Thermal fatigue cracking is a potentially dangerous condition that occurs as a result of cyclical expansion and contraction caused by temperature variations in industrial process equipment. The extent of damage will depend on the frequency and magnitude of these temperature swings. Damage from thermal fatigue manifests itself in the form of cracking in the equipment material. Cracks start on the surface and can propagate through the material, causing structural failure.
Managing Thermal Fatigue Cracking
Steps can be taken in vessel design and plant operation to reduce the effects of thermal fatigue cracking. For instance, temperature gradients can be decreased by controlling process parameters to reduce rates of heating or cooling. In some applications, vessels can be lined to diminish the thermal shock between process fluid and the equipment material. Non-destructive testing techniques can be employed to detect the extent of thermal cracking as well. Some of these include liquid penetrant testing, magnetic particle testing, and ultrasonic testing.
Consequences of Failure
When thermal fatigue cracking goes unmanaged, there is an increased risk of pressure vessel rupture, which can have catastrophic results. In the past, such incidents have led to severe injuries and fatalities among plant operators, as well as extensive damage to pieces of equipment from tank projectiles. Less serious failures may include leaks, which can create hazardous conditions, especially if the tank contains flammable and/or volatile substances.
Pressure Vessel Certification
Today, pressure vessels are designed and fabricated to the ASME Section VIII code. These are strict guidelines put in place to minimize the risk of thermal fatigue and prevent structural failure. Pressure vessels built to this standard carry an official U stamp, indicating conformance to code from an authorized ASME inspector.
To reduce the risk of thermal fatigue cracking to your manufacturing plant and operators, it’s important to engage with a reputable and certified fabricator of pressure vessels.