Due to the more types of check valves, in the petrochemical plant pipeline design, inevitably involves the selection of check valves. Whether the selection of check valve type is reasonable, not only affects the investment in construction and normal production of the device, but also affects the pipeline system and the safety of the equipment.
Therefore, the selection of check valve is very important, the main factors affecting the selection of check valve type are as follows:
1. First of all, we should understand the process to set the purpose of the check valve to meet the process requirements. When the process has special requirements on the structure of the check valve, generally should be indicated in the PID (process piping instrumentation flow chart). Such as reciprocating compressor outlet pipeline, the process will require the use of non-shock check valve, the purpose is to avoid frequent fluctuations in the outlet pressure due to reciprocating compressor, resulting in frequent opening of the valve flap and impact, resulting in damage to the check valve. For the export and inlet pressure difference greater than 4.0MPa centrifugal pump, the process generally requires the pump outlet pipeline set up on a different type of double check valve. This is due to the pump outlet and inlet pressure difference is large, the pump suddenly stops running, the leakage of the check valve is larger, in order to reduce the leakage of the check valve, while reducing the chances of check valve damage failure, so the use of two different types of check valves.
2. Should meet the requirements of the pressure drop. Some pipeline pressure drop requirements are particularly stringent, these pipeline check valves should be used on the low pressure drop check valve, commonly used double-plate check valve. If necessary, it is also necessary to carry out simulations to determine whether the pressure drop to meet the design requirements.
3. operating pressure requirements. For large-diameter check valves with particularly low operating pressure, if the standard pressure level of swing check valves or lift check valves are selected, the valve may be heavy due to the flap, resulting in normal operating conditions, the flap can not be opened. As for the high pressure check valve with high operating pressure, the check valve with pressure sealing bonnet can be selected.
4. Influence of valve size. In general, the nominal diameter of less than DN50 check valve commonly used lift check valve; nominal diameter greater than or equal to DN50, less than DN400, can choose to rotary check valve; nominal diameter greater than DN400, less than DN600, can choose to inclined disc check valve; nominal diameter greater than DN50, less than DN1200, can choose to double-plate check valve.
5. Influence of installation direction. The lift check valve without spring should be installed on the horizontal pipeline; rotary check valve and tilting disc check valve are generally installed on the horizontal pipeline, can also be installed in the medium from the bottom upward flow of vertical pipeline or inclined pipeline; double-plate check valve, axial flow check valve can be installed both horizontally and vertically.
6. The influence of installation space. For larger caliber check valves, when the installation space is small, you can choose to clamp double-plate check valve.
7. The impact of economy.
When a variety of check valves can meet the requirements, should give priority to simple structure, low-priced check valve.
Petrochemical plant, the largest amount of lift check valve and swing check valve. Check valve selection, can not only consider the impact of a single factor, often a combination of factors to consider the results.