Stainless to copper transition for fire stopping
Stainless to copper transition for fire stopping
(OP)
Hi All,
I’ve noticed a copper spool fitted to otherwise stainless-steel pipework. The length of the spool was approx. 10 pipe diameters and the installer’s explanation was that the spool is installed to stop the fire spreading inside the pipe.
Is this a good practice or a legislative requirement? Could a flame arrester be used instead of a copper spool?
The materials are connected via a brass flange on the copper side which probably acts as a dielectric union. The fluid in question is the Oxygen.
Regards
I’ve noticed a copper spool fitted to otherwise stainless-steel pipework. The length of the spool was approx. 10 pipe diameters and the installer’s explanation was that the spool is installed to stop the fire spreading inside the pipe.
Is this a good practice or a legislative requirement? Could a flame arrester be used instead of a copper spool?
The materials are connected via a brass flange on the copper side which probably acts as a dielectric union. The fluid in question is the Oxygen.
Regards
RE: Stainless to copper transition for fire stopping
You must understand that oxygen systems are quite unique and the gas makes those systems subject to possible internal fires . No other commonly used industrial gas poses this hazard !!!
The United States of America has done much research in past decades regarding safe handling of both gaseous and liquid oxygen. This takes the form of NASA SAFETY STANDARDS .... used for decades throughout the world. Potential internal ignition mechanisms and ignition sources have been researched.
http://brcompliance.com/wp-content/uploads/NASA-Ox...
Copper and some copper alloys are suitable for use in oxygen systems at all pressures. Copper can be particularly useful for resisting ignition by particle impact ... but only when the whole system is made of copper
What I believe that you question regards is something called a "Fire stop" ... It is an old practice ...
It is discussed in this document:
http://asiaiga.org/uploaded_docs/AIGA%20021_12%20O...
Fire stops are short spool pieces of copper or nickel-based alloy. Their use is no longer considered common practice in steel pipeline transmission or distribution systems.
Smaller devices (called "flashback arrestors") exist for industrial gas systems. They are mandatory for oxygen and acetelene service. These are designed and certified specifically for smaller HP oxygen systems.
https://www.linkedin.com/pulse/flashback-oxygen-ac...
I do not understand the mechanism by which a short section of copper pipe can protect against internal fires in an entire oxygen system
Best Regards
MJCronin
Sr. Process Engineer
RE: Stainless to copper transition for fire stopping
RE: Stainless to copper transition for fire stopping
RE: Stainless to copper transition for fire stopping
The arrestors that we installed were basically spool pieces (SS just like all of the piping) filled with a coarse Cu wool.
People used to install Cu or Monel spool pieces plain steel piping in order to stop burning of the steel itself.
Given enough oxygen and ignition source everything will burn.
That is what makes oxygen so scarry to work with.
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P.E. Metallurgy, consulting work welcomed
RE: Stainless to copper transition for fire stopping
The ignition source can be as simple as shavings in the pipe, and the velocity being high enough that the grit hitting the inside of an elbow creates a momentary hot spot,
If you are building or maintaining oxygen piping systems these documents explain the hazards well.
ASTM G128 Standard Guide for Control of Hazards and Risks in Oxygen Enriched Systems
ASTM G88 Standard Guide for Designing Systems for Oxygen Service
Oxygen Safety: Swagelok provides some of the scary information discussed in the astm documents. Document is attached.
RE: Stainless to copper transition for fire stopping
G-4 (and all of the sub-documents) are oxygen related.
G-4.4 id specifically piping systems.
https://portal.cganet.com/Publication/index.aspx
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P.E. Metallurgy, consulting work welcomed
RE: Stainless to copper transition for fire stopping
As to the purpose of the copper spool and the mechanism how it works, I believe the idea for the spool is to melt down and stop the fire that way. I have only seen the flame arresters doing the same.
Regards