Re: Why Class 150 ?

From: <Christopher>
Date: Fri May 07 2004 - 17:06:00 EDT

>Here's hoping someone can clear up a long-standing and nagging question.
The name just evolved over time like pipe sizes and gauge numbers. The pressure designations for flanges are temperature dependent that using the ANSI ratig scheme which is close but not exactly the same as the Boiler code rules for flanges. I have an ancient Tube Turns catalog showing pressure temperature ratings for flanges and it turns out that the pressure rating of a class 150 flange is 150 psi at 500F. At room temperature the rated pressure is 275F. For other classes the nominal ratings usually obtain for 800F. That's for carbon steel. For other steels and gasket combinations different ratings obtain.

The term Class 150 is someone's idea of nicer terminology. The term used to be ASA 150 lb class, meaning 150 lb/in^2 for the rated pressure and temperature. The ASA becames ANSI and the designation became ANSI 150 lb. Probably to remove the implied units designation in a metric world the designation changed to ANSI class 150.

I should probably note that there are other flange types floating around whoch are classed at room temperature, so the wide margin between the class designation and the allowable pressure at room temperature doen't always hold.

Christopher Wright P.E. |"They couldn't hit an elephant at <a href="/group/PipingDesign/post?postID=CIGnn0lKaWcQCIUYZqngf1B49FcqizjpcTR1jdYVlfJDpglAwA0-fpcQpQ_LmGRjq0RUQL-jYygo-w">chrisw@skypoint.com</a> | this distance" (last words of Gen.

___________________________| John Sedgwick, Spotsylvania 1864)

<a href="http://www.skypoint.com/~chrisw">http://www.skypoint.com/~chrisw</a> Received on Fri May 07 17:06:00 2004