Gas pipe exposed to fire

[Brandon Whitmore]

Are any of you aware of any testing standards regarding natural gas piping that has been exposed to fire. I ran into an unusual sitation the other day, and want to CYA.. Thanks.

[Les]

I have no standard. I would be concerned about the fittings, IE: thread compound/lubricant and effects on dis-similiar materials when heated.

[Eric B]

I'd defer to the "highest authority" - the local gas company.

[mlparham]

Are any of you aware of any testing standards regarding natural gas piping that has been exposed to fire. I ran into an unusual sitation the other day, and want to CYA.. Thanks.

When in doubt, throw it out.

[Brandon Whitmore]

I'd defer to the "highest authority" - the local gas company.

Ummmm.... that's me.

When we're told there has been a house fire, we pull the meter. As soon as we are told the customer wants service restored, we install a meter and activate service. We don't have any standards regarding exposures to fire, etc.

I tell contractors they need to do a pressure test, but I guarantee most don't do it.

On Thursday, I showed up at a house where we were told there was a house fire. The entire basement was black. The "fire restoration" contractor was there, and I told him we were pulling the meter. He was upset and told me he needed heat and hot water by Sunday. How someone could be living in those conditions, I don't know. The upper level must have smelled something awful.

The original cajun style water heater was sitting next to a brand new 80% furnace that was in operation. They at least sealed the return air registers and ran a return air duct to the exterior of the house. I told them they should have all pipes inspected/ pressure tested, but of course we were called to restore gas service the following day.

[Jim Katen]

I thought that you guys were omnipotent. Why can't you just tell them that they have to perform a pressure test and show you the pressurized gauge?

[Brandon Whitmore]

I thought that you guys were omnipotent. Why can't you just tell them that they have to perform a pressure test and show you the pressurized gauge?

As far as I can ascertain, we have zero standards regarding testing/inspection standards regarding housepipe exposed to heat/ fire. That's why I was trying to find something externally that I could take to the higher ups.

I'd like to see that change.

[Les]

Brandon,

go to SAE for the fittings and thread compound specs. I know there has to be a standard for temp limits, just too lazy to look.

[Brandon Whitmore]

Thanks Les,

I checked a few manufacturers NPT thread sealant products, and it looks like the max. temp. rating varies, but is in the 300-500deg. range.

[Kyle Kubs]

Hey Brandon,

If the pipe was heated to a significant extent and then hit with water in the process of putting out the fire, it has likely had it's temper significantly changed/hardened, which would make it more brittle, especially at the threaded joints. I would imagine that somewhere deep in ASHRAE standards there is some range of hardness that the pipe is supposed to conform to. I would try contacting a pipe manufacturers association.

[resqman]

Wood self combusts at 451 degrees. If there was a fire, it was hotter than 451. Your sealant is toast, litteraly.

[Brandon Whitmore]

Wood self combusts at 451 degrees. If there was a fire, it was hotter than 451. Your sealant is toast, litteraly.

My fairly useless degree is in structural fire science.....

Kyle,

Thanks for bringing this post back up. I needed the reminder to look into this more.

[Jim Katen]

Wood self combusts at 451 degrees. If there was a fire, it was hotter than 451. Your sealant is toast, litteraly.

Why would that be a problem? The sealant mostly serves as a lubricant. If the fire is over and the pipes hold pressure, why would it matter if the sealant is toast?

[Jim Katen]

Hey Brandon,

If the pipe was heated to a significant extent and then hit with water in the process of putting out the fire, it has likely had it's temper significantly changed/hardened, which would make it more brittle, especially at the threaded joints. I would imagine that somewhere deep in ASHRAE standards there is some range of hardness that the pipe is supposed to conform to. I would try contacting a pipe manufacturers association.

I'm not going to say that it isn't possible, but that scenario is really unlikely. Have you ever tried to temper a piece of gas pipe?

[Brandon Whitmore]

The sealant mostly serves as a lubricant.

That's true in theory; NPT is supposed to seal up without thread sealant. There's at least one pipe dope (blue crap) that tends to prevent a proper pipe to pipe seal.

[Hearthman]

You would have to local a reputable testing lab or engineering firm that conducted a "failure mode analysis" on the product. Meanwhile, understand the code rubber stamps the std. to which the product has been tested. If the std. for steel pipe does not contain any sort of fire endurance test, then it must be assumed to suffer degradation and not meet the std. In other words, that's not the same pipe that rolled off the line, therefore replace it. Since fire is so random I don't see any way of knowing whether one end of the same pipe was annealed while the other end was hardened and everything in between suffered intergranular corrosion. Stainless steel chimney liners get this with the formation of chromium carbides at high temps. resulting in stainless steel that rusts. It has changed. Some for your steel pipe. It did its job--it survived the fire and now should be replaced.

[mlparham]

Hey Brandon,

If the pipe was heated to a significant extent and then hit with water in the process of putting out the fire, it has likely had it's temper significantly changed/hardened, which would make it more brittle, especially at the threaded joints. I would imagine that somewhere deep in ASHRAE standards there is some range of hardness that the pipe is supposed to conform to. I would try contacting a pipe manufacturers association.

Not likely. That pipe is a cold rolled product with no heat treatment or tempering. I stand by my option that if you are dealing with gas piping "When in doubt, throw it out".

[Jim Katen]

You would have to local a reputable testing lab or engineering firm that conducted a "failure mode analysis" on the product. Meanwhile, understand the code rubber stamps the std. to which the product has been tested. If the std. for steel pipe does not contain any sort of fire endurance test, then it must be assumed to suffer degradation and not meet the std. In other words, that's not the same pipe that rolled off the line, therefore replace it. Since fire is so random I don't see any way of knowing whether one end of the same pipe was annealed while the other end was hardened and everything in between suffered intergranular corrosion. Stainless steel chimney liners get this with the formation of chromium carbides at high temps. resulting in stainless steel that rusts. It has changed. Some for your steel pipe. It did its job--it survived the fire and now should be replaced.

On the other hand, we're talking about a piping system that has to contain contain a gas at a whopping pressure of 1/4 psi. That's less pressure than it takes to blow bubbles in a glass of milk with a straw.

[Hearthman]

A piping system where the ends are weakened by cutting threads into them then people hang stuff off the poorly supported pipes as if they are clotheslines.

[Jim Katen]

A piping system where the ends are weakened by cutting threads into them then people hang stuff off the poorly supported pipes as if they are clotheslines.

Or do chin-ups from them. I hear you. I just think that the chance of real damage to the pipe is awfully remote.