Nonincendive transmitters
Nonincendive transmitters
(OP)
I am working on a design in a Class 1 Div 2 hazardous location. Have 10 Yokogawa pressure transmitters, 24 VDC supplied, loop powered, wired to an AB Contrologix PLC. The transmitter model I selected is rated as nonincendive (NI)for Class 1 Div 2 and intrinsically safe (IS)for Class 1 Div 1. Customer wants me to use an explosionproof transmitter, arguing that my loop diagrams do not show any NI or IS wiring, which is true. How do I show NI wiring in a loop diagram? How do I argue against the explosion proof request?
How do I wire the transmitters in order to conform to the nonincendive rating? According to NEC 501.4(B)(3), I can use wiring methods allowable in non-hazardous locations.
How do I wire the transmitters in order to conform to the nonincendive rating? According to NEC 501.4(B)(3), I can use wiring methods allowable in non-hazardous locations.





RE: Nonincendive transmitters
Here's s starting point: have you got a correctly specified IS barrier in the loop? Check out MTL's web site for some useful information, also Pepperl & Fuchs is worth a look.
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If we learn from our mistakes I'm getting a great education!
RE: Nonincendive transmitters
It would be a rare combination of equipment and products where the normal operating temperature of a transmitter would exceed 80% of the auto ignition temperature of the flammable product.
RE: Nonincendive transmitters
RE: Nonincendive transmitters
A device which is rated Class 1 Div 2 NONINCENDIVE by an approved testing laboratory is suitable for use in a Class 1 Div 2 area classification. It does not require the use of an XP enclosure and poured seal, or zener barrier and IS wiring (intrinsic safety methods for Div 1 areas.
Some clients have standards which require that seals be installed and poured on all devices with an explosion-proof housing, REGARDLESS of whether or not the device is ALSO rated Div 2 nonincendive. The idea is that some devices are rendered suitable for Div 2 areas SOLELY by means of explosion proofing (ie. the devices themselves are NOT rated as non-incendive for Div 2). Pouring the seal removes the risk. And it's a nice, simple rule that their electricians can understand: if it's in an XP box, you pour a seal- always.
By the same logic, some clients require that any device which is rendered IS by the use of a barrier, be installed with a barrier and IS wiring regardless of whether or not the device is ALSO rated as nonincendive for Div 2 (ie. WITHOUT a barrier).
You didn't mention which code you are designing under, but these "belt and suspenders" client standards go above and beyond the requirements of NEC (NFPA 70. Customers are of course free to specify anything they want which goes beyond code- as long as they pay for it.
RE: Nonincendive transmitters
Thank you for your tip. I am designing by NEC (NFPA 70), but I also found an FM approval standard 3611, which specifies calculations that have to be run in order to approve the entire system (transmitter+wiring) as nonincendive. I am going through it right now.
RE: Nonincendive transmitters
Russell White, P.E.
Automation Technologies, Inc.
www.AutomationNC.com
Automation Help
www.PLCMentor.com
RE: Nonincendive transmitters
Does the loop drawing show an energy limited analog input module selected for the AB Contrologix PLC? Does such I/O exist? If I touch a tool across the transmitter leads the energy level must be below the level that could ignite a source. Non incindive is like intrinsic safety less the redundancy etc.
Wiring per se, a.k.a. the conductors are neither hazardous nor non hazardous. The energy must be limited; or contained.
How does rauval show NI wiring; or wire the transmitter? Show the energy limiter.
How does he argue against the explosion proof requist? I would not argue but agree to comply. However demonstrate that the loop is compliant. The NI transmitter itself does not comply.
If all of this is wrong then I don't understand NI wiring requirements. I don't use NI wiring devices. I prefer explosion proof practices. The transmitter is likely available compliant with IS, NI and explosion proof practices.
Regardless of the system assure that nothing within the design would cause a disaster.
RE: Nonincendive transmitters
Russell White, P.E.
Automation Technologies, Inc.
www.AutomationNC.com
Automation Help
www.PLCMentor.com
RE: Nonincendive transmitters
Just because the device is NI doesn't mean the wires running to it can't be compromised and deliver ignition energy.
What am I missing here? Is this because it's Div2 as compared to Div1?
Keith Cress
kcress - http://www.flaminsystems.com
RE: Nonincendive transmitters
If you are carful with your component selection, you can have a non purged I/O or control panel in a c1,D2 area. Usually relays are the hardest component to get compliant, but there are relays with hermetically sealed contacts.
Russell
Russell White, P.E.
Automation Technologies, Inc.
www.AutomationNC.com
Automation Help
www.PLCMentor.com
RE: Nonincendive transmitters
Keith Cress
kcress - http://www.flaminsystems.com
RE: Nonincendive transmitters
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If we learn from our mistakes I'm getting a great education!
RE: Nonincendive transmitters