Control Panel in Class 1 Division 2 area

[Fireblade]

Hi

We are using an NEMA 4 control panel in a plant process area that until reasently had General Purpose Area Classification. The area will now get a Class 1 Division 2 hazardous area classification as new product will be made there. Does tha pane need to be explotion proof or is it sufficient to add explosion proof conduit seals to the conduit entries to the panel and a Z purge system?

Thanks

 

[cpal]

I don't think any type of pressurazation will allow the GP Enclosure to be installed in a classafied area.

I could be wrong and would be very interested to see a post that can explain it.

As I understand it I think the pressurazation only reduces the classification within the enclosure (will allow non-classified eq. inside) the hazardous atmosphere remains and the box it self needs to conform with with the Cl and Div it is installed in

 

[don_resqcapt19]

Charlie,
You can use a purge system with a box that is not explosion proof. There is no need for the box to be able to contain an explosion, because the purge system prevents the explosion. The following is from this document from one manufacturer of purge systems.

Pepperl+Fuchs' EPS System?s purpose is to allow the use of
general purpose or non-rated electrical or electronic devices,
with exception to devices which produce excessive heat,
utilize combustible gas, or expose arcing contacts to the
hazardous atmosphere, in Type 4 or 12 enclosures in the
place of explosion proof Type 7 enclosures. Other purposes
include heat, moisture and dust contamination prevention.

 

[cpal]

Charlie,
You can use a purge system with a box that is not explosion proof. There is no need for the box to be able to contain an explosion, because the purge system prevents the explosion. The following is from this document from one manufacturer of purge systems.

Thanks Don

as I mentioned I am very interested in opinions on these installations. I am somewhat weak in this area. The discription at the siet you posted mentions the following:

Model 3003 is designed to regulate and monitor pressure within
one or more sealed (protected) enclosures,

I question the phrase sealed protected enclosure???

 

[cpal]

Thanks again Don

I have read further and found 501.10(B) (4) and the explanatoy print in the HB.

 

[petersonra]

Hi

We are using an NEMA 4 control panel in a plant process area that until reasently had General Purpose Area Classification. The area will now get a Class 1 Division 2 hazardous area classification as new product will be made there. Does tha pane need to be explotion proof or is it sufficient to add explosion proof conduit seals to the conduit entries to the panel and a Z purge system?

Thanks

Yep.

One reason sealing is important is because air is horrendously expensive.

depending on what is in the box, you may not even need to pressurize/purge it.

 

[weressl]

Hi

We are using an NEMA 4 control panel in a plant process area that until reasently had General Purpose Area Classification. The area will now get a Class 1 Division 2 hazardous area classification as new product will be made there. Does tha pane need to be explotion proof or is it sufficient to add explosion proof conduit seals to the conduit entries to the panel and a Z purge system?

Thanks

NEMA 4 Type Z purge can house non-rated equipment in a ClassI, Division 2 area. You need to follow the requirements of the purge restrictions as described in NFPA 496. The box does not require XP connections, but the equipment connected to it may do. Conduit does require a seal, when it passes from one classification Division to another , such as 1, 2 and nonhazardous. You may wish to install additional sealing - such as silicone caulking - around the connections to your NEMA 4 box to prevent the loss of pressurizing media, eb it instrument grade air or nitrogen, since leaks to maintain the required pressure could be costly. (As it was pointed ouyt by others.)

 

[DWNorenProducts]

NEMA 4 purged control panels, class 1 div 2

NEMA 4 purged control panels, class 1 div 2

We work with these requirements a lot, supplying cooling solutions (heat exchangers) to panel shops. A NEMA 4 air/watertight panel with a purge allows the use of non-XP rated devices inside it. The NEMA 4 rating assures the purge will be contained (as pointed out, it's expensive!) but I think also the implication is the combustible atomosphere around the enclosure can't penetrate it and create a hazard. NEMA 7 is the higher, explosion proof construction spec that assures a fire/explosion will be contained by the enclosure. We and I'm sure other panel cooling providers offer units that throught the use of Class 1, Div 1 and 2 types of fans and blowers, can remove the heat from these control panels safely, whether it is a purged or non-purged design. Unfortunately, we only offer AC based designs, I'm searching for a 24v DC fan that would allow that option, so if anyone knows of such a 6" 230 CFM design, I'd sure appreciate it. That's what led me to this forum.

Doug

 

[bobgorno]

Hi

We are using an NEMA 4 control panel in a plant process area that until reasently had General Purpose Area Classification.

Since you call it a control panel, it brings up another question. What are you doing with your protruding devices, controls that are located on the panel surface? They are exposed to the hazardous environment and must be replaced or protected. A pushbutton is probably not an issue, anything else should be reviewed. Panel meters and single loop controllers are suspect. Pilot lights may or may not be OK.

Devices protruding thru the enclosure - Logically one wants to make them acceptable for the area classification that they are exposed to. If the enclosure is 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". The commentary goes on to mention pushbuttons and pilot lights being protected as long as their terminals are within the protected 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:
?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.

 

[Mkincy]

Control Panel in Class 1 Division 2 area

A purge panel should be acceptable in this situation. There will most likely need to be an alarm generated on the panel to indicate that the purge system has failed. While you are in Class 1 Division 2 which means it is unlikely to have a fault at the same time there is an explosive atmosphere. It is up to the supervising personel to shut the panel off in the case of a purge fail.

 

[bfmickl]

If your panel contains arching and sparking devices or if any of the components temps exceed the percentages, allowed by code, of the AIT of the gas or vapor requiring the hazardous classification, then a Z purge would be required on a nema 4 panel.
If you're installing a control panel, with terminals only, no fused TBs or knife type, and you have push-buttons, hand switches, pilot lights or other operator type devices installed, you can get by without the purge. All contacts on your operator devices would have to be of the hermetically sealed type. These are available thru companies such as Allen Bradley and most all of your high end control component suppliers.
As mentioned by others, conduit seals would be necessary where crossing boundaries such as between a general purpose area and the hazardous classified area.
You mentioned that this area carried a previous, general purpose, classification. Bear in mind, any existing equipment, that is now located in the hazardous classified area, must meet the code requirements for a CL 1, Div II area. Any exisiting conduits, that now enter this hazardous classified area, must be sealed within 10 ft of entering or exiting the boundary. Preferred seal location is on the non-hazardous rated side of the boundary. Bubbling around equipment can prove to be a way to avoid having to make major renovations. An engineering study should be performed, so as to have a clear picture as to your boundaries.
See NEC 501.105(B), 501.115(B)(1), 501.120(B) Further sealing requirements: 501.15(B)(2) and if you have the NEC handbook, see the Commentary Table 501.1

 

[rbalex]

When this thread first appeared, I was having medical issues that left me with the attention span of a 2 year old. Since many of the responses at the time were sound and practical for the issue at hand I just let my eyes glaze over and promptly forgot the whole issue. I normally try to avoid interfering with a thread when a solid response has already occurred anyway.

There were, in fact, several solid responses, but there also appears to be one misconception that I’d like to address and one oversight that I’d like to mention. This still doesn’t reduce the quality of the responses already in hand; they can be implemented practically as proposed with no negative affects other than excessive cost.

The misconception: See Section 501.15 (B)(2) Exception 3.
The oversight: See 501.15 (C) Exception as it applies to 501.15 (B)(2)

 

[petersonra]

Hi

We are using an NEMA 4 control panel in a plant process area that until reasently had General Purpose Area Classification. The area will now get a Class 1 Division 2 hazardous area classification as new product will be made there. Does tha pane need to be explotion proof or is it sufficient to add explosion proof conduit seals to the conduit entries to the panel and a Z purge system?

Thanks

Being as it is a division 2 area, it might not even need the purge system depending on just how the control system was constructed.

Many control components these days are rated for div 2. If any thing has hard contacts though, it is likely a purge system is the way to go.

 

[weressl]

When this thread first appeared, I was having medical issues that left me with the attention span of a 2 year old. Since many of the responses at the time were sound and practical for the issue at hand I just let my eyes glaze over and promptly forgot the whole issue. I normally try to avoid interfering with a thread when a solid response has already occurred anyway.

There were, in fact, several solid responses, but there also appears to be one misconception that I?d like to address and one oversight that I?d like to mention. This still doesn?t reduce the quality of the responses already in hand; they can be implemented practically as proposed with no negative affects other than excessive cost.

The misconception: See Section 501.15 (B)(2) Exception 3.
The oversight: See 501.15 (C) Exception as it applies to 501.15 (B)(2)

So the practical result of this would be that an explosion in a Div. 1 or 2 location would be allowed to be propagate/relieve into a less-hazardous or non-hazardous area? Or am I missing something?

 

[rbalex]

So the practical result of this would be that an explosion in a Div. 1 or 2 location would be allowed to be propagate/relieve into a less-hazardous or non-hazardous area? Or am I missing something?

Not at all; remember the OP was a Division 2 application, and Sections 501.15 (B)(2), Exception 3 and 501.15 (C) Exception only apply to Division 2, in this particular case. (501.15 (C) Exception may also apply to intrinsically safe applications)

Sections 501.15 (B)(2), Exception 3 permits omitting boundary seals for enclosures or rooms that are unclassified by virtue of pressurization. As noted by others this may still be costly because of the additional air that may be necessary to maintain proper pressure; however, 501.13(C) Exception recognizes the seal is not required to be explosionproof; as does the last sentence in the main part of 501.15 (B)(2).

As always, if a Division 1 location is somehow associated with the installation, then sealing appropriate to those conditions is necessary.

 

[weressl]

Not at all; remember the OP was a Division 2 application, and Sections 501.15 (B)(2), Exception 3 and 501.15 (C) Exception only apply to Division 2, in this particular case. (501.15 (C) Exception may also apply to intrinsically safe applications)

Sections 501.15 (B)(2), Exception 3 permits omitting boundary seals for enclosures or rooms that are unclassified by virtue of pressurization. As noted by others this may still be costly because of the additional air that may be necessary to maintain proper pressure; however, 501.13(C) Exception recognizes the seal is not required to be explosionproof; as does the last sentence in the main part of 501.15 (B)(2).

As always, if a Division 1 location is somehow associated with the installation, then sealing appropriate to those conditions is necessary.

So a conduit entering from a Div. 1 location into a pressurized enclosure would need to be XP sealed? The conduit only contains power wires.

 

[rbalex]

So a conduit entering from a Div. 1 location into a pressurized enclosure would need to be XP sealed? The conduit only contains power wires.

Under the original conditions of the OP and the additional condition you now specified, a Division 1 boundary seal is required by 501.15(A)(4). Neither of the Execeptions apply. Oddly enough though, if the pressurized enclosure were in Division 1 and the pressurization sscheme were designed to include the conduit system, 501.15(A)(2) would also permit ommitting the enclosure seal. Note 501.15(A)(4) doesn't specify the enclosure NEMA Type and a bounday seal still may be necessary somewhere. Under the general theory that what is permitted in Division 1 is also permitted in Division 2[501.10(B)(1)(1)], it may also apply to the OP.

 

[weressl]

Under the original conditions of the OP and the additional condition you now specified, a Division 1 boundary seal is required by 501.15(A)(4). Neither of the Execeptions apply. Oddly enough though, if the pressurized enclosure were in Division 1 and the pressurization sscheme were designed to include the conduit system, 501.15(A)(2) would also permit ommitting the enclosure seal. Note 501.15(A)(4) doesn't specify the enclosure NEMA Type and a bounday seal still may be necessary somewhere. Under the general theory that what is permitted in Division 1 is also permitted in Division 2[501.10(B)(1)(1)], it may also apply to the OP.

I know that I have stepped beyond the OP with my question.

My concern was that simple conduit carying power wiring leaves a purged enclosure in Div. 1 area does not require an XP seal until it reaches a device that requires and XP seal. An electrical failure inside the conduit would ignite an explosion that in turn would overcome the non-XP seal and vent into the purged eclosure AND that in trun would vent into the Div. 1 surroundings.

Isn't this what the Code seem to allows to happen?

 

[rbalex]

I know that I have stepped beyond the OP with my question.

My concern was that simple conduit carying power wiring leaves a purged enclosure in Div. 1 area does not require an XP seal until it reaches a device that requires and XP seal. An electrical failure inside the conduit would ignite an explosion that in turn would overcome the non-XP seal and vent into the purged eclosure AND that in trun would vent into the Div. 1 surroundings.

Isn't this what the Code seem to allows to happen?

LOL. We're actually approaching same wavelength Laszlo. I'm opposed to non-xp seals in general. You can't find my tirade against them any longer because it was in the "Archives."

It's still important to remember that somewhere between the purged Division 1 enclosure (with no seal) and an enclosure that might permit a non-xp seal is a boundary that will still require an xp seal. Now in theory it may be the same seal fitting, but xp trumps non-xp because both sets of requirements must still be met.