Hastelloy C-276

[centaur21]

I am new to the instrumentation side of EE and need some expertise on a particular subject. I am checking some PIT spec sheets and have run across the term Hastelloy C-276. I have read that it has a much better resistance to corrosive material, as opposed to SS. I see that they use the Hastolloy material for the body when seawater is the process, which makes sense. But I was also informed that it is used when sour gas is the process and under a high temp, otherwise would use SS (sour gas and temp is low).

So my question is, what is the cutoff line temperature b/t using the SS body or the Hastelloy body? Thanks!!

 

[JLSeagull]

For instruments such as pressure transmitters, factors other than the body material limit the temperature. The properties of Hastelloy C-276 appear to be suitable toward 900 degree F. The diaphragm fill fluid is not.

 

[unclesyd]

Hastelloy C-276 has some very severe limitations when used in liquid corrosive media. Each process application should be considered based on the characteristics of the process media. While C-276 is very good in most liquid reducing environments it is generally unsuitable for most liquid oxidizing environments.

 

[centaur21]

I have cleared up a few things. The elements diaphragm is Hastelloy, but the body is either SS or Hastelloy. I see that they are using Hastelloy when seawater is the process, which could be a corrosive liquid. But would SS be just as good, or are there many other factors to consider before making such an assumption? I am seeing inconsistencies here and trying to clear them up.

 

[JLSeagull]

Check the projec piping specifications. Some companies regard type 316 stainless steel to be acceptable for seawater. Other companies do not. Some companies prefer nickel alloys such as Monel for seawater. If you purchase alloys greater than 316 stainless steel some companies require positive material identification and material certification. Those with lots of surplus money may require gold-plated diaphragms.

 

[Ashereng]

You need to talk to a material/metalurgist regarding material suitability.

Sea water is not sea water. Different seas have different water. You need to take a water and analyse it, and then match the metal to the water.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[centaur21]

Thanks for the info guys. I appreciate that. Thanks again!

 

[jmw]

For information on Hastelloy, see:

http://www.haynesintl.com/Walloy/H3017Ap4.htm

JMW

http://www.ViscoAnalyser.com

 

[JimCasey]

I have been told that one reason for Hastelloy diaphragms in transmitters is that Hastelloy has better fatigue resistance than 300-series stainless.

 

[JLSeagull]

About five years ago my favorite transmitter peddler had to recall a batch of transmitters with Hastelloy diaphragms and did not recall their stainless models.