For interlock control, should a pressure switch or a pressure transmitter be chosen?
Thread Content
For interlock control, should a pressure switch or a pressure transmitter be chosen? Is that one better? Why
In previous years, when the quality of pressure transmitters was not very stable, pressure switches were often used to provide interlock signals; as the quality of pressure transmitters has improved, more and more of them are now used for such interlock signals. But currently, MAN turbines still use pressure switches.
The cost of pressure transducers is high, while the cost of pressure switches is low; especially in many 3-to-2 configurations
To increase reliability, you can do it by using two AND gates, or by increasing the soul level, choosing one of these two options
It depends on the process requirements and the level of interlock required. Switches are inexpensive and practical, while pressure transmitters provide detailed numerical readings, giving an impression of reliability
It depends on the process requirements and the level of interlock required. Switches are inexpensive and practical, while pressure transmitters provide detailed numerical readings, appearing to be reliable; either one can be chosen
When used in SIS systems, Clause 6.1.2 of the standard GB/T 50770-2013 Design Code for Safety Instrumented Systems in Petrochemical Industries requires the use of analog signals.
Transformer voltage regulators are the preferred choice; we have gradually replaced our original switches with voltage regulators
In my opinion, pressure switches are generally used for hard interlocking, such as for controlling the start and stop of pumps, while variable frequency drives are used for process control, such as adjusting the frequency of pumps.
For pressure interlock signals in the manufacturing process, pressure transmitters are mostly used; whereas for such signals in some manufacturers of moving equipment, pressure switches are predominantly employed.
A few days ago I attended a training course, and Teacher Gao Xin said that transmitters are more stable these days, so it’s better to use them.