Class1 Div2 Battery Box

[BZ2005]

Working on the engineering side of a quote in a C1D2 area, the customer want's a battery box that feeds backup power to the control panel. (12vdc controller memory). The battery box they detailed is an open vented box with two 100Ah 12vdc batteries in it. The control panel will have a purge on it and conduits will all be sealed on boths ends, standard C1 D2 installation sort of stuff. But this battery box. Does anyone have experience with this sort of situation? (Seems to not meet code.) I have to look into NEC exceptions, and possible requirements for local disconnect options but...
Any advice ?

 

[rbalex]

I admit this one has me scratching my head. Based on a few basic principles, I don?t see that the battery or the enclosure specifically requires being identified for Class I, Division 2, but I can't point to any specifically applicable Code Section at the moment either. Let's see how far we can reasonably go before we throw our hands up. One thing is for sure though, Class and Division aren't the only area classification issues to consider; we will also need to know the Group and especially the location?s T-rating.

Off the top of my head some other things we will want to consider: How will the batteries be charged? If a HAZLOC installation were not a consideration, would the installation otherwise be consistent with Article 480? Flame arrestors and/or pressure relief devices [480.10 (A) & (B)] could be the kiss of death.

I will probably think of a few more things as we go through the exercise - and if you DO find someone who has successfully approached this situation, I would sincerely like to know what they did.

 

[JWCELECTRIC]

BZ,

Do they want the batteries with vented enclosure in the C1D2 area? I agree it dosen't seem logical to put them it in the classified area. Art 504 Intrinsically Safe Systems comes to mind. I think this battery circuit (12v DC) is in violation since it is above the 1.5v threshhold?

- JWC

 

[tkirk]

I know that SLA batteries are routinely installed in vented enclosures in C1D2 groups C & D locations on oil and natural gas wells. The enclosure has to be I think NEMA 3R or better (don't quote me on that, writing from memory), but should be vented to allow any gases produced by the battery when charged to escape without building up.

Batteries over 25AH do fall under a bit different requirements, and might not be allowed to be charged without current limiting circuitry attached directly to the battery to effectively make it IS (see 60079-11). If you look at 60079-15, clause 15, protection method "n" is applicable to most batteries, and there is a list of requirements for the enclosure, essentially to ensure that the enclosure will not corrode or short out the battery.

Usually there is a required warning label stating that you are not allowed to connect or disconnect any of the battery power terminals unless the area is known to be non-hazardous, since that could generate a spark.

It might be a requirement to have a field listing done of the battery system as a power supply rated for C1D2 using protection method "n" if the inspector requires a listing label on the battery enclosure.

Obviously, any equipment installed in the battery box including charge controller would need to be rated for C1D2.

TK

 

[weressl]

BZ,

Do they want the batteries with vented enclosure in the C1D2 area? I agree it dosen't seem logical to put them it in the classified area. Art 504 Intrinsically Safe Systems comes to mind. I think this battery circuit (12v DC) is in violation since it is above the 1.5v threshhold?

- JWC

Division 2 would not require intrinsically safe circuits, unless there are switching components associated withe the circuit and there are no other options available for the 'switches' to be deployed.

 

[weressl]

I admit this one has me scratching my head. Based on a few basic principles, I don?t see that the battery or the enclosure specifically requires being identified for Class I, Division 2, but I can't point to any specifically applicable Code Section at the moment either. Let's see how far we can reasonably go before we throw our hands up. One thing is for sure though, Class and Division aren't the only area classification issues to consider; we will also need to know the Group and especially the location?s T-rating.

Off the top of my head some other things we will want to consider: How will the batteries be charged? If a HAZLOC installation were not a consideration, would the installation otherwise be consistent with Article 480? Flame arrestors and/or pressure relief devices [480.10 (A) & (B)] could be the kiss of death.

I will probably think of a few more things as we go through the exercise - and if you DO find someone who has successfully approached this situation, I would sincerely like to know what they did.

The simple approach would be to examine that under normal operation:

• does it contain arcing devices
• does it produce heat at temperatures exceeding 80% percent of the AIT?

Flame arrestors prevent ignitable mixtures reaching outside of the battery 'jar' itself, so the prevent external ignition. Pressure relief vents are relieving the internal pressure under abnormal charging or discharging conditions. Both of these conditions are abnormal operations and thus need not be taken into consideration in Division 2 areas. The enclosure should be vented, but it has nothing to do with the classification requirements.

This is my take on it anyway.

 

[BZ2005]

All
Thanks for the input.
The classified area is C1D2 Group B, (Hydrogen service) And yes the 3R box is specifically vented into the Classified Area,
I can only image the batteries Seal Lead Acid, or something very similar although I do not see any charging circuit for the batteries within there diagrams. Only a temp probe (going to assume they are changed off site/ safe location.) Or charger is C1D2 rated.
I know it would be required to to have a "nameplate" on the enclosure, for potentially explosive atmosphere when servicing.

I would say that this would be ok to do because the batteries are passive (no acing) and they should never be able to reach the ignition temp when properly controlled.

For now I simply noted in my quote that this design is on the customer, since they would be supplying the battery pieces to me.
If this quote does come through, i will have to fully re-live this issue

 

[rbalex]

All
Thanks for the input.
The classified area is C1D2 Group B, (Hydrogen service) And yes the 3R box is specifically vented into the Classified Area,
I can only image the batteries Seal Lead Acid, or something very similar although I do not see any charging circuit for the batteries within there diagrams. Only a temp probe (going to assume they are changed off site/ safe location.) Or charger is C1D2 rated.
I know it would be required to to have a "nameplate" on the enclosure, for potentially explosive atmosphere when servicing.

I would say that this would be ok to do because the batteries are passive (no acing) and they should never be able to reach the ignition temp when properly controlled.

For now I simply noted in my quote that this design is on the customer, since they would be supplying the battery pieces to me.
If this quote does come through, i will have to fully re-live this issue

Hydrogen (Group B, T1) can be both very nasty and rather benign, depending on the circumstances. In sufficient quantities it produces extremely violent explosions and has one of the widest flammability ranges (4 to 75%) and lowest minimum ignition energies (MIE). On the plus side it really does take a lot to be violent and, since it is much lighter than air, it dissipates fairly quickly and has a high autoignition temperature (520C) so electrical equipment only requires a T1 rating.

One of the ?fire jobs? I was involved with repairing occurred when a hydrogen cloud was released from a compressor system and was ignited by a flare stack over 500? away. When it happened, the windows of my home (~40 miles away) rattled. Fortunately, there were no fatalities or serious injuries and, since the fire plume was mostly high in the air and was consumed fairly quickly, very little direct fire damage occurred. However, it literally crushed several cooling towers and a major substation. This put the facility out of general production for several months.

Laszlo and TK either directly addressed or touched upon my basic concerns.

Assuming charging is properly dealt with; the only thing I would worry about is the disconnecting means. In general, Section 480.5 would imply a disconnecting means is not absolutely required for the 12V batteries. That would concern me in a classified location since they would still need to be replaced periodically and I would want to assure myself that there would be no possible arcing when they were removed/re-installed ? even in a Division 2 application. Otherwise, I?d say go for it.

 

[weressl]

Hydrogen (Group B, T1) can be both very nasty and rather benign, depending on the circumstances. In sufficient quantities it produces extremely violent explosions and has one of the widest flammability ranges (4 to 75%) and lowest minimum ignition energies (MIE). On the plus side it really does take a lot to be violent and, since it is much lighter than air, it dissipates fairly quickly and has a high autoignition temperature (520C) so electrical equipment only requires a T1 rating.

One of the “fire jobs” I was involved with repairing occurred when a hydrogen cloud was released from a compressor system and was ignited by a flare stack over 500’ away. When it happened, the windows of my home (~40 miles away) rattled. Fortunately, there were no fatalities or serious injuries and, since the fire plume was mostly high in the air and was consumed fairly quickly, very little direct fire damage occurred. However, it literally crushed several cooling towers and a major substation. This put the facility out of general production for several months.

Laszlo and TK either directly addressed or touched upon my basic concerns.

Assuming charging is properly dealt with; the only thing I would worry about is the disconnecting means. In general, Section 480.5 would imply a disconnecting means is not absolutely required for the 12V batteries. That would concern me in a classified location since they would still need to be replaced periodically and I would want to assure myself that there would be no possible arcing when they were removed/re-installed – even in a Division 2 application. Otherwise, I’d say go for it.

Thanks for the wisdom and the tale Bob!

Disconnecting can always be restricted to be performed with a special 'hot work' permit with the use of an an LEL meter present to assure when the connection is broken no flammables exist in the area. That is a pretty routine way of handling these type issues.

 

[rbalex]

Thanks for the wisdom and the tale Bob!

Disconnecting can always be restricted to be performed with a special 'hot work' permit with the use of an an LEL meter present to assure when the connection is broken no flammables exist in the area. That is a pretty routine way of handling these type issues.

I wouldn't have a problem with this approach as long as it's a written policy for the facility and there are proper warning signs to observe it.