Question:
When analyzing a model in AutoPIPE Vessel the following warning number was reported.
702 TEST : governing condition, the thickness of one or more components needs to be increased only under the test condition. The MAWP adopted has been reduced to a value lower than the maximum permitted pressure.
Why and how to avoid it?
Answer:
This warning indicates that the hydrostatic test (TEST) condition is more critical than the vessel's normal operating condition.
In this situation:
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- The vessel is acceptable for normal operating pressure.
- However, the specified test pressure produces higher stresses than the operating pressure.
- The current vessel thickness is not sufficient to satisfy the test condition at the calculated MAWP.
As a result, the TEST condition becomes the governing design condition.
Why Does AutoPIPE Vessel Reduce the MAWP?
When the TEST condition governs:
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- AutoPIPE Vessel does not automatically increase the vessel thickness.
- Instead, the program reduces the Maximum Allowable Working Pressure (MAWP).
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This ensures that the hydrotest pressure remains compliant with the applicable design code requirements and that the vessel can safely withstand the specified test condition.
When Does This Commonly Occur?
This warning is frequently seen in:
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- Low-pressure vessels
- Atmospheric or near-atmospheric tanks
- Vessels with very low design pressures
- Models using higher user defined hydrotest pressures
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In these cases, the hydrotest pressure may be significantly higher than the operating pressure, causing the TEST condition to govern the design.
- Accept the reduced MAWP. The reduced MAWP is still greater than the required operating pressure.
- Increase the governing component thickness. It allows a higher MAWP and removes the warning.
- Reduce or modify the test pressure, if permitted by the applicable code, project requirements, or client.
- If user defined Test pressure is defined then remove it and let software calculate it.
See Also