Process seals?

[greenspark1]

I'm looking at article 501.17 for the first time which requires process seals for applications with pressure or temperature. I have both in a job and am trying to figure out if the ABB instruments we're using need a process seal or not. There is no clear language on the instrumentation data sheets and 501.17 isn't very clear exactly what it's looking for. Of course instruments are sealed to keep out the gas it's measuring, but how much sealing is required to avoid a process seal? Any experience/advice?

 

[rbalex]

I'm looking at article 501.17 for the first time which requires process seals for applications with pressure or temperature. I have both in a job and am trying to figure out if the ABB instruments we're using need a process seal or not. There is no clear language on the instrumentation data sheets and 501.17 isn't very clear exactly what it's looking for. Of course instruments are sealed to keep out the gas it's measuring, but how much sealing is required to avoid a process seal? Any experience/advice?

I have plenty of experience.

I think you may be over analyzing a bit. The purpose of a process seal is pretty straight forward:

...
A process seal is a device to prevent the migration of process fluids from the designed containment into the external electrical system. Process connected electrical equipment that incorporates a single process seal, such as a single compression seal, diaphragm, or tube to prevent flammable or combustible fluids from entering a conduit or cable system capable of transmitting fluids, shall be provided with an additional means to mitigate a single process seal failure.

If the ABB equipment isn't clearly marked, it isn't suitable.

...
Process-connected electrical equipment that does not rely on a single process seal or is listed and marked ?single seal? or ?dual seal? shall not be required to be provided with an additional means of sealing.

I.e., if the equipment isn't properly marked, an additional means [501.17(1)-(3)] between the device and the electrical wiring method is required.

 

[greenspark1]

I hope I'm over analyzing.
Here is the pressure transmitter we're using:
http://www.abb.us/product/seitp330/...2c005034c9.aspx?productLanguage=us&country=US

and the temperature transmitter:
http://www.abb.us/product/seitp330/29c79692e5466498c125713f005ab751.aspx

I don't see that they clearly meets the NEC requirements where it doesn't require additional sealing.

 

[rbalex]

I don't plan to do the rest of the homework for you but I note the temperature transmitter data sheet doesn't appear to indicate a direct connection to process equipment, so Section 501.17 is moot.

The pressure transmitter data sheet tells a different story and makes no clear statement about process seals. It would appear that Section 501.17 would apply and barring a clear marking on the enclosure itself that one of the alternate methods 501.17(1)-(3) is required.

 

[don_resqcapt19]

Bob,
Is the fact that most pressure transmitters use a fluid between the process and the pressure transducer enough to eliminate the need for a separate process seal?.

 

[rbalex]

Bob,
Is the fact that most pressure transmitters use a fluid between the process and the pressure transducer enough to eliminate the need for a separate process seal?.

Usually; however, the ability to avoid a Section 501.17 condition is a big deal and, if it has a feature to avoid it, it's usally a significant sales, marketing "bullet".