Fluid Pumps

[fifty60]

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..

 

[rbalex]

Unless the application is compliant with Section 501.17 it is difficult for me to understand your description of the installation.

 

[fifty60]

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...

 

[rbalex]

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.

 

[fifty60]

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?

 

[rbalex]

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.

 

[fifty60]

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.

 

[rbalex]

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.

 

[Besoeker]

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

Don't all pumps pump some kind of fluid?

 

[fifty60]

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.

 

[Besoeker]

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.

Excuse my pedantry.................

 

[fifty60]

Pedantry is a curse to the holder, but a blessing to the beholder.

I have another question related to this. So if the inside of the enclosure is Class I Div 2 Zone 2, whereas the hazardous material is only present due to a fault in positive ventilation, where does the Class I Div 2 Zone 2 area extend to.

From NFPA 30, I get the following: "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" (the wording of this doesn't seem to add up to me for some reason)

So is this taking the positive ventilation into account? Isn't it mechanically forcing the air out of the enclosure, so wouldn't that potentially extend the range? I would think that without ventilation, the area would be Class I Div 1, but with ventilation it is Class I Div 2. So isn't the area it is ventilating too become Class I Div 1, or does the ventilate area just extend the Class I Div 2 boundaries based off of the area of classification dictated in NFPA 30?

 

[GoldDigger]

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

Sent from my XT1585 using Tapatalk

 

[GoldDigger]

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!"

 

[fifty60]

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?

 

[GoldDigger]

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.

 

[fifty60]

Ah, that makes sense now. It is still odd to me that a cabinet that without ventilation would be considered Class I Div 1, but with ventilation it is considered Class I Div 2, that there is not any guidlines for the area around the actual ventilation components....It seems like the ventilation considerations would have to carry over into the area that the cabinet is being vented in to...

 

[fifty60]

It seems like the Class I Div 2 area would extend, based off of the installation, to the entire area around the machine in question that could become hazardous due to the malfunction in the machine that would make the machine Class I Div 2.

I think the danger I am trying to avoid is that you could ventilate the enclosure to make it class I Div 2, but the area you are ventilating in to could easily become Class I Div 1 if that area itself is not well ventilated. For example, if I ventilated the enclosure into a sealed off room, eventually the room would become Class I Div 1...but so would the enclosure since the air it is getting from the room to ventilate would be coming from Class I Div 1..

So it seems that calculations need to be done on the machine itself to keep it ventilated properly, but similar calculations need to be done in the room that the equipment is installed in to make sure that it does not become hazardous.

I think that is all elementary reasoning in regards to Hazardous areas...

It seems like the entire machine ventilation method depends on the area of installation being adequately ventilated to begin with. How do you guarantee that the area the machine is installed is always ventilated?

 

[Electric-Light]

well whats the "stuff"?

 

[fifty60]

The stuff in question is flammable refrigerant. The equipment in question has a pump that flows the refrigerant in the liquid state. The reason I am interested in ventilation is to reduce the equipment to Class I Div 2. The reason I think that without ventilation, it could be considered Class I Div 1 is that by the nature of this type of equipment, leaks are pretty inevitable. They are by no means normal, but they are inevitable given time and use.

I always considered Class I Div 1 to be locations where the flammable substance is expected to be present during normal operation. I then always considered Class I Div 2 to be locations where the flammable mixture is only present during a fault of some kind.

Looking more at the definitions, Class I Div 1 can also include situations that flammable mixtures are present due to "frequent" leaks.

I am not sure what "frequent" means, and I am not sure how to determine if leaks in A/C equipment should be considered frequent. I would definitely prefer that the eqipment be Class I Div 2 as opposed to Class I Div 1. For example, Class I Div 1 will allow me to use type Z purge instead of type X or Y.

If the leaks in the equipment can be determined to not be frequent enough to qualify as Div 1, then I also would not have to add forced ventilation to the enclosure to reduce it to Div 2.