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Blowdown pipe erosion

Blowdown pipe erosion

(OP)
Have a surface blowndown line 1" in dia. It tees into a 2" forged steel tee. Boiler pressure is about 100 psi. The eroded spot is directly above the tee and the reducer from 1" to 2" is about 6" prior to the tee. Downstream it leads to a drain. The failure occurred after approximately 18 months. I'm suspecting mechanical erosion, does anyone else have any thoughts on the failure?

RE: Blowdown pipe erosion

Yes this can be typical for carbon steel blowdown lines. You need a more direct path for blow down versus a Tee.

RE: Blowdown pipe erosion

You also need an alloy with higher Cr, maybe 2.5%.
Combine this with improved flow path and you will never repair this again.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Blowdown pipe erosion

Nothing unusual about metal erosion in blowdown connections. A certified welder whose firm has a valid NB Repair stamp will have to go inside the steam drum to repair.

RE: Blowdown pipe erosion

Could this location be a low point in the flowpath where condensate could have collected ? Vapor blowdown lines should always be free draining, including any dead ends.

RE: Blowdown pipe erosion

Ed Stainless is spot-on ....

For several fossil projects, I have seen blowdown piping configured with a sacrificial erosion "target".

Schedule 80 Low alloy material (A335-P22)was commonly used.

316 Stainless steel piping can also be used....

MJCronin
Sr. Process Engineer

RE: Blowdown pipe erosion

Just replace the reconfigured blow down piping with Grade P22 or even a Grade P5 material.

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