Wear in fittings 1

[MechP]

Hello everyone,
What is your advice with respect to erosive wear in a tee fitting when the flow is directed into the tee through the branch? In other words, the branch of the tee is not deriving the flow but rather the entire flow enters through the branch and splits almost equally along both in-line sides of the fitting. Of course it depends on what's flowing and the velocity, but under what circumstances could it generate an accelerated wear with respect to the pipe in general?

 

[pennpiper]

juanjogo,
Do you have a specific problem you are dealing with or you working on a class project?
Do you have a specific Commodity?
Do you have a specific material for your piping system?
Do you have a specific operating temperature?
Do you have a specific Pressure and flow speed?
Do you have any "Grit" (like sand) in the flow liquid?
Do you have a pipe size for this system?
Do you have any other important information about this problem that we should know?

Sometimes its possible to do all the right things and still get bad results

 

[MechP]

Hello pennpiper,
I wanted to know if its a good practice in general, but in my case specifically the conditions are as follows:

- Fluid: water for well injection (a minimum amount of grit material could be present)
- Temperature: 100°F
- Pressure: 1500 psi
- NPS: 6"
- Velocity: 7.7 fps
- Code: B31.4
- Fitting material: ASTM A860 WPHY70, SCH 40

Thanks for your reply

 

[Dhurjati Sen]

Dear juanjogo,

This material is normally used everywhere and is absolutely fine in your case. However, regarding thickness (schedule 40 or higher) consult your piping engineer.

Regarding flow control and thereby preventing erosion, of course increasing the schedule is the worst method.

Regards.

DHURJATI SEN
Kolkata, India

 

[gerhardl]

If we neglect the pressure difference and flow characteristics caused by the T (one 6" inlet T with 2x6" outlet?) and look at the flow speed only we have 7,7 fps flow in (2,34 m/s) and 3,85fps (1,17 m/s) in each of the T branches out.

A normal, laminar flow under this conditions, should give a minimum of wear. The question is if the redistribution gives turbulent flow or cavitation in any part of the T. My guess is that it probably is acceptable conditions and should give a normal wear, but a guess only!

 

[MJCronin]

I disagree with Mr. Sen above... In my opinion:

If erosion by particles is suspected as being the cause of the problem, you have IMHO the following options:

- Use of a more erosion resistant piping material such as 304/316 stainless steel or alloy steel
- Increase the fitting schedule to 80/XS
- Install a 3/8 thick SS "target" plate within the tee
- Explore a urethane erosion resistant internal coating, typically used in slurry piping service




MJCronin
Sr. Process Engineer

 

[MechP]

Thank you all for your replies.
Gerharld has a good point bringing up possible cavitation. It seems unlikely due to the high pressure and low speed; still, I’ve seen some papers available on the subject. I’ll check them out.

 

[LittleInch]

In general you should avoid flow into a tee from a branch of there is any chance of erosive material. You can very easily bore a hole in the tee.

Far better to use a target tee or cushion tee wuth a second tee for your other flow path.

This sends the sand into the dead end.

Like this

http://www.flangesfittings.com/cushion-tee.html

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[KevinNZ]

I agree with LittleInch. Sending the flow into the dead end of a tee does work. We had flow from wells that regularly worn holes in elbows and replacing with a tee fixed the problem.

 

[Gator]

There are also cushion crosses but I bet they are quite difficult to get.

 

[LittleInch]

Or buy a Cross and just weld a cap on the end or a flange and thick blank flange opposite the incoming branch.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[MechP]

This is great advice. I'm not sure if supply of cushion tees can meet the procurement deadline, so I'll go with LittleInch's last advice.
Thank you

 

[LittleInch]

If you go this route make the cap sch 160.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.