to the bonnet by the bonnet nut
The surrounding sealing ring is pressed firmly. Elastomeric seals are replaceable and can be made of a variety of materials, the valve is mainly used for "open" or "close", but is available with special forms of plungers or special sleeves
Rings can also be used to regulate flow.
