Thick Wall Expansion Joint - MDMT Other

Owned by Former user (Deleted)
Last updated: Oct 12, 2016 by Mike Clark
2 min read

Perform MDMT Calculations

Perform UCS-66 calculations: Selecting this check box will cause the software to perform UCS-66 toughness calculations on the component. This option is only available to materials that are classified as UCS materials per Table UCS-23.

Exemption Drop-down: When UCS-66 calculations will not be performed (the software will not allow these calculations when a non-UCS material is used), an exemption must be entered. The exemption may be typed in or selected from the drop-down options, but the user is responsible for ensuring that the exemption selected is valid for the material, service, etc., in question.

MDMT

Apply UCS-68(c): Selecting this check box will give an additional flat reduction in the allowed MDMT per UCS-68(c). Carefully review this paragraph as there are steep requirements for this exemption.

MDMT Curve: The notes in Figure UCS-66 provide the criteria to assign the MDMT curve to the material and product form of the component. Curve A will give the least favorable allowed MDMT and Curve D will give the most favorable allowed MDMT. When UCS materials do not have a clear match using the criteria, they are assigned a conservative value of A. As the software cannot currently obtain possible improvements in curve rating due to heat treatment and other factors, the user may override the curve value.

MDMT Pressure: The net internal pressure (concave side) on the component coincident with the minimum design metal temperature (MDMT). This includes static head.

Requirements

Per UG-23(e), calculate using: Select whether to calculate the allowable primary plus secondary stress using 3xS or 2xSy. Caution: If 3xS is selected and the value of S is determined at 90% of Sy, the allowable primary plus secondary stress will be 2.7xSy.

Use High alloy steel minimum thickness requirements: Select this box to use the minimum thickness requirements for high alloy steel (0.125", 3mm).

Fatigue

Design Cycles: Specify the number of design cycles for operation.

Fatigue Reduction Factor: The fatigue strength reduction factor is affected by many variables, including sharp corners, surface roughness, etc. Expansion joints that include these items should reflect this with a higher value. Higher values will lower the allowable fatigue strength of the design.