Critical Joints

Critical joints are joints that are typically more difficult to seal, joints that have a history of leakage, or joints where leaks could result in high consequence incidents due to their size and/or service conditions.

Creating Critical Joints

Critical Joint status is assigned when creating Flange-FLOCs. To flag a Flange-FLOC as a Critical Joint:

When creating a new Flange-FLOC:

• Ensure that the Critical Joint checkbox is selected when Creating Flange-FLOCs.

• Fill in any other mandatory fields.

• Click Save.

Flagging an existing Flange-FLOC as a Critical Joint

• Open the Flange-FLOC Details Page.

• Click Edit in the header section of the Flange-FLOC.

• Check the Critical Joint checkbox.

• Click Save.

Note

When a Flange-FLOC has been flagged as a Critical Joint, all Equipment with that Flange FLOC as a parent will inherit the Critical Joint flag. Critical Joint status cannot be set on the Equipment Level.

Examples of Critical Joints

Some examples of Critical Joints include:

• Joints in highly hazardous chemical service.

• Flange sizes NPS 6 (DN 150) and greater, class 600 and greater in hydrogen service, with an

  operating temperature above 600°F (315°C).

• Flange sizes NPS 8 (DN 200) and greater, class 900 in hydrocarbon or sour service, with an

  operating temperature above 600°F (315°C).

• Flange sizes NPS 6 (DN 150) and greater, class 1500 in hydrocarbon or sour service, with an

  operating temperature above 600°F (315°C).

• Flange sizes NPS 4 (DN 100) and greater, class 2500 in hydrocarbon or sour service, with an

  operating temperature above 600°F (315°C).

• Flanged connections with a history of leakage (also known as “bad actor flanges”).

• Joints of a unique or unusual design (e.g. connections between aluminium and stainless steel flanges on a cold box heat exchanger).

Critical joints require hydraulic tensioning or controlled bolt torquing with new studs and nuts every time the joint is disturbed to provide additional assurance the proper bolt assembly stress is achieved.

All critical joints with an operating temperature greater than 500°F (260°F) should be hot torqued (start-up retorque) during the first start-up after initial assembly.