Flanges Max Allowable Pressure

[scesare]

My customer has specified some coils for an heat exchanger to be designed at 153.1 barg & 100°C with flanges 900#.
I already bought the flanges and I then realized that for 900# at 100°C the max allowable pressure is well below 153.1 barg, i.e. approx 139 barg!
I checked the worst operating conditions at one of the nozzles, which are 57°C & 147 barg, which are acceptable for 900# flanges.
My question is: can I keep the flanges?

 

[JLSeagull]

You can always keep the flanges. Yes, I am a wise guy - or what.

Forget about ANSI as your information is available in ASME B16.5.

What is the material?

Let's assume some kind of forged carbon steel. So I will select a material table that looks like a potential table for my assumption. Table 2-1.1 is ideal. Yuppers, ya got a problem there cowboy. Other material tables such as type 316 stainless steel only get worse. Class 900 in A 105 and A 216 hits 153.2 bar at 38 degree C. 100 degree C is OK to 139.8 bar.

Howsomever, I would just bet that you could trade those flanges still if on the pallet and material certs in hand. Are you or a materials/purchasing type a pretty good negotiator when it comes to dealing with the seller of the Class 900 steel flange that fails to meet your requirements?

Good luck.

 

[Shmulik]

scesare,
Optional way for using these flanges may be considered whether machining of gasket seat face is allowable / applicable. You may rerate these flanges with a custom gasket seat shape. You may redesign the basic gasket seating width and the location of gasket load reaction. You might be able to find an acceptable design for your working conditions, depending on the following:
1. NPS the flange is intended for.
2. Flange Type: Slip-On, Welding Neck, LWN, etc.
3. Flange ID (in case of Welding Neck type).
4. Flange Material.
5. Nozzle Material.
6. Bolting Material.
7. Gasket Material.
8. Corrosion Allowance.

 

[Ashereng]

900# at 212°F 139 barg seems to be A105 CS?

If your client did the engineering and specified the 900# flanges, I'd suggest you go back to your client and inform them that there seems to be an issue. Maybe they can drop the pressure and/or the temperature requirements?

Otherwise, I would order new flanges. You can always keep the 900# flanges for the next application.

"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?

 

[scesare]

I thank you all for your suggestions and tell you how we solved the issue..
The flange are welded to coils to be submerged in water at atmosperic pressure that could boil. Therefore design temp = 100°C. However, flanges were NOT submerged in water...
Therefore I agreed on with the customer to have a design temperature spec break, with 153.1 barg AND 100°C for coils in water AND 153.1 barg AND 37,8°C for flanges NOT in water.