Vacuum monitoring

[bwgill]

We have a central vacuum system that runs at 27Hg, I need to build or buy a sensoring device to alarm low or high vacuum. I am lookoing for any ideas or suggestions

 

[danw2]

Use a pressure/vacuum switch. Pipe the threaded connection to the process.
Wire the switch output to drive whatever you're thinking is going to be the alarm.

United Electric model H100-218 uses wetted brass/bronze sensor. No scale for adjusting the trip point.
H400-S126B uses 316SS wetted sensor, has an scale for adjusting the trip point.

Or you can use a gauge pressure/vacuum transmitter feeding an analog signal to an indicator with alarm relays or an alarm module.

Avoid the distributor who mistakenly tells you that you need an 'absolute' pressure anything. When you use terms like 27"Hg, then your vacuum is gauge pressure vacuum, referenced to atmosphere, not absolute pressure, referenced to absolute zero.

 

[Skogsgurra]

27Hg could mean anything. In Europe, it means either 27 mm Hg absolute or "underpressure" and elsewhere, it might mean 27" (inches) Hg. How can we tell? And, what exactly does the OP mean by 27Hg?

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[roydm]

Why not use a 4-20 mA transmitter, not much more money than a good pressure switch then your control system can be set to alarm at as many different pointa as you like.
Either a gauge type set for a negative pressure or if your process is effected by the ambient pressure changes an Absolute range transmitter.

Roy

 

[controlsdude]

Depends where they are used?

Contact type self contained for shutdown device around the PLC for too much vacuum? damage to equipment or collaspe the vessel if too much vacuum similar to an estop input.

Or like above using a 4-20mA type vacuum to see the vacuum setting?

 

[moggie]

Have a look at IFM

http://www.ifm.com/ifmus/web/pmain040_010_010_030.htm

Analog and switch points on the same device - and very reliable

 

[HEC]

The OP must provide more information, as Controlsdude has asked, what is the purpose for the switching? This will determine class and reliability of the switch.

Also range of the measurement is ir 27 mm Hg or 27" Hg very diferent measurement accuracy needed.

Mark Hutton