Corrosion resistant piping or protection

[bobinillinois]

Four years ago we put in a painted, galvanized fire sprinkler system in an animal rendering plant. At the time the system was installed we had no idea how wet and corrosive of an environment we were working with.

Now the pipe is falling apart at the fittings and the white nylon coated heads have turned black.

NFPA 13.A.8.16.4.2.1 states, "Types of locations where corrosive conditions can exist include bleacheries, dye houses, metal plating prosesses, animal pens and certain chemical plants.

If corrosive conditions are not of great intensity and humidity is not abnormally high, good results can be obtained by a protective coating of red lead and varnish or by a good grade of commercial acid-resisting paint. The paint manufacturer's instructions should be followed in the preparation of the surface and in the method of application.

Where moisture conditions are severe but corrosive conditions are not of great intensity, copper tube or galvanized pipe, fittings and hangers might be suitable. The exposed threads of steel pipe should be painted.

In instances where the piping is not readily accessable and where the exposure to corrosive fumes is severe. either a protective coating of high quality can be employed or some form of corrosion-resistant material used."

We've talked about using stainless pipe to replace the system but we're not even sure how long the stainless steel would last given the high moisture levels and the corrosive fumes we've got floating around here.

We've tossed around a lot of ideas but none of which I'm comfortable using at this point.

Have any of you dealt with a problem like this and if so, what was your solution?

Thanks.

 

[cdafd]

I take it is a dry system too????

If so is that some of the problem??? As in it is not getting drained??


Wax heads?? To help the head problem

 

[stookeyfpe]

I take it that the appropriate questions were not asked and answered in the developement of the specification.

The H2S generation in a factory where animals are rendered is tremendous. You need to seek professional engineering assistance. Part of the problem could be solved by mechanical ventilation, but such a system needs to consider the biomass decomposition byproducts. To me this is a materials, ventilation and process problem and a internet forum won't bring a solution.

It also sounds like this is a unlimited area building under the International Building Code and it is your client's responsibility to maintain the sprinkler system as that was a condition of the Certificate of Occupancy.

 

[pipesnpumps]

If it is hydrogen sulfide I'd look into using 316SS, although you could likely epoxy coat carbon steel piping and use bagged or wax heads. Unless you have welders experienced with stainless and the tools to do it, that is probably a significant risk. Shielded TIG is a whole different animal. Also a weird thing is, I don't see that stainless steel is allowed by NFPA 13 table 6.3.1.1..

316SS is rated "Excellent" for aqueous and dry hydrogen sulfide. It is resistant to many other acids and bases. Just can't handle any chlorides (salt, bleach fumes, hydrochloric acid fumes, etc.) If you have both chlorides and H2S the only thing you can do is use a proper coating.

Real world knowledge doesn't fall out of the sky on a parachute, but rather is gained in small increments during moments of panic or curiosity.

 

[Sprinklerfitter]

Have you looked into the Viega Pro press solutions? I know they offer both a 304 and 316 stainless line of pipe and fittings, just not sure if the stainless stuff is listed for fire use. Might be worth a call.

 

[DavidCR]

I had a similar problem with H2S vapors in a geothermal power plant. In our case the H2S concentrations comes from small vapor leaks and is low since this is an open area, but moisture and rain help the H2S to do its work in some places.

In our case..., for dry deluge systems, galvanized ASTM-A53 painted pipe do fine but inox is much better.

Teflon coated sprinklers works fine.

Brass accesories are corroded depending on the humidity they are exposed to. For example, around a cooling tower there is a mist that promotes high humidity and only ss works, brass accessories are completely destroyed.

In our case for spray nozzles on dry deluge systems, we prefer to buy brass coated nozzles with lots of spares to change as the get damaged instead buying expensive SS nozzles.

 

[stookeyfpe]

Bob,

You may find some better answers in the Corrosion Engineering forum. I know I've made an assumption regarding H2S that may or may not be correct. Those folks in that forum will probably be more helpful.