MIKMET
Member
- Location
- Kennebunkport, Maine
We have a project in progress that utilizes a large number of miniature pneumatic solenoids in a potentially hazardous area, if there were a leak of a flammable gas.
The enclosure/area has not been formally identified as a Class I Div. 2 area per NFPA 497 or otherwise.
The area is within a high purity piping system in a well ventilated enclosure, provided with "adequate protections against failure" (exhaust failure interlocks to turn off gas sources and turn off all power to the devices within the box). It is also provided with gas detection. The solenoids are pilots for SS diaphragm valves.
We are in the process of having the nearly completed systems evaluated to SEMI S6, a semiconductor equipment standard, by a third party contractor.
The standard primarily defines minimum exhaust rates based upon tracer gas testing to ensure a worst case toxic gas leak is captured, and also addresses flammable leaks.
It requires that leaks are considered as if the line were completely severed and the full capacity of the gas line leaks into the enclosure. It then requires that the tracer gas testing ensure that the leak does not create a concentration greater than 25% of the LEL at any source of ignition. Exhaust is increased and established as a baseline to the level to ensure this.
Since the potential leak points for the tracer gas injection during the test will be in close proximity to the solenoids, and the Engineer considers the solenoids to be potential sources of ignition, the exhaust rate required will be extreme, likely beyond the capacity of the ducting of the system and the end user facility.
The Engineer at the evaluating contractor has suggested that we have a Class I Div 2 area in the case of this worst case leak, and that we should use the definition of source of ignition from the NEC.
I suggested that solenoids are not ignition sources per the code, but he does not agree.
The solenoids are linked here: http://content2.smcetech.com/pdf/S070.pdf
These are not listed or marked for Class I Div 2, but I do not think that they need to be per code and other references, including several in this forum.
I sent the note below to make my argument:
Class I Div 2 allows devices that do not spark, such as those identified in 2011 NEC, Article 501, Section III, Equipment.
Of these, of interest to us, the solenoids:
"501.105 Meters Instruments and Relays
(B) Class I Division 2
(3) Without Make or Break Contacts. Transformers, windings, impedence coils, solenoids, and other windings that do not incorporate sliding or make-or-break contacts shall be provided with enclosures. General Purpose Enclosures shall be permitted."
Also:
Regarding interpretation of that section of the NEC from NFPA experts:
From Electrical Installations in Hazardous Locations, by Peter Schram and Mark Earley, published by the NFPA:
"In a Class 1 Division 2 location....solenoids without arcing or sliding contacts may be installed in general purpose enclosures; their lack of contacts makes them incapable of igniting a hazardous atmosphere"
from: https://books.google.com/books?id=o4...cts%22&f=false
None of this has so far convinced the Engineer, but he has promised to keep an open mind and look at whatever we send.
I'm curious if anyone here any further documentation or publicly available information or references regarding the use of "ordinary location" solenoids in Class 1 Div 2 area.
Comments are also welcome!
Thanks,
Mike
The enclosure/area has not been formally identified as a Class I Div. 2 area per NFPA 497 or otherwise.
The area is within a high purity piping system in a well ventilated enclosure, provided with "adequate protections against failure" (exhaust failure interlocks to turn off gas sources and turn off all power to the devices within the box). It is also provided with gas detection. The solenoids are pilots for SS diaphragm valves.
We are in the process of having the nearly completed systems evaluated to SEMI S6, a semiconductor equipment standard, by a third party contractor.
The standard primarily defines minimum exhaust rates based upon tracer gas testing to ensure a worst case toxic gas leak is captured, and also addresses flammable leaks.
It requires that leaks are considered as if the line were completely severed and the full capacity of the gas line leaks into the enclosure. It then requires that the tracer gas testing ensure that the leak does not create a concentration greater than 25% of the LEL at any source of ignition. Exhaust is increased and established as a baseline to the level to ensure this.
Since the potential leak points for the tracer gas injection during the test will be in close proximity to the solenoids, and the Engineer considers the solenoids to be potential sources of ignition, the exhaust rate required will be extreme, likely beyond the capacity of the ducting of the system and the end user facility.
The Engineer at the evaluating contractor has suggested that we have a Class I Div 2 area in the case of this worst case leak, and that we should use the definition of source of ignition from the NEC.
I suggested that solenoids are not ignition sources per the code, but he does not agree.
The solenoids are linked here: http://content2.smcetech.com/pdf/S070.pdf
These are not listed or marked for Class I Div 2, but I do not think that they need to be per code and other references, including several in this forum.
I sent the note below to make my argument:
Class I Div 2 allows devices that do not spark, such as those identified in 2011 NEC, Article 501, Section III, Equipment.
Of these, of interest to us, the solenoids:
"501.105 Meters Instruments and Relays
(B) Class I Division 2
(3) Without Make or Break Contacts. Transformers, windings, impedence coils, solenoids, and other windings that do not incorporate sliding or make-or-break contacts shall be provided with enclosures. General Purpose Enclosures shall be permitted."
Also:
Regarding interpretation of that section of the NEC from NFPA experts:
From Electrical Installations in Hazardous Locations, by Peter Schram and Mark Earley, published by the NFPA:
"In a Class 1 Division 2 location....solenoids without arcing or sliding contacts may be installed in general purpose enclosures; their lack of contacts makes them incapable of igniting a hazardous atmosphere"
from: https://books.google.com/books?id=o4...cts%22&f=false
None of this has so far convinced the Engineer, but he has promised to keep an open mind and look at whatever we send.
I'm curious if anyone here any further documentation or publicly available information or references regarding the use of "ordinary location" solenoids in Class 1 Div 2 area.
Comments are also welcome!
Thanks,
Mike
