Two compressor inlet pressure switches are fitted. 63CS-1 gives an alarm at over 20mB and 63CS-2 actions a fired shutdown at over 24mB.

What would be the source of over pressure here to cause problems, I'm just trying to understand why these devices are fitted.

Thanks

 

Some questions -
1. Please check if these are 63CS series switches or otherwise
2. what are these units (mB)
3. Provide machine details

 

I believe you'll find these are actually differential pressure switches, and they are monitoring the differential pressure across some "trash screen". So, if the filters ruptured before the implosion doors opened and plugged the screens, the dp would increase.

Some older units had some very unusual filter systems; I've seen one that was a rolling "fabric" system on which the actuator was forever failing and the fabric would get clogged and then get sucked into the inlet, only partially caught by the trash screen.

There were some other equally interesting configurations employed, which usually prompted the use of these differential pressure switches to protect the compressor.

 

Jack, it is my thought that these switches are installed to measure inlet differential pressure that would be caused by dirty air filters or some other kind of inlet obstruction. First switch is an alarm, 2nd starts a normal shutdown. Our Frame 7EA has 96CS transmitters to measure inlet DP, rather than switches. Our alarm is at 6inH2O and shutdown at 8inH2O. I hope this helps. You may also refer to your control spec., it may cover this as well.

 

The positive calibration setting was the confusing issue as we have poor documentation and additional filter monitoring.

On inspection the switches are indeed DP type with the low side to the Inlet housing which explains they are indeed alarm and protection devices.

Thanks for your help.