Blowdown pipe erosion

[bepalo]

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?

 

[metengr]

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

 

[EdStainless]

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

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P.E. Metallurgy, Plymouth Tube

 

[chicopee]

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.

 

[georgeverghese]

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.

 

[MJCronin]

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

 

[metengr]

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

 

[MJCronin]

http://www.eng-tips.com/viewthread.cfm?qid=334845

MJCronin
Sr. Process Engineer