Material for Instrument Tubing
Material for Instrument Tubing
(OP)
The piping classes are Duplex SS and Super Duplex SS. Can we use SS316 tubing for instruments as DSS/SDSS tubing are not available in market and the next higher grade for tubing available in market is Inconel 625 which is not locally available and will cost heavily.
Service is water injection with high chlorides and also hydrocarbon with H2S and chlorides.
Note: Instrument tubing discussed are only used to drain the fluid when DBB valves are opened. These are connected to the flanges and are used with instruments suchas pressure gauges.
Service is water injection with high chlorides and also hydrocarbon with H2S and chlorides.
Note: Instrument tubing discussed are only used to drain the fluid when DBB valves are opened. These are connected to the flanges and are used with instruments suchas pressure gauges.





RE: Material for Instrument Tubing
You are using SDSS for a reason, the instrument lines should be equal of better.
"C" (276 or 22) tubing is also generally produced.
Yes, it is expensive. But what will failure of these cost you?
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P.E. Metallurgy, Plymouth Tube
RE: Material for Instrument Tubing
RE: Material for Instrument Tubing
While 6% Mo tubing has been used it is all custom made and I don't know of anyone stocking it. That is why I suggested a "C" alloy.
Withing the next 5 years 316 will virtually vanish, with lean duplex alloys taking that slot in the $ vs corrosion resistance spectrum.
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P.E. Metallurgy, Plymouth Tube
RE: Material for Instrument Tubing
RE: Material for Instrument Tubing
It will take time, but I see it starting to happen.
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P.E. Metallurgy, Plymouth Tube
RE: Material for Instrument Tubing
RE: Material for Instrument Tubing
RE: Material for Instrument Tubing
not sure on what you base this.
last time I checked we paid a lot more for DSS compared to standard SS316 fittings (about a factor 10) and tubing (about 7-10 times). as for lean grades, I recently spoke to a guy from one of the bigger stainless suppliers out there who told me their trend is more towards super and hyper duplexes rather than lean ones. the lean ones are typically (only) used for vessel large enough where their price aspect is outweighted by the material weight savings. that aspect is not under consideration in tubing.
RE: Material for Instrument Tubing
RE: Material for Instrument Tubing
I have been involved in a few machining trials and the lean duplex machined as well or better than Prodec and other enhanced machining grades of 3xx.
We have hot worked 2205 and lean duplex, they are no more difficult than 316, just different.
Hot working super duplex is a bear, the temp bands are narrow and the heat treat requirements are very difficult.
I know that Swagelok charges a premium, but we have made production runs of welded and drawn tubing in LDSS that was the same price as 304L.
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P.E. Metallurgy, Plymouth Tube
RE: Material for Instrument Tubing
RE: Material for Instrument Tubing
The tubing isn't the hang up, the valves and fittings are.
My hunch is that the next time we have an economic expansion you will see some of the guys doing it.
We are ready to make runs as soon as someone will place an order. We have done some isolated jobs with lean duplex, but I don't see people expanding inventory these days.
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P.E. Metallurgy, Plymouth Tube