Condensation in explosion proof enclosure

[mikeh6]

I have an explosion proof electrical product that is getting a lot of mositure in it that I believe is condensation and I'm trying to prevent or reduce the condensation.
The product is installed outdoors in a very warm to hot rainy and humid environment. It is a NEMA 4 & 9 / IP66 rated enclosure. The electrical connection is through an explosion proof cable gland screwed into a 1/2" npt opening.
I believe warm moist air enters the device through the cable entrance and/or through the flame path of the device as it "breaths" throughout the day and night. There are no water marks on the flame path but there is calcuim deposits under the cable where it enters the product.

We cannot put a vent or drain into the device because of the Listings and Approvals of the device.

Would it help if the electrical connection was in conduit and a breather was installed in the conduit?

Any help is appreciated.

thanks,
mike

 

[itsmoked]

It is a common problem because of the weight (mass) of the EXP enclosures that causes them to thermally lag behind the environment's temp swings, resulting in the inside being below dew point frequently. It is in thru the flame path and your cable entry is not the problem unless you have some nefarious water situation where water is being delivered down the cable.

There are two solutions. One is to heat the enclosure. It doesn't take much at all, it just needs to be a few degrees above ambient to have all condensation stop. The other is to purge the enclosure, which works in some cases where a purge gas source is already present but is considerably more expensive if not.

For heating there are heater bars for just this purpose available.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jraef]

You realize hopefully that there ARE explosion proof rated breathers and drains made for exactly this reason, right? So if you were aware of those, what is the objection to them? If you were not, here's what they are:

http://www.cooperindustries.com/con.../catalog-pdfs/fittings/ecd-breather-drain.pdf

"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[waross]

As Keith said, it doesn't take much heat. Typically the heaters are energized at 50% of rated voltage and energized 24/7. At 50% voltage the power consumption is low and the life is greatly extended. Heater failure alarms are also common.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[mikeh6]

I'm not sure a heater is an option. This product is an explosion proof pressure switch that is monitoring a fire sprinkler system. It is installed outdoors. I'm not sure what type of power would be available for a heater. Space inside the pressure switch is very limited.

I am aware of explosion proof vents and drains. My question about them was would they help if they were on the electrical conduit and not actually on the pessure switch? The electrical opening of this device is near the top, just below the removable cover.

There is only one conduit entrance to the device.

Why do you think the moisture is entering through the flame path instead of cable entry, because there is so much more of it? just curious.
I have seen pictures of the device and the flame path is clean and dry. The cable inside the device has water droplets on it and calcium deposits below it.

thanks,
mike

 

[jraef]

It's doubtful that moisture is entering through the threads. It's more likely that the air in the unit and the conduit feeding it provides enough moisture to condense. Is the conduit not sealed? This is a common issue with low energy instrumentation that uses intrinsically safe circuits. No need to seal the conduits so they don't, but that allows for enough air volume to create noticeable condensation. Can you seal the conduit or at least put a fitting in the conduit with a Y trap and a drain?


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[mikeh6]

I'm not sure if they have conduit or not. I'm trying to find out. This installation is in Singapore. In some areas over there they just run cables to the device and the cable connects to the device through an explosion proof cable gland.

So I was wondering if a vent in the cable would work, then I could tell them to install the device using conduit and an explosion proof vent on the conduit as close to the pressure switch as possible.

 

[waross]

You have mentioned calcium twice.
Condensation does not contain calcium.
I suspect that the switch may be leaking and allowing fire protection water into the enclosure.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ScottyUK]

Calcium deposits, or aluminium corrosion byproducts?

 

[Kiribanda]

mikeh6,
If your enclosure is flame proof and specified corectly it should have come with a "COMBINATION BREATHER & DRAIN" so that it can breath
due to temp variations and then you can drain the condensed moisture from bottom time to time. Also you have to seal properly
all conduits entering the enlosure to stop as much as possible the moisture coming to the enclosure. I believe it will reduce the moisture
condensation inside. If the enclosure is certified flame proof, then now you are not permitted to install a breather and a drain
to it due to insurance issues etc. Therefore, the best action I can see is to order a proper FP enclosure with a
breather and a drain and seal the conduits as much as possible coming to the new enclosure.

 

[mikeh6]

The device is not leaking sprinkler water. The deposits must not be calcium, it is probably aluminum corrosion from the condensation.
I don't know if I can post a link on this site but I'll try. Here is a link to the product.

http://www.pottersignal.com/product/datasheet/5400982_PS10EX.pdf

As I mentioned, I do not know if conduit is being used. It may just be exposed cable connected through an explosion proof cable gland.

If I can get them to use conduit, would a vent in th econduit located near the pressure switch help?

thanks,
mike

 

[BJC]

Calcium? Could it be magnesium from MI cable?
Both of the following have the best write up on explosion proof systems.

http://www.cooperindustries.com/con...fs/other-pdfs/crouse-hinds-codedigest2014.pdf

http://www.emersonindustrial.com/en..._flyers_pdf/nec-code-review-2014-appleton.pdf

 

[mikeh6]

Please see the attachment. Do you think this would help allieviate the condensaton problem?
Even if they still use cable instead of conduit?
We can't put the vent or drain directly onto the product because of Listing and space issues so this would close nipple it to the product.

thanks,
mike

 

[mikeh6]

Sorry, not sure that last attachment was explosion proof.

mike

 

[motorspert]

Hi Mike
The enclosure is aluminium and I assume the gland is brass? The moisture is causing galvanic corrosion between the two materials and aluminium being the anode is corroding. There is a galvanic voltage of 0.5V between the two materials. An aluminium gland would solve this problem if such a thing exists in a flameproof form. A plastic gland would be even better, they do exist with the relevant certification and would be the cheapest solution. Alternatively a plastic adapter between the gland and the housing would work as well. The condensation will still exist, but wont be caise any corrosion so you will be able to live with it.

 

[mikeh6]

I'm not sure the gland is brass, it's hard to tell in the attached picture. Also, I can't live with the condensation, that is the problem. There is so much condensation inside the device that it is making the Microswitches fail. See the attached pictures.