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Thread: Fluid Pumps

  1. #1
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    Fluid Pumps

    I see a fluid pump that is pumping a hazardous refrigerant. It is contained in a mechanical enclosure that is using forced air ventilation to reduce the inside of the enclosure to Class I Div 2. Without the the ventilation, inside the enclosure would be considered Class I Div 1 because leaks in this type of equipment, although not normal, are "frequent" enough to consider rating it Class I Div 1. The ventilation makes it Class 1 Div 2.

    Since the pump is actually in contact with the hazardous material, even though it is in a Class I Div 2 area, would it still need to be explosion proof? I would think that a normal 3 phase pump with no internal thermal protection would suffice. I believe the extra caution is coming from the fact that the pump is actually in contact with the hazardous material....but I don't think the explosion proof motor is absolutely required or even needed since the ventilation takes the entire area down to Class I div 2..
    Time is of the essence, and I am low on essence. ~ Graham Hill

  2. #2
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    Unless the application is compliant with Section 501.17 it is difficult for me to understand your description of the installation.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  3. #3
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    Basically it is a fluid pump inside a cabinet that is ventilated to comply with NFPA 30. Inside of the cabinet, with the ventilation, is considered to be Class I div 2. Would the fluid pump, that is located inside the cabinet, be treated any differently since it is actually pumping the flammable fluid? Or, would it just need to comply with a motor installation in a Class I Div 2 location?

    The cabinet itself is class I Div 2 because it contains mechanical devices that pump and move the hazardous material. So i know that the electrical items inside the enclosure would have to comply to class I div 2. But, the pump located inside the cabinet is actually pumping the fluid, which means that parts of the pump are in physical contact with the flammable fluid.

    I think that the pump would only need to meet the requirements for Class I Div 2, ie no internal thermal protection, etc. But what I see sometimes is that an explosion proof pump is used. I think the explosion proof motor is not necessary since the cabinet is Class I Div 2, even though the parts of the pump are in physical contact with the hazardous material...
    Time is of the essence, and I am low on essence. ~ Graham Hill

  4. #4
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    It sounds like you are dealing with an NFPA 496, Type Y purge. That's pretty complex since the pump is the source. It can be done, but there are a whole bunch of bells to ring, whistles to blow and hoops to jump through to make it comply with Section 500.7(D). See also the definition of Purged and Pressurized and its IN in either Section 500.2 or Article 100, depending on the NEC Edition.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  5. #5
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    I did not think it was possible to do a Purge when the source was inside the enclosure, that is why I was thinking more along the lines of NFPA 30 ventilation. So "frequent" leaks from items like the pump are what make the area class 1 div I, so ventilation takes it down to Class I div II. Does that mean that the pump itself can be Class I Div 2 if the ventilation is set up to satisfy the requirements of NFPA 30?
    Last edited by fifty60; 09-08-17 at 02:13 PM.
    Time is of the essence, and I am low on essence. ~ Graham Hill

  6. #6
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    Read the definition of Purging in NFPA 496:

    Purging. The process of supplying an enclosure with a
    protective gas at a sufficient flow and positive pressure to reduce
    the concentration of any flammable gas or vapor initially
    present to an acceptable level.
    Basically, it's diluting an internal source's concentration. If the source is inside the enclosure - what else are you going to do with "ventilation"? That's the "what-for" for the bells, whistles and hoops mentioned earlier.

    It isn't my favorite protection technique; I avoid it if possible.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  7. #7
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    Understood, and thank you for explaining. My major question is regarding the pump itself. It is a inside the purged or vented enclosure, but the pump itself is in contact with the hazardous material and can be a source of leaks. But it too can now be installed as if in a Class I Div 2 location, just like any other 3 phase motor. A fan motor is more straight forward, because it is not in physical contact with the hazardous material, so I know what kind of motor to use in that situation. But a pump is confusing to me, and not as straight forward.
    Time is of the essence, and I am low on essence. ~ Graham Hill

  8. #8
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    Unless we are dealing with a "canned pump" [Section 501.17 as mentioned before] the pump motor is NOT in direct physical contact with the process fluid and, in that sense, no different than a fan motor. In fact, it is using the process fluid as a coolant.
    Last edited by rbalex; 09-08-17 at 06:32 PM. Reason: A little grammar correction: "since" changed to "sense". (Don't know what I was thinking)
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  9. #9
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    A trivial point in passing - mods be kind....

    Don't all pumps pump some kind of fluid?
    Si hoc legere scis nimium eruditionis habes.

  10. #10
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    The pump motor is not in direct contact with the process fluid, so I agree that at that point it would be like any other motor spec'd for a Class I Div 2 location.

    I can't think of any pumps that pump a solid...so I could have been more specific to say liquid or gas instead of just fluid....since both are fluids, but are subsets of fluids.
    Time is of the essence, and I am low on essence. ~ Graham Hill

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