Flow induced errosion at Tee Branch Connection

[mufasa1]

There is an Equal Tee Configuration right on the discharge line of a Boiler Feed Water Pump. The Tee branch is very close to the pump discharge, less than half a meter. The piping and fitting material is Carbon Steel. Although it is Sch 160 material, there is severe abrasion. I plan to replace the Tee connection with a Lateral, and a 45 Deg. Elbow configuration and change the Carbon Steel material to Stainless Steel material. Would be a good solution? What are your suggestions?

Thanks

 

[unclesyd]

Comeback with a little more information like flow rate, pipe sizes, temperatures, and so on.

This will help everyone visualize and understand your problem better and give a more effective recommendation.

 

[zdas04]

There are a lot of answers to that question, and all of them start with "what is the flowrate and pipe size?".

Just going to a lateral (and the other fittings that get the pipe from where it is to where you need it to be)won't necessarily eliminate the scouring that leads to abrasion.

You need to look at your fluid velocites to figure out what is going on. There are millions of pumps that discharge into the branch on a tee with no problems, you need to determine why you are having a problem before you develop a solution.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The Plural of "anecdote" is not "data"

 

[eyec]

we had a BFP that had the same problem @ a Tee & Elbow. looked like someone jsut gouged out scoops full of material.

the engineer re-fabbed the piping an moved both slightly further from the original location because of the flow rates - this was also schedule 160 6" CS pipe.

 

[SMF1964]

If you are dealing with a boiler feed pump, have you given consideration to flow accelerated corrosion (single or twho-phase). Moving the tee downstream would be a possible solution if cavitation from the pump were the primary driving factor behind the two-phase flow.

 

[JEB66]

For Flow Assisted Corrosions, a little chrome goes a long way to reducing this problem. So Stainless should help, but might not be necessary.

I would check into some other material to see if the costs and weldability might be better.

 

[zdas04]

Unclesyd,
It looks like you and I are the only ones unwilling to provide opinions with inadequate data.

David

 

[eyec]

sometimes experience with the problem provides insight where others require additional data.

 

[unclesyd]

I think zdas04 and myself have both and realize when and when not to lead with the lips.

The answers give several different options and no direction. It would be nice to present some action items for mufasa to consider, possibly in some order that might preclude an Edisonian approach.

 

[zdas04]

eyec,
Could be.

It could also be that when you've seen a half a dozen different causes for a given phenonem, you get reluctant to pick one without knowing the conditions.

Just a thought.

David

 

[eyec]

I plan to replace the Tee connection with a Lateral, and a 45 Deg. Elbow configuration and change the Carbon Steel material to Stainless Steel material. Would be a good solution? What are your suggestions?

gents,
granted, but i thought this forum was for shared ideas and experiences. not to take others to the wood shed for offering up their ideas.

he asked and some have responded.

 

[mufasa1]

Gentlemen,
Sorry for the late response. Thanks all for the comments,

Here are the necessary data:

Fluid= Boiler Feed Water
Q= 350 ton/hr (Pump discharge capacity)
T= 158.4 DegC
Discharge Pressure: 160 kg/cm2
Pipe Size= 10"
And the Tee is a 10"x6" Red. Tee, with this tee a 6" line is branched from the discharge line and the turbulence and erosion happens at this fitting.

Regards,

 

[SMF1964]

158°C=315°F (or there-about) and from what EPRI says of FAC, you are at the temperature where FAC is at its worst. You'll get some improvement with the change in geometry, but you probably would do well to upgrade the material as you've suggested. Sometimes only a slight increase in Chromium content (to, for example, SA-213 T22 material, with 2¼Cr). I would expect going to stainless steel would also help in the event that you have more of a cavitation damage than FAC and it certainly would have improved resistance to FAC (either single phase or two-phase).

Can I come out of the woodshed now?

 

[eyec]

yes the temp range is ideal for FAC as previously offered

yes adding Cr to the replacement pipe material will offer resistance to FAC as previously offered

as EPRI says, FAC is accelerated by the eddys formed near the elbows & tees as offered.

you should check/look 1.5 X pipe dia downstream of the connections for additional FAC; including the next elbow downstream.

it is a good day for all of us to be out of the woodshed

 

[bigskyguy]

Try a 10"x10"x10" tee with what ever lenth of 10" you can get on the brach outlet before you have to reduce it (10"x6" con. red) SLOW THE FLOW through the fitting. just food for thought....