Nitrogen Stainless Steel Piping 2

[robinxie]

Our client needs a 3" nitrogen transferring piping system with 70,000 scfh flow rate under 100 psig pressure. The client engineer indicated they would like to use stainless steel piping. I just wonder what is the reason behind that? Thanks advance.

 

[Unotec]

They might have lots of money and want their plant to look pretty?

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying ” Damn that was fun!” - Unknown>>

 

[robinxie]

Not this reason. They maybe consider some cryogenic problem when transferring a "big" flow rate of nitrogen. But I do not see any of this kind problem here.

 

[JLSeagull]

Refrigeration is a reasonable guess. If this is associated with air separation; or if there is significant pressure letdown perhaps the system could go below -20 degree F. Another reason for using a stainless steel headers could relate to purity such as an analyzer application.

 

[Unotec]

My reply was not a total sarcasm. The client might require SS for the other applications in the area. There might be a visual issue of why using SS.
I have spent sensible amounts of money on aesthetics in the past.

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying ” Damn that was fun!” - Unknown>>

 

[dcasto]

they don't like paint? Is it liquid N2?

Other than that, there is no reason.

 

[JLSeagull]

The industry matters too. The food and pharmaceutical business uses stainless steel where many industries would use carbon steel.

 

[VikingUK]

What type of pipe material is up/down stream of the new system ? What else is already in the system ? And what are the future add ons (if any) engineer may be thinking of compatibility issues with future or present plant.

 

[SNORGY]

I would wager a guess that the Client is concerned about J-T.

Before going that far, though, maybe suggest this.

Depending on pressure of N2 supply and ambient temperature during purge, consider a precision glass thermometer or skin temperature RTD downstream of the point of N2 injection. You probably don't want too many prolonged excursions down to or near the nil ductility temperature. If brittle fracture is deemed a risk, consider some length of austenitic pipe between the N2 supply and the system to be purged.

Regards,

SNORGY.

 

[BenjaminM]

Perhaps they do not want any possiblity of iron filings or rust being carried though the air lines, though filters at point of use can solve this.

They may have a large stock of S/S pipe on hand.

They may have corrosion issues in the enviroment, and dont want the exterior of the pipe to rust.

Personally I'd wanted to run galvanized pipe for our nitrogen lines, but people started jumping up and down because C/S was $0.50 cheaper foot (there abouts).

 

[Montemayor]

I guess I'm getting very impatient and intolerant of mistakes and illogical engineering thinking in my old age. Therefore, I have to take issue when a ChE states that rust will occur in a nitrogen environment. I could justify a EE (or even an ME) to make that statement. But as a practicing 72-year old ChE, I just can't sit still and allow that statement to go by without being challenged. And I'm not sorry - nor will I appologize. This is basic, practical engineering logic. We are all supposed to use our basic common sense: it takes OXYGEN to produce rust. Nitrogen (being an inert) stubornly refuses to cooperate and do the same. It simply will not contribute to any rust (iron oxide) being produced. This is high school chemistry 101.

The ONLY reason I have used stainless steel in many past applications is because of low temperatures (as has been mentioned) or because it was a food-related application. Otherwise, ordinary carbon steel piping is in order. Purity - such as an analyzer application - has nothing to do with the materials of the piping. An analyzer does not take into consideration the carbon, ferrous, or chromium atoms - at least not to my knowledge.

 

[786392]

I strongly agree to this and have been wandering somewhat why there is so much discussion if

Extremely low temperature service conditions are not the basic issue.and

Even there is no issue of any Oxygen& moisture present.

Best Regards
Qalander(Chem)

 

[SNORGY]

Probably the best thing to do is ask the Client why the Client wants stainless steel piping.

Could be something as simple as the piping isn't always full of nitrogen, so when oxygen *is* or *might be* present, the Client wants to have no risk of corrosion.

Most Clients know what they want and why. Getting their input on operating experience, risks and concerns only makes us better engineers.

Regards,

SNORGY.

 

[BenjaminM]

"Therefore, I have to take issue when a ChE states that rust will occur in a nitrogen environment." -Montemayor

I had a blanket valve fail open. When it was opened up, we found some amount of rust inside the body. We cleaned it out, and reinstalled.

We have a nitrogen generator(separator) on site. It runs around 97-98% purity. There is some small amount of oxygen that is carried over.

We had experienced problems with water in our air lines, I have never found water in the nitrogen lines, but I wouldn't say some amount could not be carried over.

With some amount of oxygen, and some amount of moisture, I would not say rust occuring within a nitrogen line is not outside the realm of possibilities.

We have since resolved the water problems within the air lines.

Now in actuallty, the rust and debris we took out of the valve may have been from fabrication, or could have occured while the piping was out in the yard. The ultimate cause of the failure is the valves were installed without particle filters directly upstream. This has been fixed.

As for my wishes to run our nitrogen lines with galvanized pipe. One of our products is a sodium salt. A by product is regular sodium chloride. Anytime the process piping is opened up or samples are taken, or a sample port is flushed out, if any amount of the slurry is not cleaned up, or is left on the surface of the mezzanines or equipment, when it gets wet from rain, it eats it up. Past better house keeping which is a must, I am looking for an economic alterative to running all piping in stainless to protect it from the enviroment.

 

[strider6]

i tnihk that the reason is that there could be some humidity associated with N2 and this can condense and cause corrosion. the corrosion products can contaminate the gas streams and cause problems to the equipment downstream.
SS is used also for wet air for example for this reason. another possibility is that it's a small piping and thet want to avoid the possibility of external corrosion.
if you look for example in norsok they suggest SS 316 for air and inert gas (pag 17)

http://www.ivt.ntnu.no/ipm/und/fag/k_i/robmat/Forelesningsmatriell/13.10.2004 NORSOK M-001.pdf

S

Corrosion Prevention & Corrosion Control

 

[mydob]

carbon steel becomes brittle under very low temp conditions, if by any chance the temp goes down, the chances of braking that pipe is for sure.
remember it is also under pressure. in the industries ppl always try to save money.
but they give importance to safety as well.
so I think for the same reason they might have used ss

 

[robsalv]

The answer lies somewhere in the advantages of SS over CS. Buggered if I know which advantage is the driver. It could be cold temperature issues, or it could be that they have an external corrosive environment... who knows?? I'd love the OP to ask the client engineer and find out!


As an aside, if I could wave a wand, I would run/replace all our small bore process water, plant air, instrument air, plant nitrogen, steam etc lines in stainless steel. I would in one fell swoop avoid all future external and internal corrosion and painting and the waste of valuable resources involved in even the most simplest replacement work. I think on a life cycle cost basis, the SS would come out ahead.



- - - - - - - - - - - - - - -
"Life! No one get's out of it alive."
"The trick is to grow up without growing old..."