Pressure Vessel Thickness Calculation for Carbon Steel With Nace

• If the procedure is not to hand, get someone else to do it instead.
• If the procedure is to hand, get a second person to check the design calculations after the procedure has been followed.
• Once it has been second-person-checked, run it by the insurance company's Engineer/Surveyor for review before anything is built.

If it is wrong after it has been built, the insurance inspection will pick it up. It's better to be right beforehand.

Steel strength is steel strength.

Nace as to my knowledge describes a corrosion resistance. So if the specification says 100 ksi it will be 100 ksi. But the material will have to be suitable to your application.

If in doubt www.nace.org

In USA practice, corrosion allowance is added separately after the other stress calcs are done (accounting for temperature, weld efficiency, and material thickness tolerance). The allowable stress value itself does not change.

So, am I right to say that SA516 Gr70 with NACE will have the same Maximum Allowable Stress Value as SA516 Gr70 without NACE?

See #3↑.

Is it possible to use a different wetted material that doesn't corrode? All corrosion affects product quality.

Adding to this one might to allow for additional material if corrosion is not avoidable. But this depends entirely on the application and what corrosion is expected in the system.

...which in turn depends upon the wetting fluid, which the original poster has chosen to conceal from the forum. There is an unfortunate school of thought that everything has to be made from steels, which assumption may be incorrect on occasions.

Mechanical Engineers are bu%%ers for this; basic descriptions of the wetting agent, its temperature and pressure are important nuggets of information. To hell with the corrosion allowance until these things are established!

I have seen a trend in the piping industry. Many customers are ordering heavy gage pipe for corrosion applications. Their view is less intense inspection and a longer life time of the pipe actually cost less over the life time despite the greater cost of making the pipe and delivery.

It is disconcerting that corrosion is allowed and viewed as acceptable by using wetted materials that are incompatible with the wetting fluid. After all, 1973 was a long time ago.

That's until they find that some corrosion does not care about wall thickness and cracks the pipe wide open anyway as in Sour Gas corrosion.

Well we are trying HIC testing to qualify the pipe, but i do not believe that is the total answer.

Calculations will remain as dictated by your code(s) (ASME Section VIII, B31.1, etc.). The material must be ordered as HIC material with material test reports to verify the procedure. The HIC production procedure is to reduce material damage, or destruction, caused by hydrogen induced cracking during normal process operation of the vessel or piping. HIC material is manufactured to the chemical and physical requirements of the code, normalized and to a fine grain practice with vacuum degassing and Calcium/Argon treatment during melting for sulfide control. The material should have a low carbon equivalent (0.37 AVG) for weldability. It will have an extra low 0.002% MAX sulfur content. NDE is normally full (100%) for the pressure vessel and/or piping welds with full PWHT. If you have access to the document, NACE MRO 0175/ISO 15156-1:200(E) is the place to begin. I hope this data gives you some insight to the process.

Thanks for your reply, how about the stress value of the material? Because the stress value will determine the thickness of the pressure vessel.

See #3↑ again.

Someone isn't listening.

Or, if listening is happening, the message isn't taking root.

The stress values will remain as stated in ASME Section II-D, Maximum Stress Values, (per your operating temperature). Your design calculations, per ASME Section VIII, UG-16, UG-27, UG-32, and Mandatory Appendix 1, are applicable.