Technical Tip


  B16.9 Welding Tee

  • Sized for a design pressure of 3,000 psi
  • Operating at ambient temperature, 21°C (70°F)
  • Contains water
  • FAILS at a plant after only a few months of operation!

B31 codes in general do not talk about such situations
though B31.1 mentions it briefly for fillet welds.

How did the TEE fail?

The video clip (~6m) you came here to see is being edited for more clarity. Please see text below for the same content.

Upon investigation, the tee was found to have developed a crack along the line (see red line on the neck in the picture below) one would anticipate a max. pressure stress, not a moment stress.

The piping system was being subjected to a low pressure of 500 psi, and was cycling between 3000 psi and 500 psi two times a minute, causing a crack near the neck of the tee.



The solution recommended was to enclose the tee in a block forging (see picture above), and weld it, essentially strengthening the wall around the crack area.

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