Losses through Tee Run when Branch is blanked.

[steveb1111]

On a 2-inch inlet line to a PSV we have an installed Tee fitting with a blanked vent valve taken off the Tee branch.

The equivalent length of a Straight through Tee is dominating the friction losses in the PSV inlet line generating losses exceeding API 3% guideline.

If there is no flow to or from the branch, can we discount loss through the run.

 

[CJKruger]

steveb1111, I think this is a good question. My opinion is:

- Most people will simply use the L/D or K value from Crane. K value is roughly 0.3.

- If the Crane value works (dP<3%), then no problem.

- However, if it does not, then I think you can reduce it.

- Based on other references, I think the real K value (with zero flow thru branch), is between 0 and 0.1.

 

[Latexman]

We use K = 0.1 for a line run T. It's conservative.

Good luck,
Latexman

 

[BigInch]

Steve, where are your two points located that you are using to get the pressure drop?

**********************
"Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic
"Note: Make that 99.99% for pipeline companies" -

http://virtualpipeline.spaces.live.com/

 

[katmar]

The OP has not stated whether this is a threaded or welded tee. The Crane data does not specifically say that it is for threaded tees only, but the diagram implies that it does. For a 2" tee Crane gives K=0.38

Both Hooper and Darby do distinguish between threaded and welded tees, but give conflicting values. For a 2" tee with a Reynolds number of 150,000 Darby's 3-K method gives 0.39 for a threaded tee and 0.07 for a welded tee. This trend is reversed by Hooper's 2-K method which gives 0.1 for the threaded tee and 0.5 for the welded one. Does anyone know if this was an error in the original Hooper article (Chem Eng, Aug 24, 1981)? Maybe a correction was published later?

The Hydraulic Institute data (quoted by Simpson, Chem Eng, April 3, 1978) indicates that the threaded tee has a significantly higher K value that does the welded tee. This makes me think that maybe Hooper mixed up his constants between the two types of tees.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[steveb1111]

Thanks for your responses.

It's a welded, 2 x 3/4 inch reducing Tee.

 

[steveb1111]

To Big Inch. The 2-in PSV inlet is taken off a 2-in process line. The pressure drop is taken from entrance to the 2-in inlet to the PSV inlet flange.

On other PSVs with larger inlets, the inlet vent valve is fitted onto a Nipoflange and issue of a Tee doesn't arise (no Tee has been allowed for in hydraulic calc). It's only because the isometric indicates a Tee fitting for the 2-in inlet vent valve that the TEE has been included.

My preference would be to ignore the TEE loss in this instance.

 

[BigInch]

Actually I think I would too.

**********************
"Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic
"Note: Make that 99.99% for pipeline companies" -

http://virtualpipeline.spaces.live.com/