Re: CET and MDMT

Samuel,

The simplest explanation is to consider the CET as the lowest metal temperature that the equipment may be subject to while also being at a significant stress (i.e., it is a property of the ambient and operating environments). The MDMT is the lowest temperature that the equipment is actually good for considering brittle fracture using ASME Code rules. The MDMT determined using ASME Code rules for a particular piece of equipment must be no higher than the CET. The MDMT considers the specific material specifications and thicknesses used while the CET is completely independent of those.

API RP 579, "Fitness for Service," has several more detailed definitions of CET. For example, it is the lowest metal temperature at which a component will be subjected to a general primary membrane tensile stress greater than 8000 psi. There are several other definitions that relate it to the vessel MAWP. In setting the CET, you have to look at both the ambient environment and whether particular pieces of equipment could operate at temperatures that are below ambient. Typically there will be a general CET for the equipment site based on the lowest one-day mean atmospheric temperature. Items that operate at temperatures below ambient would have a CET set below that value.

Hope that this helps.

Regards,

Vince

Vincent A. Carucci
Carmagen Engineering, Inc.
4 West Main Street
Rockaway, NJ 07866

Phone: 973-627-4455
FAX: 973-627-3133 Visit our web site at www.carmagen.com
----- Original Message -----
From: "Samuel Liu" <samuel.liu@amec.com> To: <PipingDesign@yahoogroups.com> Sent: Thursday, June 28, 2001 4:13 PM
Subject: [PipingDesign] CET and MDMT

> Does anybody can help me to determine the relationship between CET
(Critical
> Exposure Temperature) and MDMT (Minimum Design Metal Temperature)?
>
> Thanks a lot
>
> Samuel
Received on Fri Jun 29 09:14:00 2001