Hi
I am working on a instrument procure project. My problem is about Pressure Switches (or generally about field switches).

1- Is there any pressure switch which is "hermetically sealed" and "switch rating 5A, 24 VDC" simultaneously? why?

2- Is there any pressure switch which has "DPDT contact" and "adjustable dead band" simultaneously? why?

Your kind reply is highly appreciated
Saeid

 

>1- Is there any pressure switch which is "hermetically sealed" and "switch rating 5A, 24 VDC" simultaneously? why?<

Yes. The hermetically sealed issue is often for use in hazardous areas. I don't know why someone would spec a 24VDC 5A switch. Maybe they just looked up the spec on the switch thpe normally use and that is what it happens to be.

>2- Is there any pressure switch which has "DPDT contact" and "adjustable dead band" simultaneously? why?<

Yes. Adjustable deadband is a common process requirement so it is commonly avaialble on pressure switches.

It sounds to me like you have no experience in the control field to be asking such very basic questions.

 

United Electric 12 series for hermetically sealed switches:
http://www.ueonline.com/products/prod_hazard.htm

100 Series, Pressure, Differential Pressure
SPDT or DPDT switch output
Internal reference scale and adjustable deadband available
http://www.ueonline.com/products/prod_gen.htm

 

Dear Bob
I agree with you that my questions are a little unusual. In our current project we quoted pressure & level switches as "hermetically sealed" and "switch rating 5A, 24 VDC", according to our owner comment. But now some vendors say us that there isn't any such switch!!!

So regardless of possibility of having two options "hermetically sealed" and "switch rating 5A, 24 VDC" simultaneously, have you seen any pressure & level switches with above specifications, in your projects???

 

Dear David
In your proposed switch there isn't any switch with "hermetically sealed" and "switch rating 5A, 24 VDC", simultaneously. I don't know why don't vendors quote such switch!!

 

Saied,

Perhaps you need to return to your Customer and ask them to clarify the "hermetically sealed" requirement. It's possible they are referring to devices rated for hazardous atmospheres, "explosion-proof": Class I, Div. 2, Group D; etc.

I've heard of hermetically sealed refrigeration compressors, but never hermetically sealed pressure switches.

The English language can be very misleading in technical terms. Many times two people can be talking about exactly the same thing, and yet the terms and words are completely different.

Also, a manufacturer's representative who sells instruments and devices for many different manufacturers is a very good resource to cultivate when trying to find equipment. You can forward this kind of query to them for comment and bid, and they can provide clarification or suggestions.

But, really, you need to return to your Customer and clarify the terminology. Have you looked up the term "hermetically sealed" to see what it means? Here is a portion of the wikipedia.org definition:

"...A hermetic seal is a seal which, for practical purposes, is considered airtight...."

This reeks of "explosion-proof-" or "hazardous atmosphere-" rated. But, try to understand what your Customer needs this device for, and get them to clarify what they want. You'll both be happier with the results the first time around. It's likely if you continue assuming what they want based on a vague or misleading term, you'll be re-ordering something again. And nobody will be happy about that.

 

Oops, you're right, no hermetically sealed switches in the 100 series, but there are in the 117 series:

Sorry, I sent you to the wrong model for hermetically sealed switches.

The 117 series has hermetically sealed switches. However, adjustable deadband is not available.

http://www.ueonline.com/bulletins/117-b.pdf

* Hermetically sealed snap switch, SPDT or DPDT output

Switch output: One SPDT hermetically sealed snap action switch; switch may be wired “normally open” or “normally closed”; DPDT (option 1190/1195)

Electrical rating: 11 A 125/250 VAC resistive; 5 A @ 28 VDC; 1 A @ 48 VDC; 1/2 A @ 125 VDC; switch

Switch Options*
1190: Hermetically sealed, DPDT, 11 A 125/250 VAC, products set on rising pressure or temperature only. Due to inherent separation of circuits on falling pressure or temperature, specify Option 1195 if setting on fall is required. Deadband and minimum set point will increase. Not available models 523, 533

1195: Hermetically sealed, DPDT, 11 A 125/250 VAC; products set on falling pressure or temperature only. Due to inherent separation of circuits on rising pressure or temperature, specify Option 1190 if setting on rise is required. Deadband and minimum set point will increase. Not available models 523, 533

Options:
M405 intrinsic safety compliance for European Union per ATEX standards
M406 Intrinsic safety compliance for Russia per Gosgortechnadzor standards
contacts gold flashed