Installing an Intrinsically Safe Liquid Sensor in a Class 1, Div 1 Location

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Jon456

Jon456

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Colorado
We have a fleet gasoline dispenser at our facility. There is a containment sump below the dispenser. I need to add a liquid sensor in this sump. The sensor, in conjunction with the alarm system it connects to, is listed as intrinsically safe (UL Class I, Div 1, Group D). The sensor and alarm are made by Morrison Brothers:
Sensor: Model 924LS
Alarm: Model 918Q

My understanding is that this sensor does not require explosion-proof conduit & fittings. I intend to use RMC conduit to bring the alarm wires into the sump, then install a standard (non-hazardous location) threaded aluminum LB condulet. The sensor will thread into, and be suspended in the sump by, the LB. The splices between the sensor wiring and the wires running to the alarm will be made up inside the condulet. Duct seal will be packed around the alarm wires where they enter the condulet from the RMC in order to prevent the passage of vapors.

Does this sound correct?

I don't believe it's required, but I think it would be prudent add a seal-off on the alarm wire RMC where it exits the ground (outside the Class 1, Div 2 zone) and transitions to EMC to the alarm box.

Does this sound reasonable?


Additional questions:

Are there minimum spacing requirements in the ground between this alarm RMC conduit and the RMC conduit that supplies power to the dispenser?

Are there minimum spacing requirements between the alarm EMC conduit and any power EMC conduit that is above-ground (on the outside of a building, beyond the Class 1, Div 2 zone)?

Does there need to be any bonding of the metallic conduit containing the alarm wiring?
 
It is gotten to where every time I answer an intrinsically safe question I begin with, "Do you have a control drawing from the manufacturer as required by Section 504.10(A)?"

Sealing requirements are in Section 504.70. It is a bit more complex than just packing with ductseal.

Separation requirements are in Section 504.30. These rules are quite complex; however, separate RMC raceways should be OK. Check your control drawing.

Grounding and bonding [Sections 504.50 & 504.60] are still a concern.

With all the hoops one must jump through to comply with Article 504, unless it is part of the original design/installation, I have yet to see a cost effective intrinsically safe installation as a retrofit.
 
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rbalex said:
It is gotten to where every time I answer an intrinsically safe question I begin with, "Do you have a control drawing from the manufacturer as required by Section 504.10(A)?"

Sealing requirements are in Section 504.70. It is a bit more complex than just packing with ductseal.

Separation requirements are in Section 504.30. These rules are quite complex; however, separate RMC raceways should be OK. Check your control drawing.

Grounding and bonding [Sections 504.50 & 504.60] are still a concern.

With all the hoops one must jump through to comply with Article 504, unless it is part of the original design/installation, I have yet to see a cost effective intrinsically safe installation as a retrofit.
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Not sure I've ever seen a control drawing from a manufacturer for the install of Intrinsically safe tank monitoring equipment. Possibly I have and didn't know it was called a control drawing. I've certainly never seen a complete site drawing. The 2 companies commonly used around me are Incon and Veeder Root, both have online install instructions and probably a way to become factory certified for installation of there equipment. I'm doubting Morrison Bros has that but maybe? Both Incon and Veeder Root want RMC into the sump and sealoff, such as kilark ENY-2, at first thread into the sump. Junction box on top of the seal off with cord grip on the wire going to sensor.
 
wallyworld said:
Not sure I've ever seen a control drawing from a manufacturer for the install of Intrinsically safe tank monitoring equipment. Possibly I have and didn't know it was called a control drawing. I've certainly never seen a complete site drawing. The 2 companies commonly used around me are Incon and Veeder Root, both have online install instructions and probably a way to become factory certified for installation of there equipment. I'm doubting Morrison Bros has that but maybe? Both Incon and Veeder Root want RMC into the sump and sealoff, such as kilark ENY-2, at first thread into the sump. Junction box on top of the seal off with cord grip on the wire going to sensor.
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If you don't have a control drawing, you aren't complying with Article 504. If you aren't complying with Article 504, you don't have an intrinsically safe system.
 
rbalex said:
If you don't have a control drawing, you aren't complying with Article 504. If you aren't complying with Article 504, you don't have an intrinsically safe system.
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What would a control drawing consist of? I'm assuming it would be site specific?
 
wallyworld said:
What would a control drawing consist of? I'm assuming it would be site specific?
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No. You can recognize it fairly easily in one way: It will be labelled "control drawing" somewhere.

It will show a representation of all of the wiring which must be controlled by the IS specification to make the installation IS. End to end. Including possibly barriers.
It will generally not be site specific.
 
wallyworld said:
What would a control drawing consist of? I'm assuming it would be site specific?
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It's a defined term in Section 500.2. It's also described (in great detail) in ANSI/ISA 12.06.01. It isn't site specific, it is manufacturer/equipment specific. An integrated site document reflecting several control drawings may exist although it should reference the manufacturer's documents.
 
rbalex said:
It's a defined term in Section 500.2. It's also described (in great detail) in ANSI/ISA 12.06.01. It isn't site specific, it is manufacturer/equipment specific. An integrated site document reflecting several control drawings may exist although it should reference the manufacturer's documents.
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Thanks
 
rbalex said:
It is gotten to where every time I answer an intrinsically safe question I begin with, "Do you have a control drawing from the manufacturer as required by Section 504.10(A)?"
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Thank you for your assistance. I don't have a control drawing. I'll contact Morrison Brothers tomorrow and ask if they can provide one. Considering that they are a large petroleum equipment manufacturer, I'm surprised it's not included in any of their PDF downloads, nor is it in their Installation & Maintenance Instructions for any of their tank or sump monitoring devices. Why do they market these devices as intrinsically safe if they don't comply with code requirements?

rbalex said:
With all the hoops one must jump through to comply with Article 504, unless it is part of the original design/installation, I have yet to see a cost effective intrinsically safe installation as a retrofit.
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I don't understand. Doesn't one have to jump through the same hoops for an original design/installation?
 
Jon456 said:
...
I don't understand. Doesn't one have to jump through the same hoops for an original design/installation?
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The hoops are the same but, when IS is part of a large integrated SCADA/DCS system, the economies of scale usually make up the difference.
 
rbalex said:
The hoops are the same but, when IS is part of a large integrated SCADA/DCS system, the economies of scale usually make up the difference.
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I should add small, onesie-twosie IS installations usually have the same problems as retrofits.
 
Jon456 said:
Thank you for your assistance. I don't have a control drawing. I'll contact Morrison Brothers tomorrow and ask if they can provide one. Considering that they are a large petroleum equipment manufacturer, I'm surprised it's not included in any of their PDF downloads, nor is it in their Installation & Maintenance Instructions for any of their tank or sump monitoring devices. Why do they market these devices as intrinsically safe if they don't comply with code requirements?


I don't understand. Doesn't one have to jump through the same hoops for an original design/installation?
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I'd be interested in what you find out from Morrison Bros.
 
Jon456 said:
This was one of the threads I read before when I was planning this sensor install:

http://forums.mikeholt.com/showthread.php?t=76034

Have things changed considerably since 2005? Or did I interpret that thread incorrectly?
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I'm making the possibly wild assumption that you were talking about sealing compounds.

There was a significant addition to Section 504.70 in the 2008 NEC. The phrase, "... but shall be identied for the purpose of minimizing passage of gases, vapors, or dusts under normal operating conditions and shall be accessible" was added to the last sentence. The key word is "identified". While it doesn't necessarily mean listed or labeled it is difficult to clearly establish what is suitable.
 
I haven't had a chance to talk to a Morrison tech rep yet. However, I've been digging into my copy of the NEC (2008 edition) and have come up with a few questions.

Sec 500.2 states:

Control Drawing. A drawing or other document provided​
by the manufacturer of the intrinsically safe or associated apparatus,​
or of the nonincendive field wiring apparatus or associated​
nonincendive field wiring apparatus, that details the allowed​
interconnections between the intrinsically safe and​
associated apparatus or between the nonincendive field wiring​
apparatus or associated nonincendive field wiring apparatus.
​

So that begs the question: what is an "associated apparatus"? From 504.2 we have:

Associated Apparatus. Apparatus in which the circuits are​
not necessarily intrinsically safe themselves but that affect​
the energy in the intrinsically safe circuits and are relied on​
to maintain intrinsic safety.​



To me, this describes an Intrinsically Safe sensor that is connected to a control panel that contains non-intrinsically safe power (e.g., powered by 110VAC). Obviously, there must be some power isolation between the incendive energy in the "associated apparatus" (e.g., the control panel) and the non-incendive energy being supplied to the sensor. Is this a correct interpretation?

But what if the intrinsically safe sensor is not connected to any associated apparatus? What if it's only connected to another intrinsically safe device. In my case, this would be the intrinsically-safe (according to the manufacturer), battery-powered alarm box. Seems to me there is no "associated apparatus" involved. So perhaps there is no need for a control drawing.

But what about 504.10(A)?:

(A) Control Drawing. Intrinsically safe apparatus, associated​
apparatus, and other equipment shall be installed in​
accordance with the control drawing(s).​

It simply states that IS equipment "shall be installed in accordance with the control drawing(s)." To me, that reads: "If there is a manufacturer's control drawing, you must comply with it." But does that mean all IS equipment must have a control drawing, and it's not intrinsically safe without one? I'm not so sure.

And then there's the exception:

Exception: A simple apparatus that does not interconnect​
intrinsically safe circuits.
​

This is not clear to me. Does the liquid sensor, by itself, constitute a "circuit"? I don't see how because, on its own, it has no source of energy. Without being connected to something, it's just an inert object, no different than a piece of metal pipe. To me, the intrinsically safe circuit is the alarm, sensor, and wiring between them. If that interpretation is correct, then isn't the whole alarm/sensor/wiring considered the simple apparatus that falls under the exception?
 
504.10(A) requires the control drawing. If there is no control drawing Article 504 does not apply to the installation and you will have to install per Article 501.
Simple apparatus is defined in 504.2.
 
don_resqcapt19 said:
504.10(A) requires the control drawing. If there is no control drawing Article 504 does not apply to the installation and you will have to install per Article 501.
Simple apparatus is defined in 504.2.
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Thanks for the info. So from reading the manufacturer's description of the 924LS sensor and the 918Q alarm, they appear to fit the NEC definition of a "Simple Apparatus." Also, the NEC definition of a control drawing states that it is "A drawing or other document provided by the manufacturer..."

So does the manufacturer's Installation Instructions count as the "Control Drawing"? It does according to the tech rep at Morrison Brothers. He affirmed that the 924LS sensor, in conjunction with the 918Q alarm does in fact comprise an Intrinsically Safe system when installed per their installation instructions. This is what the instructions state:

WiringNote: As defined in article 501 – Class 1 Locations of the National Electric Code, this apparatus and itsconnected wiring are intrinsically safe. Under normal conditions this apparatus and its wiring cannot releasesufficient energy to ignite a specific ignitable atmospheric mixture by opening, shorting, or grounding.Important: Wiring must be performed by a qualified technician, licensed by the appropriate local, state, andfederal authority. All appropriate precautions and electrical codes should be followed.

Warning: Interconnect wiring between the Sensor and its destination must be kept isolated and separate fromother wiring. This wiring must not share any junction box, conduit, raceway, or fixtures with circuits other thanthose defined by NEC as being intrinsically safe for all Class 1 locations.A. All wires should run in conduits as appropriate per local, state, and federal codes.B. The wires must be #18-22 AWG fuel and oil resistant wire.
​


I had read all this before, which is why I believed the sensor did not require an explosion-proof LB condulet for wire connections, nor a seal-off on the conduit leaving the sump.

So was my original plan sound, or am I still missing something?
 
In my opinion, the equipment is not "simple apparatus" and a written statement is not a control diagram. It would get a red tag from me, unless you can show me an actual control diagram.
 
I'm going to suggest you purchase/download ANSI/ISA 12.06.01-2003 as referenced in Section 504.1 IN. Since it is an ANSI document, it is OSHA enforceable. (CalOSHA too). It has a fairly healthy commentary about what constitutes a control drawing. The Morrison Brothers tech rep's word isn't sufficient. Golddigger's comment in Post #6 is pretty close. The document should self identify itself as a control drawing although it doesn't necessarily have to be a sheet drawing.

There is a lot of other content in ANSI/ISA 12.06.01 you should familiarize yourself with too.
 
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