Highly viscous fluid 1

[sheiko]

Hi,

Do you know any standard/recommended practices about sizing relief valves for highly viscous liquids (9000 cP)?

Are API 520 or ISO 4126 applicables?

"We don't believe things because they are true, things are true because we believe them."

 

[colemanstoops]

You're pretty much on target in considering API 520. If you look at §5.8.1.4 and 5.8.1.5 of API 520 (8th edition from December 2008), you'll find a fairly explicit method for sizing relief valves for viscous liquids. A worked example problem follows immediately. That ought to step you through the procedure with minimal pain (at least, one would hope so). Speak up if I can help further.

 

[sheiko]

Thanks.

I have noticed API proposes an iterative procedure to determine the required orifice area. But in my case, i cannot find a solution. Each time i increment to a higher standard orifice size, the Reynolds number decrease and so does the Kv coefficient. As a result, i always need a bigger orifice size....until i reach the point where there is no higher standard size available.

Another point where i am lost is that the Reynolds number decrease as the orifice size increase...strange?

FYI
Pset=18 barg
total backpressure=1.7 barg
T=50 degC
Q=19 L/min
G=0.89
mu=9000 cP

"We don't believe things because they are true, things are true because we believe them."

 

[sheiko]

Please don't consider my last point on the effect of orifice size on Reynolds number.

"We don't believe things because they are true, things are true because we believe them."

 

[tjpengineer]

You must go to a DIERS approach, which resolves the Kv factor for Reynolds numbers less than 400. The API 520 Kv table/chart is useless at low Reynolds Numbers.

 

[tjpengineer]

See article attachemnt. Go to the viscous flow section.

 

[sheiko]

Thanks but i can't download the file...

"We don't believe things because they are true, things are true because we believe them."

 

[tjpengineer]

look up "SELECTION AND SIZING OF PRESSURE RELIEF VALVES"
by Randall W. Whitesides, P.E.. Its all over the net....I couldnt dowload the link either.

 

[sheiko]

Nice.

But do you know where do those correlations (Kd, Kv, ...) come from? Are they from DIERS?

"We don't believe things because they are true, things are true because we believe them."

 

[sheiko]

Any idea?

"We don't believe things because they are true, things are true because we believe them."