Steam pipe thrust calculation

[Clymber]

I'm trying to calculate the thrust load on a 3" HPS elbow, Sch. 80, welded construction, for an underground direct-bury application. I don't typically work with steam, so I'd like a check of my numbers.

This is a 3" branch pipe off an 8" HPS main at 175 PSIG. Design velocity is 5000 FPS.

The equation asks for fluid SG, pipe ID, velocity, angle of bend, and gauge pressure. Using a saturated vapor density of 0.38408 LBM/FT3, I get a SG of 0.006152. Is this correct?
Plugging the other values into the equation yields:

Are these numbers accurate? 20,000 LBF seems like a lot for a 3" pipe.

Calculations based on this page: Link

Thanks in advance for checking my work.
-Clymber

 

[LittleInch]

Err, start with your velocity - 5 Thousand Feet per second???? I don't think rocket engines go that fast.

That's 3 times the speed of sound.

Not surprised there's 10 tonnes force on your 3" elbow.

Anyway, if its buried and a fully welded system, what's your issue?

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[ione]

Maybe 5000 fpm.....

http://www.engineeringtoolbox.com/forces-pipe-bends-d_968.html

 

[Clymber]

Good catch. FPS is correct.

 

[LittleInch]

Sorry, but which one is correct fps or fpm??

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

 

[DSB123]

as LittleInch asks - If it buried and fully welded - what is the issue? Why do you want to know what the bend thrust load is? Are you sure the "Steam" pipe is buried?

 

[LittleInch]

Also if it is 5000fps how are you managing to get 3 times as much flow as choked flow? List all the proper data and we might get somewhere

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

 

[BigInch]

5000 fps won't last long. That will dissolve the pipe.

 

[BronYrAur]

Are you really looking for velocity thrust or thermal expansion? Need to know more about the locations of expansion joints and anchors.

 

[georgeverghese]

There's something odd about the input in the calculator in the link - the metric input asks for a fluid density, but not the US units input. It looks like the US input section would work only for liquids - there isnt enough input for it to work out gas density.

 

[DSB123]

BronYrAur,
Please advise where the OP mentions expansion joints or indeed anchors? Also the OP makes no reference to thermal expansion considerations. Don't read things into a question which are not there!

 

[chicopee]

I agree with IONE steam flow speed at 5000 fpm. The recommended steam flow speeds are 5,000 fpm for heating service; 10,000 fpm for high pressure saturated steam; and 14,000 to 20,000 fpm for high pressure superheated steam.

 

[LittleInch]

It would appear that now the OP has input the correct data and hence got the correct output he or she has disappeared without trace. .. Or thanks or feedback...

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