Difference between "CLASS" and "LBS" in "Valves" 11

I need someone to clarify my doubts in the field of "Valves".

How the flange rating of the valve must be mentioned with "CLASS" or "LBS"
Example: CL 150 or 150 LBS

Thanks.

 

[Hush]

Class. Class 150 describes the geometry only. Pressure rating will depend on material and temperature.

 

[TD2K]

Flanges used to be described as 150lb, 300lb, 400lb, 600lb and so on and you'll still hear that terminology.

The more accepted terminology today is class as in class 300 flanges because as Hush said, the actual allowable pressure rating is a function of the temperature and material the flange is constructed of.

However, the pressure rating of either a 'class' 150 set of flanges or a 150 'lb' flange would, for the same material, be exactly the same and is set per ANSI B16.5.

 

[hammerr]

For flanged valves, you may want to check out ANSI B16.34 for pressure/temperature ratings.

 

[valvetech]

TD2K and Hammer have cover this with the best possible answer, when in doubt about a rating check with the ANSI listing and you can usually find it.

 

[manian]

i understand LBS is an older terminology and the correct
method to designate would be to use CLASS according to ASME B16.34

Regards

Manian

 

Pounds (lbs) when referring to flange or valve ratings is slang. The proper terminology, particularly when specifying either, is Class. The ASME Classifications, 150, 300, 400, 600, etc.) provides categories of pressure/temperature limitations based on material of construction. Both Code and manufacturer's specifications will specify or refer to Class. It's acceptable to use pounds when referring to flanges or valves in a discussion, but not in written specifications.

Good luck,

WMH

 

[VenPipingEng]

It is important being "formal" when referring to flanges/valves "classes" otherwise you will have problems like the one I am about to tell you:

When purchasing valves we (as a Company) requested Class-1500 Gate Valves and the vendor supplied 1500-Lbs Gate Valves ... guess what happened when we hydrotested those lines .... this "1500-Lbs" designation is related to Maximum Allowable Pressure of the Valve which is totally different from Class-1500 meaning ... be aware of that ...as WMH said: "is SLANG"

 

[owlscreech]

Until the publication of B16.5-1973, valve pressure ratings were determined by B16.5, "Steel Pipe Flanges and Flanged Fittings". When "classes" of fittings were originally established, the pressure class of the valve was the allowable pressure [in psig] at 850F [except the 150 class that used 500F] and carbon steel was assumed. Using the material properties for carbon steel at 850F, the minimum wall was established. Using the minimum wall, the process was reversed for other materials to give allowable pressures. If you go to the 1968 edition of B16.5, you will find the last use of "lb" to describe the pressure ratings, as well as the last time you will find the 850F "rule."

In 1973 B16.34 was first issued to cover butt-welding end valves. Concurrently B16.5 was also issued and covered just flanged valves. [The title of 16.5-1973 explicitly has the word "flanged valve." Earlier editions considered valves as "fittings." Butt-welding end valve were covered although not explicitly.] Both B16.5 and B16.34 presented a revised rating basis and both contained a completely revised set of rating tables. The use of "lb" was completely eliminated. Wall thickness was established using the class designation in psi, i.e., for Class 150, Pc = 150 psi, and a stress factor of 7000 psi. The pressure temperature tables were then generated based on material properties and temperature. In 1977 flanged valves were moved from B16.5 to B16.34.

So the proper term is Class 150, Class 300, etc. "Lb" is not proper, but is used frequently, usually as "300 lb Class," etc, by the old-timers and thus it is perpetuated.

 

looking to spec a valave for installation in a natrual gas skid thta supports a Combustion Turbine. The operating perameters are:

8' shced 80 piping SA-106
operating pressure is 700 psi
design pressure is 1440 psi
less that 100deg F.

3' shced 80 piping SA-106
operating pressure is 700 psi
design pressure is 1440 psi
less that 100deg F.

These valves will be used to isolate NOT Throttle.

 

[vpl]

Benton

Not really sure what your question is - but suggest posting it as a new one. Patricia Lougheed

 

[01101998]

owlscreech
Can you please eloborate "for Class 150, Pc = 150 psi, and a stress factor of 7000 psi."

Thanks