Which American standard mentions that Lb can be used as a unit to represent pressure?

American standard valves have their nominal pressure indicated in pounds; this value is the result of calculations based on the melting temperature and pressure of a certain metal, and it is determined in accordance with ANSI B16.34 standards. The pound rating and the nominal pressure are not in a one-to-one correspondence, mainly because they have different temperature references. We usually use software for calculations, but we also need to know how to use tables to check weight classes. Regarding the pressure of gases, in China we generally use its mass unit, “kilogram”, to describe it (rather than “jin”), with the unit being kg. The corresponding unit of pressure is “kg/cm2”; one kilogram of pressure means one kilogram of force applied to one square centimeter. Similarly, as is the case abroad, the common unit used to measure gas pressure is “psi”, which stands for “1 pound/inch2”, that is, “pounds per square inch”. The full English name for this unit is Pounds per square inch. But it is more common to refer directly to its unit of mass, namely pounds (LB); in fact, LB refers to the pound-force mentioned earlier. By converting all units to metric units, the following conversions can be made: 1 psi = 1 pound/inch2 ≈ 0.068 bar; 1 bar ≈ 14.5 psi ≈ 0.1 MPa. Countries in Europe and the United States typically use psi as their unit of measurement. For Class600 and Class1500, there are two different values corresponding to the European and American standards: 11 MPa (corresponding to the 600-pound class) is the value specified by the European system, as outlined in the standard \"ISO 7005-1-1992 Steel Flanges\" ； 10 MPa (corresponding to the 600-pound class) is specified in the American system, as outlined in ASME B16.5. Therefore, it cannot be said absolutely that a 600-pound class corresponds to 11 MPa or 10 MPa; the regulations vary depending on the system.

It was included in the old flange standards, but it doesn’t seem to be clearly stated – Class 150 means 150 LB, that’s all that’s indicated.

It seems that what the original poster is asking about is, in the flange standards, for Class 150, where it is specified that instead of writing \"Class\", one can write \"LB\".

Well, it’s more or less that meaning. Just like the US standard models have “Lb” after them, what is the standard that determines the use of LB?

This post was last edited by chenbin_XLYQ on 2018-12-19 at 14:58

This post was last edited by Baoji ChaoSheng Titanium Industry on 2018-12-19 at 15:17. The original poster shouldn’t worry – flanges meeting American standards also have pressure ratings indicated in psi!

Well, it seems you’ve found the source, so the problem is solved. :victory:

It’s also possible to run into strict owners or third parties who say, \"Show me the evidence – which standard states that Class can be changed to LB?\"

I guess the old standard was like this; I checked the standards from 2003, 2009, and 2013, and in none of them was the term LB mentioned.

I guess the old standard was like this; I checked the standards from 2003, 2009, and 2013, and in none of them was the term LB mentioned.