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  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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    Please don't mix Zones with Classes it adds nothing but confusion.

    Sent from my XT1585 using Tapatalk

  8. #8
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    If the center is Div 2, then the surrounding area cannot become Div 1.
    And normally the area around Div 2 is unclassified, AFAIK.
    The effect of the exhaust in extending that is not clear to me. A lot would depend on where the outflow went. A tall stack would dissipate it nicely.

    Sent from my XT1585 using Tapatalk
    P.S. Churchill is said, when taken to task for ending a sentence with a preposition, to have replied: "That, sir, is errant pedantry, up with which I shall not put!"
    Last edited by GoldDigger; 09-09-17 at 12:15 AM.

  9. #9
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    I am looking at table 7.3.3 in NFPA 30 2015, and it puts forth the "extent of the classified area". The table, imo, is a little bit confusing. It says that for Class I Div 1, the zone extends "Area within 5 ft of any edge of such equipment, extending in all directions". That is straight forward.

    However for Class I Div 2 it says the area extends "Area between 5 ft and 8 ft of any edge of such equipment, extending in all directions; also, space up to 3 ft above floor or grade level within 5 ft to 25 ft horizontally from any edge of such equipment"

    It seems to me like the area of extent for Class I Div 2 is more severe than for a Class I Div 1. I've reread this more than 10 times trying to sort through the ambivalence of the wording, but it still does not make sense. To me, the Class I Div 2 area wording almost says that the zone skips the first 5 feet surounding the edges of the equipment, and does not start until 5-8 feet in totality, and then 5-25 feet 3 feet above the ground. What about the first 5 feet surrounding the edges?
    Time is of the essence, and I am low on essence. ~ Graham Hill

  10. #10
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    Quote Originally Posted by fifty60 View Post
    I am looking at table 7.3.3 in NFPA 30 2015, and it puts forth the "extent of the classified area". The table, imo, is a little bit confusing. It says that for Class I Div 1, the zone extends "Area within 5 ft of any edge of such equipment, extending in all directions". That is straight forward.

    However for Class I Div 2 it says the area extends "Area between 5 ft and 8 ft of any edge of such equipment, extending in all directions; also, space up to 3 ft above floor or grade level within 5 ft to 25 ft horizontally from any edge of such equipment"

    It seems to me like the area of extent for Class I Div 2 is more severe than for a Class I Div 1. I've reread this more than 10 times trying to sort through the ambivalence of the wording, but it still does not make sense. To me, the Class I Div 2 area wording almost says that the zone skips the first 5 feet surounding the edges of the equipment, and does not start until 5-8 feet in totality, and then 5-25 feet 3 feet above the ground. What about the first 5 feet surrounding the edges?
    It seems to me that there is only one type of equipment being considered, and the first five feet around it will be Div 1, while the area from 5 to 25 below 3 feet and 5 to 8 in any other direction will be Div 2.
    You are asking how far Div 2 extends from Div 2 equipment, which does not seem like the right question to ask.

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