Chlorine Atmosphere

gadfly56

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
I have a customer that processes grey water for use in process cooling. This involves treatment with chlorine, among other things. The exhaust fans they had in the treatment building have corroded to unusable. They ventilate the building by opening a man door on each side off the building 24/7/365. Into this mix we have a fire alarm panel that went into a Hoffman box, but since they were ventilating it with the corrosive atmosphere, the components didn't last long. We are relocating the new panel to an enclosure at ground level in a breezeway under the building. Although not a part of the current work, eventually we need to replace the devices. We are going to go with conventional devices hooked up to monitor modules in the environmental cabinet. The EMT for the fire alarm devices in the building is completely wrecked and should be replaced. Does anyone have a recommendation that doesn't involve plastic coated RMC?
 
Chlorine + humidity = hydrochloric acid.
They do make stainless steel EMT and fittings but it will be pricey.

In reworking some controls for potable water storage where they added chlorine to the water, I saw that any of the electrical parts that made a little bit of heat were fine, but parts that stayed at room temperature were damaged fairly quickly. We ended up moving the control panels outside like you are doing, but there were still things inside like pressure sensors and push buttons were an issue.
 
For an idea of what we're dealing with, here's an example.

20250515_131521vsmall.jpg
 

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don_resqcapt19 said:
Unless you can make that vapor tight, that will be an ongoing problem.
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Yes, we are going to have to have a conversation with the customer about how we can make this work going forward, The monitor modules will be OK. We can relocate them into the new environmental enclosure. The real trouble is the relay modules. They are supposed to be within 3 feet of the controlled device which means being in the chlorine atmosphere. I'll have to put my thinking cap on for this.
 
gadfly56 said:
Yes, we are going to have to have a conversation with the customer about how we can make this work going forward, The monitor modules will be OK. We can relocate them into the new environmental enclosure. The real trouble is the relay modules. They are supposed to be within 3 feet of the controlled device which means being in the chlorine atmosphere. I'll have to put my thinking cap on for this.
Click to expand...
It seemed that a small amount of heat eliminated the problem in the control panels I worked on....maybe a small heat pad?
 
gadfly56 said:
Yes, we are going to have to have a conversation with the customer about how we can make this work going forward, The monitor modules will be OK. We can relocate them into the new environmental enclosure. The real trouble is the relay modules. They are supposed to be within 3 feet of the controlled device which means being in the chlorine atmosphere. I'll have to put my thinking cap on for this.
Click to expand...
Purged and Pressurized?
 
Few things survive chlorine intact. Where duct work, fans are exposed it has to be coated.
One manufacturing co. had a coating for their heat exchanger in a rooftop hvac system.
I would guess they lost some efficiency.
Most metals will react.
A house was with an inside swim pool wanted to take advantage of the humidity the pool provided
and use it in the rest of the house.
They had the chrome eaten off all the faucets within one year.
 
don_resqcapt19 said:
It seemed that a small amount of heat eliminated the problem in the control panels I worked on....maybe a small heat pad?
Click to expand...
If everything were in one location, it might be an option. I doubt we can sell the labor it would take to make this work, especially without some kind of guarantee.
 
xformer said:
Purged and Pressurized?
Click to expand...
Coming from an explosives background, this was an option I was thinking of. It remains to be seen if there is a source of clean dry air nearby. Some of my colleagues had a chuckle when I floated this, but we'll see.
 
Sometimes a picture is worth 1000...... but if the owners haven't visited the site bring them pictures.
Some people think their way and some want to see the problem.
 
xformer said:
Purged and Pressurized?
Click to expand...
We had a problem at a Dairy manure treatment building where the fumes would eat the copper braided wires inside of the CBs. We had them pressurize the room with the freshest air they could find. The dairy went through at least three manager changes after it was installed and before I retired. Betting dollars to doughnuts that system is rusted to oblivion after no maintenance and no one knowing why it's there.
 
So now that we completed the actual paid scope, which was replacement and relocation of the panel, the customer wants us to replace the non-functioning devices. They are well aware that this is likely a very temporary solution, but it's their money. New panel shot below.


Panel Shot1mb.jpg
 
Peracetic acid (PAA) versus chlorine, do a web search for indepth discussion / information.
Paracetic acid can meet the most treatment goals just as chlorine does.

Use CPVC for piping if possible , good for about 20 years of working use.

Other possible solution, conformal spray coating spray can delivery such as:

Humiseal 1A33 aerosol conformal coating technical data sheet


Consult Manufacturer for your application recommendation
 
Sheet metal can be bought that is coated to resist chlorine.. Last time I used it I told it was PVC coated
but it could be something else. Pricey.
The other halogens like fluorine also can be a problem.

Chlorine is so reactive that many things are effected even concrete. Plastic seems to survive.
 
DooWop said:
Sheet metal can be bought that is coated to resist chlorine.. Last time I used it I told it was PVC coated
but it could be something else. Pricey.
The other halogens like fluorine also can be a problem.

Chlorine is so reactive that many things are effected even concrete. Plastic seems to survive.
Click to expand...
The new enclosure is well out of the corrosive atmosphere. It's sheltered under the building in a tunnel-like structure open at both ends. Only thing to worry about is ambient temperature.
 
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