High pressure---low pressure pipe systems

Date 06-17-2009 00:56

Do any of the ASME Codes for Pressure Piping state what is considered to be a low, intermediate and high pressure piping system? I didn't know.
As for boilers, and as far as I know, ASME I doesn't state that either. Now, to keep on talking on boilers, usual custom in Brazil is to consider low pressure up to and including 10 bar (about 150 psig), intermediate pressure up to and including 60 bar (about 900 psig), and high pressure starts at 60,1 bar (about 901 psig). Now, this is the common use in Brazil. I don't know in the USA or Europe.
Giovanni S. Crisi
Sao Paulo - Brazil

By Shane Feder (****)

Date 06-17-2009 01:35

Wolfram,
Have a look at ASME B31.3 Chapter IX High Pressure Piping
Regards,
Shane

By CWI555

Date 06-17-2009 01:38

B31.3:06

300.1.3 Exclusions. This Code excludes the following:
(a) piping systems designed for internal gage pressures
at or above zero but less than 105 kPa (15 psi),
provided the fluid handled is nonflammable, nontoxic,
and not damaging to human tissues as defined in 300.2

There are some caveates in regard to the nature of the fluid, but in general the limit is <15 psi.

The same applies to B31.1 with the exception that it's 15 psig (100 kpa gage) for steam or vapor, and 160 psig (1103 kpa) for high temperature water and/or 250F

Section I:04

PG-2 Service limitations

PG2.1 The rules of this section are applicable to the following services:
(a) boilers in which steam or other vapor is generated at pressures of more than 15 psig
(b) high temperature water boilers intended for operation at pressures exceeding 160 psig and/or temperatures exceeding 250F

Regards,
Gerald

By wolfram (*)

Date 06-17-2009 05:53 Edited 06-17-2009 06:49

Thank you, I was hoping it was going to be a straight forward than that but I knew better. I see in the High Pressure Piping chapter that high pressure is considered herein to be pressure in excess of that allowed by the ASME B16.5 Class 2500 rating. Is that 2500 psi and in reference to this chapter? In that paragraph it also talks about being designated by the owner. What does that mean?
Thanks,
Scott

By jon20013 (*****)

Date 06-17-2009 07:53

Scott, being designated by the owner means exactly what it says. It's possible to fabricate piping of "high pressure" but not classify it as such. It is the Owner's responsibility to make that decision. There's not a lot of differences between the "base B31.3 Code" and Chapter IX "High Pressure" but the committee obviously felt it important enough to separate out. Originally, Chapter IX was developed using ASME VIII Rules but it has not kept up with the times, this is made clear when one tries using nickel alloys or stainless steels for hiogh pressure work only to discover Chapter IX requires impact testing for ALL materials. This has been clarified in ASME VIII and I've submitted a request to B31.3 Committee to change code rules to provide some exemption for these materials (fingers crossed!).

By wolfram (*)

Date 06-17-2009 08:20

jon20013
So in that chapter, what does it consider to be high pressure? Is the 2500 class refer to 2500psi? Thats how I would read it. What would you consider high pressure to be in a process piping system fluid/gas?
Thanks,
Scott

By jon20013 (*****)

Date 06-17-2009 10:50

Scott, see ASME B16.5 PN 420 (Class 2500) rating for the specified design temperature and material group. (This was copied from B31.3). In very general terms, High Pressure is normally considered as 10,000psi or greater although this is difficult to decypher from the code. It's hard for me to comprehend how Ohio considers anything above 15psi as high pressure, this is "almost" atmospheric!

By wolfram (*)

Date 06-17-2009 23:10

jon20013,
The 15psi that I look at is in the Ohio boiler operator licencing. Low pressure licence: < 15psi........High pressure licence: > 15psi.

I called the Ohio state Bureau of Building Code Compliance today and talked to one of the Pressure Pipe inspectors. He always used to consider 100-150psi to be a high pressure process piping system. I say used to because Ohio no longer regulates or inspects piping systems. They are now self regulated in Ohio. Boiler / Pressure vessels are still regulated. Difficult to decypher is correct.

Thank you all so much for the info. A fellow employee asked this question and I wanted to give him a researched answer. 10,000psi, to me is next level high!

Scott

By jon20013 (*****)

Date 06-19-2009 05:42

Scott;

Further on this issue, after careful study of ASME B16.5 its not really that simple.

The greater than 10,000psi answer I gave you was specific to my own project.

If you look at B16.5, it defines ratings by alloy group, pressure and temperature of use.

For "High Pressure" in B31.3, its defined as those pressures that exceed Class 2500 values.

In my case, we are using a 2-1/4 Chrome, 1 Mo alloy and our pressures are somewhere around 14,000 psi. In this instance, at the lowest temperature of use, B16.5 shows Class 2500 rated at about 6,236psi for my specific alloy so clearly we fall into the high pressure category.

Thats the problem of giving "off the cuff" answers! :)

By CWI555

Date 06-17-2009 11:45

That exception should not include cryogenic materials. However, for everything else I agree.