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Joined: Jan 2005
Posts: 5,316
Cat Servant
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Well, winter is here, and I have a cold-related issue to solve.

We have a spray booth, essentially outdoors. The sprayer arrangement uses pumps to spray paint on product as it passes through on a conveyor.

Outside of the immediate spray area are the supply lines - and the cold is making them freeze up. This area does accumulate overspray.

Any thoughts -pro or con- to using electrical heat tape to keep the lines and valves - all outside the tube in which the spraying takes place- from freezing? Would the type of heat tape matter?

2017 / 2014 NEC & Related Books and Study Guides
Joined: Apr 2002
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Reno:
A quick reply is 'yes' heat trace will be OK. As to what type, depends on the o/s temp range, type of pipe, type of overwrap insulation, etc. Definately a 'regulated' heat trace. Look in WWGrainger catalog, or google.


John
Joined: Jan 2004
Posts: 1,507
G
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Reno- I would suggest getting someone with the authority to classify the area do so and then design and wire accordingly. Article 516 addresses the spay area and openings within 3' of the spray area but you indicated that the heat tapes could be subject to overspray. I don't know if they make Listed heat tapes for a classified area. The main thing I would ask for, as an inspector, is that someone has classified the area so the engineer or electrician has a place to start their work.


George Little
Joined: Jul 2004
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Is the liquid paint flammable? Are the atomized paint / fumes flammable? Can the paint supply lines be insulated? What do they use for cleaning out the paint sprayers? Is it flammable? Is it reactive to certain materials?

Joined: Jul 2002
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John,
I'd tend to think that merely lagging the pipes would probably solve this problem.
I'm leaning towards the foam insulation that is used with Air Con/refrigeration piping.

Having said that, once you start getting into heat traces and what-not, you start needing things like intrinsically-safe supplies and explosion-proof connection boxes, even if it isn't inside the actual "hazardous area".
I'd try the lagging first.

Joined: Apr 2002
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Reno:
As I quickly said earlier...yes, it can be heat traced. Other members jumped in and asked most of the ?? I did not have time to get into this AM.

Basically, the ball is back in your court.

The 'overspray' situation could be mitigated (particles) by something as simple as boxing-in the pipes. As to the classification of the area surrounding the pipes, that's a lot of 'ifs'. Barriers, openings, etc., or is the paint a latex or other 'safe' formulation?

If you follow this link.... http://www.chromalox.com/productcat...=44&gclid=CKvx4-Pc9KUCFaVx5Qod4nXGow

You will find classified/hazardous location heat trace equipment, but watch your wallet!!


John
Joined: Jul 2004
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G
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Thinking outside the box, so to speak, could they loop warm water through pex pipe, sistered to the paint lines and under the armaflex. The heater could then be outside the classified area


Greg Fretwell
Joined: Jul 2002
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Actually Greg, that is a damned good concept, one that could even be taken into the spray-booth itself, as it uses no electricity.
Maybe you could send one of your water-cooled computers Reno's way! grin
Just kidding.

Joined: Jan 2005
Posts: 5,316
Cat Servant
Member
John, thanks for the link; I'll keep that in mind.

The operation is, for all practical purposes, outdoors. Sure, there's some structure around and over the area, but there are so many major -and necessary- openings that fresh air is abundant.

The 'paint' used has an extremely volatile and very flammable solvent. The paint itself - even in dried form- burns like rocket fuel. "Overspray" perhaps isn't the right term - perhaps it's better to say that enough particles get airborne, drift about, and settle on every surface that keeping the sprinkler heads functional is a challenge.

We did have the place catch fire once, and it was over in moments - a flash fire that consumed all long before any response could be mounted.

The material is pumped direct from its' shipping container to the spray jets, using flexible hoses, for a distance of perhaps six feet. These, and the air-powered valves at the spray assembly (technically outside the spray area) are what have been freezing up.

Really makes me wonder what they've been doing for the past twenty years when it got cold. I'm afraid to ask.

It is claimed that we are converting to a less flammable material, and that an entirely new booth will be installed next summer.

In the meanwhile, I've already made the point: we really need to have an engineering study performed, to define the classification of the areas.


Last edited by renosteinke; 12/18/10 01:17 PM.
Joined: Jul 2004
Posts: 783
L
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Quote
These, and the air-powered valves at the spray assembly (technically outside the spray area) are what have been freezing up.


How dry is the compressed air?

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