Check ASME Vessel and Exchanger Stresses Before Testing
The ASME Code requires that all vessels undergo hydro (or pneumatic) testing following fabrication and before Code stamping. As this test provides mechanical stress relief it may be thought of as the final step in the fabrication process. The hydrotest is an effective way to screen for design, material and fabrication deficiencies as well as to prove the structural integrity of the equipment.
However, this raises the question - what constitutes a hydrotest "design deficiency"? Although ASME Section VIII-1 does not prescribe a test stress limit, vessels that undergo "objectionable distortion" during testing may be rejected by your AI. The COMPRESS Hydrotest Feature assists you by:
How do I view the Hydrotest Report?
The Hydrotest Report is available to all COMPRESS users. To prepare your report:
Criteria for Limiting Hydrotest Stress in COMPRESS
Because ASME VIII-1 does not provide guidelines for determining allowable stress values for the test condition, COMPRESS uses the following method by default. It is taken from the 2004 Edition of ASME VIII-2, paragraph AD-151.1. If needed, you can define a different percentage of yield allowed at test in the Set Mode Options > Defaults > Testing area.
(a) Pm ≤ 0.9 * Sy
(b) Pm + Pb ≤ 1.35 * Sy for Pm ≤ 2 / 3 * Sy
(c) Pm + Pb ≤ 2.2 * Sy − 1.5 * Pm for 2 / 3 * Sy < Pm ≤ 0.8 * Sy
In the equations above, Pm is the primary membrane stress and Pb is the primary bending stress. The yield stress Sy is taken as the smallest of the shell, reinforcing pad or nozzle neck Sy values.
The discontinuity stress state at a nozzle includes both primary membrane and bending components. As equation (a) governs for shells and either equation (b) or (c) governs for nozzles, the test allowable may be different for nozzles and shells even when they are made from the same material.
Find Out More
How to Specify a Corroded Vessel Hydrotest in COMPRESS
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