I have a problem with the hydrotest pressure when designing heat exchangers. The shell side I think it runs OK, but not for the channel side.


The hydrotest type is UG-99(B) note 33. In the formula appears:

UG-99(b) Note 33, Test Pressure Calculation [Channel Side]:
= Test Factor * Design Pressure * Stress Ratio
= 1.3 * 3.000 * 1.000
= 3.900 bars

The stress ratio is always 1.000, independently of the design temperature. Could it be possible? I think it is wrong or I am doing something incorrectly.

Many thanks.

Hello Jose,

The stress ratio on the channel side is 1 probably because of the stress ratio of the flange bolts. The bolt allowable stress does not start dropping till a high temperature.

You probably have a channel flange. There was an ASME interpretation that indicated that the bolt stress ratio should also be considered.

Best regards,
Mandeep