Piping Versus Pressure Vessels

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Frequently it is difficult to decide if a unit being incorporated into a piping system should be classed as piping or as a pressure vessel. No precise differentiation exists; hence the classification must be left to engineering judgment. The unit should be called piping, however, if: 1. As a part of the piping system, its […]

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Internal Loads

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Pressure vessels normally contain various internal components that are attached directly to a vessel’s shell, such as distributor trays, catalyst support grids, baffles, and demister pads, etc. These internal components apply loads to the shell, and thereby develop stresses that must be added to those resulting from the internal pressure. The weight of the internal […]

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Lifting Lugs

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Lifting lugs must be provided for moving and erecting a pressure vessel. The location of these lugs and the loads that will be applied to them depend on how the vessel will be moved and erected. The details are usually worked out between the fabricator of the vessel and the construction contractor who will be […]

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Attached Equipment

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Other equipment, such as reboilers or valves, occasionally are connected directly to pressure vessel nozzles without providing separate support. The weight of this equipment results in forces and moments on the nozzles that develop local stresses in the vessel’s shell similar to the stresses caused by piping connections. If these stresses are great enough to […]

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Structural Attachments

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Platforms and ladders are frequently supported by direct attachment to a pressure vessel. The normal practice is to provide a sufficient number of clips welded to the vessel’s shell such that the local load transmitted to the shell by any individual clip is not great enough to affect the design of the vessel. This may […]

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Piping Connections

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Stresses can be developed in a pressure vessel shell due to forces and moments that result from piping connections to nozzles. The magnitude of these forces and moments applied to a vessel are relatively insignificant and need not be considered for the design of a vessel. This is especially true for vessels designed according to […]

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External Loads

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External loads applied to a pressure vessel are usually of a local nature. WRC Bulletin 107 provides the almost universally accepted methodology for calculating the stresses that these loads develop in the shell of a vessel, and for determining the effect that they will have upon the design (i.e., the minimum required thicknesses for the […]

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Corrosion Allowance

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The internal process environment that a pressure vessel is exposed to during operation can frequently cause the material to corrode. Therefore, a corrosion allowance must be added to the calculated minimum thicknesses required for each component of the vessel. The Code assigns to the owner/user of the vessel the responsibility for specifying the corrosion allowance. […]

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Wind and Earthquake Design

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The potential wind and earthquake loadings on a pressure vessel are specific to the geographic location where the vessel is installed. Design parameters for the United States can be obtained from maps published by API. Refer also, to the Civil and Structural Manual. Section 440 of this manual describes how these design parameters are used […]

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Minimum Temperature

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A minimum permissible temperature is required to be displayed on the nameplate of a Division 2 vessel. Unlike the nameplate for a Division 1 vessel, a coincident pressure is not displayed for the minimum permissible temperature. However, the pressure during startup or shutdown is explicitly not permitted to exceed 25% of the design pressure (defined […]

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