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Thread: Fluid Pumps

  1. #21
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    You need to study NFPA 497.

    Read carefully, Divisions [Section 500.5] are defined in terms of possibilities not probabilities. "Classic" IEC Zones are defined in terms of probabilities; NEC Zones are somewhere in between to force-fit them (rather poorly IMO) to correspond to Divisions.

    Technically, a Division 1 location may never have an ignitable concentration, it only has to be possible under "normal" operation. An example is the exhaust port of a pressure relief valve that never relieves - it's still Division 1 because if it ever did relieve, it was doing its job. (normal and common aren't synonymous)

    The problem is normal isn't well undefined as it relates to hazardous location operations and Webster's 11th Collegiate Dictionary isn't too helpful either. For an interesting read, see Section 500.8(B)(5) as normal is applied motors.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  2. #22
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    Interesting. Similar to internal thermal protection on a motor....during normal motor operation, there is no hazard. But, for the thermal overload, its normal function is to operate when the motor is under abnormal conditions, so you can't look at the overloads operation as not being normal.

    For A/C equipment, normal operation of the equipment would be to operate the equipment without any leaks present in the equipment. However, leaks are difficult to detect right away, so it is possible to operate the equipment if there is a leaky seal on a valve, for example. Would this still be considered normal operation to the extent to make it Class I Div 1?
    Time is of the essence, and I am low on essence. ~ Graham Hill

  3. #23
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    Actually, if you take it literally, starting a motor isn't normal.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  4. #24
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    I am hoping to be able to find the answers to this in NFPA 497. If I have a nozzle that can dispense a flammable fluid, is the Class I Div 1 (or Div 2) location defined to be wherever the nozzle can reach? Or, is it predefined at the moment of installation to include only the areas the nozzle could reach that contain a source of ignition during normal (or abnormal) operation?
    Time is of the essence, and I am low on essence. ~ Graham Hill

  5. #25
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    Quote Originally Posted by fifty60 View Post
    I am hoping to be able to find the answers to this in NFPA 497. If I have a nozzle that can dispense a flammable fluid, is the Class I Div 1 (or Div 2) location defined to be wherever the nozzle can reach? Or, is it predefined at the moment of installation to include only the areas the nozzle could reach that contain a source of ignition during normal (or abnormal) operation?
    This is a very good question. You have probably discovered by now that the answer is not in NFPA 497 or NFPA 30 either. It's actually in the Article 514 which is mostly extracted from NFPA 30A-xxxx, Code for Motor Fuel Dispensing Facilities and Repair Garages.

    NFPA 30A has quite a history, which you should read in its introductory comments. At one time is was a Subpart of NFPA 30 but has been extracted.

    To get to your specific question, it has nothing to do with the end of the hose. With modern dispensers, it is just basically an application of Section and Table 515.3 and its associated Tables. The theory is that vapor recovery is so stringent with modern dispensers that there is no external Division 1 to the dispenser itself although certain below grade locations will be; e.g., see Figure 514.3.

    Article 514 has had quite a history of its own too. It's worth comparing the aforementioned Figure 514.3 and its predecessors for a few Code cycles.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  6. #26
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    NFPA 70 Article 514 is concerned with Motor Fuel Dispensing Facilities. I will read this, but my concern at the moment is a dispenser for flammable refrigerant.
    Very very interesting. I just made my first read of NFPA 497, and I am comparing this to my study of NFPA 30 this past weekend. It seems to me they contradict each other. NFPA 30 gives rigid definitions of the extent of Hazardous areas, while NFPA 497 gives a lot more leeway and guidance on how to more precisely define a hazardous area.

    I like the NFPA 497 approach better, but what to do if pressed by someone to follow the areas as described in NFPA 30?

    NFPA 497 has a definition for hazardous refrigerant "4.2.4 Compressed Liquefied Gases". But only mentions "Compressed Liquefied Gases" one more time in the entire document. Most of the area diagrams in UL 497 mention "Flammable Liquid". Should I consider "Compressed Liquefied Gases" as a subset of "Flammable Liquids" as far as UL 497 is concerned? I think the answer is yes, but I would like to be more certain that UL 497 is the right standard for flammable refrigerant, or if there is something more relevent.
    Time is of the essence, and I am low on essence. ~ Graham Hill

  7. #27
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    The next step is: is this "hazardous refrigerant" a material listed NFPA 497, Table 4.4.2 or do you have an MSDS for it?

    If the material is a gas in its "natural" state at standard temperature and pressure (STP), you should usually treat leaked product as a gas since it will rapidly become one if it should leak. Its dispersal profile will generally follow its gaseous qualities with some qualification to the size of the aperture, pressure, anticipated flow rate, etc.

    For another analytical approach, you can try API RP 500's Annex D.

    Of course, you can always resort to an NFPA 30 "fugitive emissions" calculation. This usually takes an HVAC expert for proper analysis.

    You will not find a single "formula", "algorithm", or "heuristic" that covers all possibilities. Eventually, you have to make a professional judgement call that you have confidence in. Sometimes it's simple; sometimes it isn't.

    As always, you must understand the process involved and geometry of the installation.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  8. #28
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    One item I see on the MSDS is "Comply with state and local regulations covering liquefied petroleum gases. Comply with NFPA Pamphlet #58." Can you please help me understand what this means? I will get a copy of NFPA Pamphlet #58, but what other regulations covering liqefied petroleum gases should I be concerned with?
    Time is of the essence, and I am low on essence. ~ Graham Hill

  9. #29
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    I suspect it means NFPA 58. (Even an MSDS might not cite and external document correctly)

    So, if we are dealing with LPG (it would have been nice to have known to begin with), see NFPA 58, Section and Table 6.25.2.2.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  10. #30
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    I am actually more interested in HFO refrigerants, and not LPG's at this time. I will get NFPA 58 and study it for LPG applications in the future. Regard NFPA 497, it seems like the dispersion profile is laid out nicely for locations with adequate ventilation. What if the facility is not willing to make any kind of commitments to the ventilation? Can a dispersion profile even be attempted in this case, or does the entire area have to be assumed to be Class I Div 1?
    Time is of the essence, and I am low on essence. ~ Graham Hill

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