How to choose a proper pipe fitting for process application 2

[mechiit]

I am trying to build a process loop with He gas as the working fluid. The max working pressure is 35 bar and temperatures at different locations in the process loop vary from 200 C to 900 C. The pipe material is alloy 800HT (UNS N08811). The line size is 1" (Nominal Pipe Size) and sch. 160. I am planning to use fittings (elbow,Tee etc) of either alloy 800HT or SS316L (as alloy 800HT fittings are really expensive). How should I choose my fitting based on the pressure and temperature (for e.g. fitting is represented as 1" 3000#). How should I decide the correct # rating for a fitting. Where do I get that information from? Pls let me know. Thanks in advance

mechiit

 

[moltenmetal]

Wow- the questions you're asking indicate you're starting from a very basic level of knowledge on this subject to be doing something so hot and high pressure! Sounds like you're doing this for the very first time without the benefit of a course in plant design. Yes the size is modest, but compressed gas at these conditions can definitely kill. You'd better be either hiring out the design to someone competent, or at very least approaching this with extreme caution before you jump into it with some advice from Eng-Tips...

As a very first step, you should read the section on piping design in Perry's Chemical Engineers Handbook. But ultimately you'll need a copy of the applicable piping code because Perry's will only have a limited number of stress value tables for limited materials of construction (not including the 800HT you're using).

 

[ApC2Kp]

mechiit,

The pipe fittings will need to have pressure capability that is equivalent to your Sch 160 pipe. The pressure and temperature requirements would have welded end fittings. The 1" size fittings might be socketweld, except buttweld fittings would be recommended for the temperatures and any thermal cycling service.

The buttweld end fittings for alloy 800HT in size 1" likely are only available as bar stock fittings - bar that has bored out flow passages (match Sch 160) and ends machined for buttweld end bevel preparation. The bar stock fittings would have wall thickness greater than the Sch 160 pipe for equivalent or greater pressure rating.

There are concerns about what you are attempting to do. A little bit of knowledge can be a dangerous thing, but I will add what little that I know about previous high temp helium application to the advice of moltenmetal.

There was a proposed nuclear power plant with graphite moderated core having helium coolant to drive turbines. It was designed and to be built at Fort St. Vrain for Colorado Power. It was cancelled after a fire and loss of containment at a similar design reactor - Chernobyl. Maybe I have my facts wrong, and maybe you are not working on any variation of a helium cooled nuclear reactor.

What are you using 35 bar 900 deg C helium to do?