Temperature Indication/Recording in Class 2, Div 2, Group G Area

[Doggert]

I have an issue where I need a quick way to set-up some temperature logging on a process that exists in a Class 2, Div 2, Group G environment.

I need to measure and record temperature within a powder process from the discharge of a cooling vessel to the packaging area. All of the equipment in this line will contain mainly powder/granular calcium stearate.

I only need the data to record for approximately 1 week or so, and then I will analyze the data for temperaturs of the material as it moves through these areas.

My question is this: Since this is a Class 2, Div 2 area, can I use something like this:

http://www.omega.com/ppt/pptsc.asp?ref=HH309&Nav=dase01

And put it in a NEMA 4x enclosure. I could then draw the thermocouple wires out and put them in the pieces of equipment I need readings in.

I'm thinking I would need maybe 1 or 2 of these loggers to get what I need.

Is there a problem with doing that? Can you put a device like this in a NEMA 4x enclosure + have it be usable in a Cl 2, Div 2 environment? Are thermocouples any kind of problem at all in a Cl 2, Div 2 environment?

Pardon my ignorance in this - I'm not an electrical guy. I'm just a ChE that needs quick, recorded temperature data.

 

[Doggert]

Actually, I've moved on with this project and have come up with a new issue.

Again, I apologize for my lack of electrical knowledge:

I've found a company that supplies intrinsically safe thermocouple data loggers, and they're actually cheaper than the previous company.

Now my question is with the thermocouple sensors themselves. I need to use a K type, either beaded or with a probe. This sensor will be placed directly in the path of the material as it is processed (that's the point, actually), thus it will be in a Class 2 Div 1 environment (being inside the equipment).

The data logger is rated for this environment (even though it's going to be outside the equipment), but do I need to worry about the thermocouple probe itself. I know they work by the 2 disimilar metals creating a voltage on the millivolt scale, but is this something that needs to be hazardous classified - or is the logger the only thing that needs to be that way?

The reason I'm confused is that I've seen a lot of information on hazardous classified loggers/transmitters, but they rarely seem to mention the probes themselves.

I need to know that if I use this intrinsically safe logger with any type of thermocouple, will the entire system still be safe for this environment?

 

[itsmoked]

No you do not need to worry about T/Cs. They cannot generate anywhere near enough energy to even light a hot fart in perfect stoichiometric balance.

Normally you can run any dang T/C monitor/logger/PC/laptop/whatever for the logging function.

Then you place something called an "Intrinsic Safety Barrier" in the the lines between the "logger" and the sensor. The logger can explode weekly, if it desires, because it must be located outside of the hazardous area. The Safety barriers are also outside the hazardous area but located near the area boundary. All the sensors heading into the hazardous area must pass through the proper approved barriers and those wires must remain separate from any other wires.

The barriers guarantee that the energy let thru to the hazardous area is ALWAYS less than that required to cause ignition.

T/Cs are the easiest thing to barrier because they only pass uVolts and uAmps.

Now if you have a particular instrument that is classified as being able to operate in a properly rated hazardous area then it has been designed and tested to confirm that more than two mechanical/electrical faults must occur in just a certain way for the device to become hazardous and you should need no other external gizmos to maintain protection especially with T/Cs.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Doggert]

Keith,

Thank you for the detailed response.

I've gone ahead and ordered what I need.

Thanks again