Bellows Information

Pressure: The internal design pressure (pressure on the concave side). This value is gauge pressure. When “Solve for Thickness” is selected, this value is an input and should not include static head. When “Solve for Pressure” is selected, this value is a result. In the latter case, it represents the total internal pressure (design pressure plus head) that the component can handle and meet code in the absence of any other loadings.

Temperature: The maximum mean metal design temperature for the internal pressure case as defined in UG-20(a).

Inside Diameter: The inside diameter of bellows convolutions and end tangents.

End Tangent Length: This field is only available for U-Shaped and reinforced U-Shaped Bellows.

Design Life Cycles: The specified number of fatigue cycles.

Fatigue Strength Reduction Factor: This value can range from 1.0 to 4.0 where 1.0 is more favorable for design. For more information, see the fatigue evaluation sections of Appendix 26 for the specified expansion joint configuration.

Ply Thickness: Nominal thickness of one ply.

Number of Plies: This value can range from 1 to 5.

Mean Radius: The mean radius of a U-shaped convolution.

Dis. Attach. Weld to 1st Convolution: The length from the attachment weld to the center of the first convolution for externally attached bellows. This only applies to reinforced U-shaped and toroidal bellows.

Dist. Between Bellows Attach. Welds: The distance between toroidal bellows attachment welds at each end of the bellows.

Max Distance Across Inside Opening: See Figure 26-1-1 sketch (c) for more information. This maximum distance should consider all movements. This input only applies to toroidal bellows.

Bellows Material

Material: A brief description of the component material. When the material selection dialog is used, the default description is based on settings on the Materials-Misc. tab under Tools > Defaults. For example, if the settings are for Spec and Type/Grade and the material is SA-516 Grade 70, this field will show SA-516 Gr. 70. If the settings are instead just for Spec, the field will show SA-516. The field may be edited by the user to say anything without breaking the relationship to the material database; while this flexibility can be very helpful, the user must take care to enter correct information.

Condition: A brief description of the component material. Similar to the "Material" field, the description will default a certain way based on settings on the Materials-Misc. tab under Tools > Defaults when the material selection is used. This field may be edited by the user without breaking the relationship to the material database. As with the “Material” field, the user must take care to enter correct information.

Density: The material density based on table PRD from Section II, Part D. For those materials that did not have a clear match in this table, every effort was made to assign conservative values. Manually editing this field will sever the connection to the material in the database as indicated by the "Unlisted Material" caption.

Hot Modulus of Elasticity: The material modulus of elasticity based on the TM tables from Section II, Part D. The value shown here is based on the applicable TM table and the design temperature listed for the internal pressure condition. In cases where the temperature listed for the internal pressure condition exceeds the highest temperature entry for this material’s TM table, the value will be zero. There are several materials that do not have clear matches in these tables. When a clear match cannot be found by the software’s assignment criteria, the software will instead retrieve the modulus of elasticity from the external pressure chart assigned to the material. If this attempt also fails, then the value will be zero. This is more common with non-ferrous materials. Manually editing this field will sever the connection to the material in the database as indicated by the “Unlisted Material” caption.

Allowable Stress: The material allowable stress at the temperature listed for the internal pressure condition. When a 3.5:1 safety factor is specified in the vessel screen, this value comes from Section II, Part D (Table 1A for Ferrous Materials, Table 1B for Non-Ferrous Materials, and Table 3 for Bolting). If a 4:1 safety factor is specified, this value is calculated based on the ultimate strength from Table U in Section II, Part D; furthermore, the value is limited to the values listed in the allowable stress tables for yield and creep governed cases. In cases where the temperature listed for the internal pressure condition exceeds the highest temperature entry for this material’s stress line, the value will be zero. Manually editing this field will inform the software that the user is defining the material differently than what is stored in the database and the connection to the material in the database will be severed. This is indicated by the “Unlisted Material” caption.

Hot Yield: The material yield strength at the temperature listed for the internal pressure condition. This value comes from Section II, Part D, Table Y-1. In cases where the temperature listed for the internal pressure condition exceeds the highest temperature entry for this material’s yield line, the value will be zero. There are several materials that do not have clear matches in these tables. When a clear match cannot be found by the software’s assignment criteria, the software will calculate the yield strength using the external pressure chart and the method described in UG-28(c)(2) Step 3. This is more common with non-ferrous materials. If no match is found and the software cannot perform the described calculation, this value will be zero. Manually editing this field will inform the software that the user is defining the material differently than what is stored in the database and the connection to the material in the database will be severed. This is indicated by the “Unlisted Material” caption.

Cold Modulus of Elasticity: The material modulus of elasticity at 70 °F (20 °C) based on the TM tables from Section II, Part D.There are several materials that do not have clear matches in these tables. When a clear match cannot be found by the software’s assignment criteria, the software will instead retrieve the modulus of elasticity from the external pressure chart assigned to the material. If this attempt also fails, then the value will be zero. This is more common with non-ferrous materials. Manually editing this field will sever the connection to the material in the database as indicated by the “Unlisted Material” caption.

Poisson: Poisson's ratio for the selected material.

Material Type: There are three options here, Austenitic Stainless Steel, Nickel Alloy, and Other. These affect the calculation of Ysm for U-shaped bellows (both Unreinforced and Reinforced) for code years 2013 and later. This defaults to “Nickel Alloy” and needs to be updated manually despite a material selection.

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