Intrinsic Safety in Class 1 Div 1

[BZ2005]

Am I able to run intrinsic safety cabling of type (PLTC ?standard? tray cable) through a Class one Division 1 area?
The intrinsically safe circuit will run basically run from a properly purged panel out a seal to a pass trough rigid conduit to a class 1 div 1 rated intrinsic device. The entire system will be in a class one div 1 area with no explosion-proof fittings or seals
Is this legal?

 

[weressl]

Am I able to run intrinsic safety cabling of type (PLTC ?standard? tray cable) through a Class one Division 1 area?
The intrinsically safe circuit will run basically run from a properly purged panel out a seal to a pass trough rigid conduit to a class 1 div 1 rated intrinsic device. The entire system will be in a class one div 1 area with no explosion-proof fittings or seals
Is this legal?

After leaving the purged box and sealing the IS cable with a CGB type fitting, only to prevent the purge leak, any wiring method acceptable for ordinary installation of the PLTC cable is acceptable. You need to keep this wiwirn separate from others due to the IS requirements, eg. can't run it together with other control wiring.

 

[BZ2005]

I am now are %100 sure that I can run PLTC cable in class 1 div 1 area if the circuit is Intrinsically Safe.

But the CGB style cord grips are not Class 1 div 1 rated coming out of my "X" purged panel. Wouldn't the fitting on the purged panel and at the devices (ASCO solenoid's) have to be class 1 div 1 rated?
The device has to be.

NOTE:
As you are aware the panel has non-IS items enclosed.

 

[weressl]

I am now are %100 sure that I can run PLTC cable in class 1 div 1 area if the circuit is Intrinsically Safe.

But the CGB style cord grips are not Class 1 div 1 rated coming out of my "X" purged panel. Wouldn't the fitting on the purged panel and at the devices (ASCO solenoid's) have to be class 1 div 1 rated?
The device has to be.

NOTE:
As you are aware the panel has non-IS items enclosed.

Try to define a little more precisely your questions, please.

I am assuming that the ASCO solenoids are the IS field devices. They do need to be IS rated. IS installation components could be any devices that are approved for non-hazardous installation of the specific wiring system you choose to use.

Since you are only trying to contain the purge pressure in the X-purge box, any fitting that is approved for non-hazardous locations and fulfills the pressure containment requirement is acceptable. (BTW using a fitting that minimizes pressure loss is an engineering, or installation recommendation, not an NEC requirement.)

The panel may contain IS and non-IS items, provided that the IS items or the IS side of IS barriers are segregated from the non-IS items. Components that are purely IS, eg. either devices that are powered by IS barriers or signal generators that are connected to IS barriers would not need to be in the enclosure.

 

[BZ2005]

Sorry, for not being totally clear.
I have read this section of the NEC Like 5 times and am just trying to grasp the finer points of installing / application.

Regarding the cord grips on to an IS device in a classified area...
Do they have to be explosion proof?
If the device is "Intrinsically Safe" along with circuit...

In a X-purged box within a class 1 div 1 area
Do panel door mounted switches and door mounted PLC Interface screens need to be need to be explosion proof?
These are not Intrinsically safe devices. I know at least they would have to hold the pressure.

Thanks

 

[weressl]

Sorry, for not being totally clear.
I have read this section of the NEC Like 5 times and am just trying to grasp the finer points of installing / application.

Regarding the cord grips on to an IS device in a classified area...
Do they have to be explosion proof?
If the device is "Intrinsically Safe" along with circuit...

In a X-purged box within a class 1 div 1 area
Do panel door mounted switches and door mounted PLC Interface screens need to be need to be explosion proof?
These are not Intrinsically safe devices. I know at least they would have to hold the pressure.

Thanks

'Cord grips' and Intrinsic Safety have nothing to do with each other. The grip does not significantly change the circuit parameters of the IS circuit.

In a purged panel thel door mounted devices do not have to have any XP rating, the Code reamins silent on that issue AFAIK. Although some argue that external surface temperature should be taken into consideration. Some of the answers to that I've heard that if the device exceeds the AIT temperature of ANY material then that should have been protected from human exposure. The other argument is that there is no restriction by the Code that the purged enclosure temperature - due to internal components that raise its temperature above ambient - should be investigated or verified, or that removal of the heat should be engineered.

Indeed, not only that they do need to hold the pressure, but you have to assure that if you employ membrane panels/switches they can withstand the pressure differential.

 

[bobgorno]

For purged enclosures in a Div. 2 area no seals are required at the enclosure/boundary - 501.15(B)(2), Exception #3.

However, in a Div. 1 area, a seal is required, 501.15(A)(2). Note, there is no exception that allow these seals to be non-XP. I'm sure someday there will be. It makes no sense to have an XP seal on a sheet metal can.

Devices protruding thru the enclosure - Logically one wants to make them acceptable for the area classification that they are exposed to. If the enclosure in unclassified inside, the enclosure wall is the boundary and the area outside of it is hazardous. There is no magic force field that envleopes the protruding devices.

Review the commentary in the NEC Handbook following 500.7(D). Key words "within the enclosure"

Review the definitions in NFPA 496 for pressurization types. Key words "within the protected enclosure?

The following are excerpts from ISA-RP12.4-1996 (Note this is outdated and I recommend purchasing the newer version):
?Chapter 6 - Components that protrude through the enclosure? ?Components should permit the flow of the protective gas to properly purge and pressurize the component. (Additional information is located in Annex B.) Exception: components that are suitable for the hazardous location that would exist in the absence of the protective gas do not require purging or pressurization? ?Annex B, 6 ? This requirement is intended for components such as switches, keyboards, lamps, indicators, and for mechanical devices such as shafts that penetrate the enclosure. Methods of protection to comply with the exception include mounting the component in an explosion proof housing or using the component in an intrinsically safe circuit??

From P&F BEBCO EPS, Purging Technology Review:
The use of devices that penetrate the surface of a protected
enclosure must be carefully scrutinized. Protruding devices
will likely contain electrical components that could either be
exposed to the hazardous location or be isolated from the
fl ow of protective gas. Conventional wisdom suggests that a
protruding device should be acceptable if it is (1) explosion
proof, (2) intrinsically safe, (3) proven to emit insufficient energy
to ignite the surrounding atmosphere (applicable for Division 2
locations only), (4) constructed so that all electronics within its
face are suitably sealed from the surrounding environment and
properly ventilated to the protected enclosure, or (5) isolated
from the surrounding atmosphere by a sealed window or access
door that is properly ventilated to the protected enclosure.
Controllers, Indicators & Recorders
Today's panel mounted instrumentation is almost strictly
electronic. The protruding face of these instruments normally
contains LEDs, LCDs and incandescent or fl orescent lights.
Therefore, it is extremely important to isolate all instrumentation
from the surrounding atmosphere, unless the face is sealed
and all electronics are properly ventilated to the protected
enclosure.

 

[BZ2005]

Alright let me get this straight, I Have a properly purged panel that contains both "IS" and standard wiring correctly separated I can / have to:

1.)Use seal fittings on the "IS" wiring running out of my Panel; no other real protection after that because it's "is"

2.)Use seal fitting on the standard wiring running out of my panel; rigid conduit and other seals later down the line

3.) Non "IS" Switches and other Interfaces that stick out the face of the panel; must be explosion proof

 

[weressl]

Alright let me get this straight, I Have a properly purged panel that contains both "IS" and standard wiring correctly separated I can / have to:

1.)Use seal fittings on the "IS" wiring running out of my Panel; no other real protection after that because it's "is"

2.)Use seal fitting on the standard wiring running out of my panel; rigid conduit and other seals later down the line

3.) Non "IS" Switches and other Interfaces that stick out the face of the panel; must be explosion proof

1.) You use the seal only to contain the purge pressurization, so the seal does not have to be an XP seal fitting. Any approved wiring fitting that is relatively pressure tight will fulfill the need. This is not an electrical requirement, only a practical design consideration so that you don't have to supply the extra air that is lost through a non-sealing fitting.

2.) Again, you have to maintain thr purging pressure in the enclosure BUT your non-IS conduit has to withstand the potential explosion pressure from the on-pressurized side and not allow the propagation of flames into the area that is rendered non-hazardous by pressurization. eg. the inside of your purged box.

3.) If a device does not contain a heating element - ex. incandescent filament -, and it is expected to provide a reasonable purge seal, there is no reason why all heating or spark producing parts of it could not be viewed at to be INSIDE of the purged enclosure, therefore no different consideration is to be given to them than components mounted entirey within the enclosure.