Mechanical Engineering, Pressure Vessel, Heat Exchanger, Risk Management, COMPRESS, MDMT, Brittle Fracture, Hydrotest randy bogard Mechanical Engineering, Pressure Vessel, Heat Exchanger, Risk Management, COMPRESS, MDMT, Brittle Fracture, Hydrotest randy bogard

Consider Longitudinal Stresses in Brittle Fracture Check

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.

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Mechanical Engineering, Pressure Vessel, Heat Exchanger, Risk Management, COMPRESS, MDMT, Hydrotest, Brittle Fracture randy bogard Mechanical Engineering, Pressure Vessel, Heat Exchanger, Risk Management, COMPRESS, MDMT, Hydrotest, Brittle Fracture randy bogard

Check Water Temperature Before Hydrotest

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.

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Mechanical Engineering, Pressure Vessel, Heat Exchanger, Risk Management, COMPRESS, Hydrotest randy bogard Mechanical Engineering, Pressure Vessel, Heat Exchanger, Risk Management, COMPRESS, Hydrotest randy bogard

Performing Proper Hydrotests After Tube Bundle Replacements

Are you performing proper hydrotests after Tube Bundle Replacements?

I’ve seen some interesting ways Owner/Operators try to save money on new equipment costs. Opting for leak tests and proof tests instead of performing ASME Code required hydrotests has become increasingly popular, especially when it comes to tube bundle replacements. The problem with not performing a full hydrotest at the fabrication shop is that the requirement to field hydrotest is hidden away as a remark at the end of the U-Form and is easily ignored. 

Owner/Operators have not yet made the connection between the frequency of their tube bundle replacements and the lack of proper hydrotest for the tube bundles they are replacing. Properly hydrotested tube bundles will last longer. The most cost effective way to perform your hydrotest is most often at the fabrication shop. Please pay your fabricator for a full hydrotest.

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