Class 1 div 2 Equipment - UL/FM Listed but Protection Technique Isn't Given

Location
Michgian
Occupation
Engineer
Per Article 500.7 - Electrical and Electronic Equipment in Hazardous (classified) locations shall be protected by one of more of the techniques in 500.7(A) through (P)

The issue that I have is that I see lots of equipment that is listed as such-

UL (Listed)
Class I, Div 2, Group A, B, C, D Class I, Zone 2, IIC T4
Class II, Zone 22 IP66

When asking the vendor what protection technique is used- I never get a clear answer and just get wiring instruments such as-

The hazardous locations classes, groups and division as described under products covered.
2. WARNING – EXPLOSION HAZARD – Do not disconnect equipment unless power has been removed or the area is known to be non-hazardous.
3. WARNING – EXPLOSION HAZARD - Substitution of any components may impair suitability for Class I, Division 2.
4. To maintain type 4X/IP66 rating zero screw must be installed.

The issue with this is it doesn't tell me if this is NI/IS which require entity parameters to complete the NI/IS circuit or if it's Explosion proof and therefore requires an Explosion proof seal. Do I assume that this equipment uses a different technique and just treat it as a magically rated black box?
 

Jimmy B

Member
Location
Canada
Occupation
Electrician/Technologist
Does it look bomb proof? If not, then it's probably not explosion proof! :LOL:

In all seriousness (although I would say the test above would pass the common sense test a lot of the time!), is it just an enclosure and you are installing the parts inside, or is it a fully provided vendor package? More info is needed to answer the question, but I'm sure that by getting some part numbers, etc you could get some answers. Can you provide part numbers/info?
 
Location
Michgian
Occupation
Engineer
This particular piece of equipment is a Brooks Mass flow Controller-


I know this isn't explosion proof, and I don't think it is NI or IS either.

I also don't think this piece of equipment falls in under any special allowances under 500.(C)(6)
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
You need to reread the Section 500.7 introductory text. It does NOT require that a device’s protection technique be identified. It simply says that Subsections 500.7(A) through (L) indicate the acceptable protection techniques. The Subsections also indicate the locations where each protection technique is acceptable.

From the link you attached, “Elastomer Sealed“ would indicate Subsection 500.7(J) Hermetically Sealed.

Subsection 500.8(C) indicates what marks are required to identify hazardous location equipment. Note that the protection technique is not required to be identified. Subsection 500.8(C)(6) indicates several cases where no hazardous location marks are required at all. Subsections 500.8(C)(6)(c) & (d) indicate most IS and NI devices will not be marked. This is because they must be installed per a control drawing and/or general wiring methods are already acceptable.
 
Location
Michgian
Occupation
Engineer
Per Article 100 of NEC

Hermetically Sealed- Equipment sealed against the entrance of an external atmosphere where the seal is made by fusion, for example, soldering, brazing, welding, or the fusion of glass to metal.

I don't believe Elastomer Sealed would meet this definition.

The vendor is now telling me that this Device is Non incendive.

As you mentioned, the NEC requires NI circuits to be installed per control drawings.

From ASI-12.12.01-2015 (I don’t have a copy of 2013) section 3.3 states-

control drawing-
a drawing or other document provided by the manufacturer of the nonincendive field wiring
apparatus or the associated nonincendive field wiring apparatus that details the allowed
interconnections with other circuits or equipment. The control drawing includes the applicable
electrical parameters to permit selection of equipment for interconnection.

The vendor is stating these electrical parameters are not required. My understanding that these are required because this instrument will be connected to an associated nonincendive field wiring apparatus (In my case, this is our controller that will be located in a standard area)
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Per Article 100 of NEC

Hermetically Sealed- Equipment sealed against the entrance of an external atmosphere where the seal is made by fusion, for example, soldering, brazing, welding, or the fusion of glass to metal.

I don't believe Elastomer Sealed would meet this definition.

The vendor is now telling me that this Device is Non incendive.

As you mentioned, the NEC requires NI circuits to be installed per control drawings.

From ASI-12.12.01-2015 (I don’t have a copy of 2013) section 3.3 states-

control drawing-
a drawing or other document provided by the manufacturer of the nonincendive field wiring
apparatus or the associated nonincendive field wiring apparatus that details the allowed
interconnections with other circuits or equipment. The control drawing includes the applicable
electrical parameters to permit selection of equipment for interconnection.

The vendor is stating these electrical parameters are not required. My understanding that these are required because this instrument will be connected to an associated nonincendive field wiring apparatus (In my case, this is our controller that will be located in a standard area)
It is not like the "control drawing" has to have a label that says "control drawing" on it.

Electrical parameters are things like what voltage can be applied. I have never seen any electrical part that does not have this type of information in the instruction manual.
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
Per Article 100 of NEC

Hermetically Sealed- Equipment sealed against the entrance of an external atmosphere where the seal is made by fusion, for example, soldering, brazing, welding, or the fusion of glass to metal.

I don't believe Elastomer Sealed would meet this definition.

The vendor is now telling me that this Device is Non incendive.

As you mentioned, the NEC requires NI circuits to be installed per control drawings.

From ASI-12.12.01-2015 (I don’t have a copy of 2013) section 3.3 states-

control drawing-
a drawing or other document provided by the manufacturer of the nonincendive field wiring
apparatus or the associated nonincendive field wiring apparatus that details the allowed
interconnections with other circuits or equipment. The control drawing includes the applicable
electrical parameters to permit selection of equipment for interconnection.

The vendor is stating these electrical parameters are not required. My understanding that these are required because this instrument will be connected to an associated nonincendive field wiring apparatus (In my case, this is our controller that will be located in a standard area)
I’m going to suggest you read the last sentence of Section 90.1(A).

The examples in the definition of Hermetically Sealed are not exhaustive. The key is the opening statement,”Equipment sealed against the entrance of an external atmosphere where the seal is made by fusion…” In this case “fusion” is in the sense of:
2: a union by or as if by melting: such as
a: a merging of diverse, distinct, or separate elements into a unified whole
[From Meriam-Webster 11th Collegiate Dictionary (the “official” NFPA dictionary for definitions not included in the Standard itself)]; i.e., hermetically sealed excludes the entrance of voliatiles by some means, in this case, elastomers.

Fundamentally, NI installtions beyond the barriers can be General Purpose (”Ordinary Locations” per UL parlance). See Section 501.10(B)(3).

Of course, you don’t have to accept my interpretations even though I have been designing hazardous location installations for over 50 years.
 
Location
Michgian
Occupation
Engineer
I’m going to suggest you read the last sentence of Section 90.1(A).

The examples in the definition of Hermetically Sealed are not exhaustive. The key is the opening statement, ”Equipment sealed against the entrance of an external atmosphere where the seal is made by fusion…” In this case “fusion” is in the sense of:

[From Meriam-Webster 11th Collegiate Dictionary (the “official” NFPA dictionary for definitions not included in the Standard itself)]; i.e., hermetically sealed excludes the entrance of voliatiles by some means, in this case, elastomers.

Fundamentally, NI installtions beyond the barriers can be General Purpose (”Ordinary Locations” per UL parlance). See Section 501.10(B)(3).

Of course, you don’t have to accept my interpretations even though I have been designing hazardous location installations for over 50 years.


Hi Bob, I understand the NEC code is not intended as a design specification or instruction manual, but I am just trying to wrap my head around what is allowed and what is not.

I have torn apart a few devices that were hermetically sealed such as pepperl and fuchs barriers and Allen Bradley hermetically sealed switches and I have found that these devices are completely sealed in a very hard epoxy type material. If devices can get approved with just an elastomer seal, that method would be much easier. Also, I would really love to find hermetically sealed enclosures so I can avoid using purged enclosure for non-rated equipment in Class I Div 2 Areas.

It would be much easier for manufacturers to throw some rubber seals on their devices and send them to UL for approval for Class I Div 2 approval than it would be messing around with the requirements associated with designing equipment to be nonincendive.
 
Location
Michgian
Occupation
Engineer
I have always assumed that if it does not list a particular parameter that it does not matter for that particular device.

At some point I just need to take the manufacturer at their word as longs as I follow their installation instructions for the area that I should be covered. It is the curious engineer in me that really wants to know how this device meets area classification with such simplistic instructions and others devices from other manufactures require all the entity parameters to be met.

I don't think the people at Brooks actually knows how this meets area classification. Maybe they worked with another company to get this thing rated and UL listed for Brooks.

If I was to guess,

1) this device has an internal barrier (that is hermetically sealed) that limits power to the internal circuitry from the input power and therefore is both hermetically sealed and nonincendive

or

2) Maybe it is as simple as there are no arcing devices inside the device at all. capacitors, FETs, resistors diodes and inductors are typically non arcing under normal circumstances.
 
Location
Michgian
Occupation
Engineer
My colleague received the following response from Brooks-

"Nonincendive equipment is required to be wired using the methods defined in NEC 70, 501.10(B)(1)/(2) as these wiring methods provide a degree of physical protection to the wiring, and no faults in the wiring are considered likely.

There is another permitted method as per 501.10(B)(3). Nonincendive field wiring provides an alternative wiring method based on limitation of energy in the wiring during possible wiring faults, similar to intrinsic safety wiring, but specifically limited to Division 2. This wiring method is generally limited to low-power apparatus. This method requires users to use an associated nonincendive field wiring apparatus (power supply). The installation has to be done per a control drawing.

The Brooks SLA5800/SLAMF device cannot use this alternate wiring method. We do not have a control drawing or entity parameters for the barrier. You will have to provide a physical protection to the wiring per code.

Attached is the UL report for SLAMF, the report list all the marking & installation requirements.

The cert is based on “non-arcing circuits” as per UL 121201, NONINCENDIVE ELECTRICAL EQUIPMENT FOR USE IN CLASS I AND II, DIVISION 2 AND CLASS III, DIVISIONS 1 AND 2 HAZARDOUS (CLASSIFIED)LOCATIONS- Edition 9

‘Non-incendive’ circuits, which carry only low levels of voltage and current because they are ‘energy-limited’ within the field circuit. These circuits can be live-worked in a similar way to intrinsically safe circuits.

‘Non-arcing’ circuits, which carry high levels of voltage and current, and which must not be live-worked in the hazardous area. Their safety is ensured by not allowing arcs or sparks to be produced, usually by means of mechanical protection of wiring and by eliminating unprotected contacts."


So this is considered a "Non-arcing" circuit and not actually Nonincendive. This explains a lot!
 
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