Sealoff Fittings in Division 2 Areas

mrxphil,

Take a look at 501.15 (B) (1) "In Class 1, Division 2 locations, a seal is required in each conduit entering an enclosure that is required to be explosionproof, in order to complete the explosionproof enclosure".

My interpretation is nothing to do with staying in same environment but more an issue of maintaining the CL1, Div2 rating of the enclosure.

I interpret this as a seal-off is required.

Just curious, were did you find NEMA 4 and NEMA 12 panels that are labeled for Class 1 - Div 2?

Shouldn't these be NEMA 7 or NEMA 9 to be CL1, Div2 rated?

Have a look at 501.15 (A) (1) (1) The enclosures contain "apperatus" correct?

KJK/USA: Appreciate your reply. Actually, the enclosures are listed and labeled for Div 2 atmospheres. Check out the nameplate photo below. Using 501.15 (E), since all the cables are gas tight jacketed and since the enclosures are not required to be explosion-proof, as they would be in a Class 1, Division 1 area, it seems to me that sealoffs are not required. I still would like to hear the thoughts of others on here, though. I don't pretend to be the electrical genius of the world and can always learn something new. Let me have your thoughts.

Thanks for the photo.

Are you running conduit systems with myers hubs or cable systems with sealing glands to the control panel?

Are there terminal strips and/or arcing/sparking apparatus (relays/contactors/fuses) in the control panel?

Just some questions for thought.

Like you I will wait to hear others opinions/interpretations.

Regards KJK

We are using open-ended RGS conduit at cable tray connections below the open grating deck for all wiring and the tray goes out of the classified building to the outdoors, so there is no transmission hazard. The interior of the panels in question contain only devices that are listed and labeled for Class 1, Division 2, Group D, so they are not sources of ignition at all.

--------------------
ANSI/ISA-12.01.01-1999
Definitions and Information Pertaining to Electrical Apparatus in Hazardous (Classified) Locations

5.2.4 Sealing (sealed device)
Sealing is a technique primarily applicable to Division 2 classified areas. The basic principle provides for the isolation of electrical components within an enclosure by sealing the enclosure well enough to prevent the casual entrance of any external flammable atmosphere. Sealing may be accomplished by several means, from simple gasketing to a glass-to-metal hermetic seal. Reference ISA-S12.12, IEC 60079-15, and CEC 22.2, No. 213, for further information.

A hermetic seal is considered effective enough to be insensitive to gas group, but a gasketed enclosure is sensitive to particular gases/vapors (based on their diffusion constants and on the effectiveness of the gasket seal). For example, hydrogen, with its small molecular structure, will diffuse much more easily than the heavier hydrocarbons.

The sealing technique has been applied in Europe to a variety of process control equipment. In North
America, hermetically sealed components such as relays, push button contacts, and limit, level, and
pressure switches are commonly used.

The following are two levels of protection provided by sealing: (1) the enclosure is sealed, and (2) application is restricted to areas that become hazardous only upon equipment or process failure (Division 2)
-------------------------

Caveat - this standard is dated 1999, there might have been an update in the interim.

The middle two paragraphs are intended for devices like the housing of a microswitch, which is hermetically sealed for Div 2 service.

I read the first and last paragraphs as requiring an enclosure to be sealed from the 'casual' intrusion of gas in the event of a fault. If the cabling entrances are sealed by design, then seal-offs become redundant.

I find the NEC quote confusing, because I don't think of non-incendive CL 1, Div 2 as explosion proof. It's rated for non-incendive devices. In fact, section 4.2.2 elaborates on the Div 2 concept, which was adopted first in the US and then migrated overseas.

To me the approach taken by you seems a bit confusing, your are refering to hazard area zoning while you are actually concerned with explosion proof catagory like EEx'd.

Further you are saying that a dedicated ventillation system is there, refereing to applicable codes an adequately ventilated space shall be classified as Div II instaed of Div I and a Div II goes non-classified etc.

Natural gas is in the catagory of lighter than air etc.

So what actually you are asking for and in what context ?

mountk2: We have made the atmosphere around these NEMA 4 panels in this building Class 1, Division 2, by virtue of a continuously monitored ventilation system. The building houses two 15,000HP electric drive natural gas compressors. All wiring comes in to equipment from cable tray located below the grating floor and is type TC or MV105, approved for Div 2. My question is are sealoff fittings required where riser conduits from the tray enter the bottom of these NEMA 4 cabinets? Thanks / Phillip

Whenever a cable is to enter a panel you have to install a cable gland and since the panel is located in hazardous area you need explosion proof glands EExd or EExe catagory for the cables.

For the EExd /xe catagory Cable Glands there is no requirement to consider any additional sealant / filler.

Further I guess that unconditional Catagory requirement for your natural gas compressor is Zon1 Div2 and adequate ventilation (for example 15 volume change per hour, NFPA, relaxatins are there)

You are refering to NEMA please refer to NFPA or Institute of petroleum USA publication 500 etc.