Do you consider longitudinal stresses when you check for brittle fracture?

I’ve had a lot of people asking me to check their hydrotest temperatures. A design where a governing longitudinal stress case was not considered in the Minimum Design Metal Temperature (MDMT) stood out to me. 

Did you know that longitudinal stresses can govern the MDMT even if circumferential stresses govern the Maximum Allowable Working Pressure (MAWP)? Not checking the longitudinal stresses can lead to devastating results as the brittle mode of failure is swift and catastrophic. Always remember to consider longitudinal stresses in your brittle fracture check.

Please check the water temperature before performing your hydrotest. It may be too cold! 

Have you ever seen a pressure vessel or heat exchanger crack due to brittle fracture during hydrostatic testing? Thousands of hours spent on calculations, drawings, welds, and inspections down the drain. Then the root cause investigation results in more time and money lost. 
Brittle fracture can occur during hydrostatic testing when the water temperature used in the hydrotest is too close to the Minimum Design Metal Temperature (MDMT) of the material. This means that your equipment can pass the design MDMT calculations and still experience brittle fracture during hydrostatic testing. This simple temperature check is often missed and can lead to devastating results.

Please review UG-99 for more information regarding hydrostatic testing.