It is inevitable to involve the selection of check valves when designing pipelines for petrochemical plants due to the wide variety of check valves. The reasonable selection of check valves not only affects the investment in engineering construction and the normal production of the device, but also affects the safety of the pipeline system and equipment. Therefore, the selection of check valves is very important, and the main factors affecting the selection of check valves are as follows:
(1) Understand the purpose of setting check valves in the process and meet process requirements.
When there are special requirements for the structure of the check valve in the process, it should generally be indicated in the PID (Process Pipeline Instrument Flow Diagram).
(2) Meet the requirements for pressure drop.
Some pipelines have particularly requirements for strict pressure drop, and the check valves on these pipelines need to use low pressure drop check valves; double plate check valves are commonly used. If necessary, simulation calculations are also needed to determine whether the pressure drop meets the design requirements.
(3) Meet the requirements for operating pressure.
For large diameter check valves with particularly low operating pressure, if a standard pressure rating swing check valve or lift check valve is selected, the valve disc may be heavy and unable to open under normal operating conditions. For high-pressure check valves with high operating pressure, check valves with pressure sealed valve covers can be selected.
(4) Impact of valve size
Generally, lift check valves are commonly used for check valves with a nominal diameter less than DN50. When the nominal diameter is greater than or equal to DN50 and less than DN400, a swing check valve can be selected. When the nominal diameter is greater than DN400 and less than DN600, a disc check valve can be selected. When the nominal diameter is greater than DN50 and less than DN1200, a double plate check valve can be selected.
(5) Impact of installation direction
Lift check valves without springs should be installed on horizontal pipelines. Swing check valves and titling check valves are generally installed on horizontal pipelines. Plate check valves and axial flow check valves can be installed horizontally or vertically.
(6) Impact of installation space
For larger diameter check valves, when the installation space is small, a wafer double plate check valve can be selected.
(7) Economic impact
When multiple check valves can meet the requirements, priority should be given to selecting check valves with simple structure and low price. In petrochemical plants, the most used types are lift check valves and swing check valves. The selection of check valves should not only consider the influence of a single factor, but often the result of a comprehensive consideration of multiple factors.