Multiple Inline Restriction Let-Down Orifices 4

[rzrbk]

In a case where a restriction orifice will be used in a minimum flow line for a pump, is there a rule-of-thumb way to determine 1)if more than one orifice is needed, and 2)about how many stages are required?

For example, there is a charge pump application where the discharge side of the orifice will be at 860 psig and suction side at 35 psig. (straight run diesel at 380degF, say 0.70 SG at FTP and vapor pressure of 9.0psia)
Feels like a situation where multiple orifices may be needed, but would like to be able to confirm and estimate how many.

Thanks in advance for any help.

 

[TD2K]

I would definitely expect to see cavitation through a single RO with those conditions (I'm trying to decide if this cavitation would bother me if it was going back to say a tank wrt line erosion, I'm not sure).

In any event, as an alternative, this is a paper on sizing muliple orifices. Essentially, you size the last orifice first such that the pressure in the vena contra just reaches the vapor pressure of the fluid. Then the next one is sized and so on up the line so you never have cavitation. The paper also includes how far apart to space each orifice.

http://s15.yousendit.com/d.aspx?id=30TMEAHFUBB5R1P2RFPB8IGBLN

 

[EGT01]

TD2K,

Maybe I live a sheltered life but I find your link method to be as interersting as the article. By the way, the article looks like it came from Chemical Engineering magazine, can you give the details of the publication (journal, date, etc).

 

[TD2K]

I thought it was also a great service to book mark when I came across it EGT01. Now that Yahoo and Hotmail handles larger files since Google started their email service it's not as critical. However, it's also a good way to avoid posting email addresses on the site which Eng-Tips prefers you don't. On the downside, the link is only good for a limited period of time.

Let me take a look at my copy at home EGT01. It's from quite a while back, I saved it when I was working at the AGEC ethylene plants in Red Deer, AB so that's pushing 20 years ago. It was written by a couple of people working for Ontario Hydro at the time.

 

[stanier]

Heve you considered the use of a microturbine to recover the energy without the risks associated with cavitating (vapourising ) diesel?

 

[TD2K]

ETG01, dug up the original copy. Unfortunately, when I copied it I didn't position the magazine properly to get that bottom of the page with that information.

 

[katmar]

The Tung and Mikasinovic article is from Chemical Engineering, December 12, 1983, pgs 69-71.

See also Lin S.H. Hydrocarbon Processing, July 1985, pgs 93-95

 

[unclesyd]

You can probably get both articles at the following site for a nominal fee.

http://www.lindahall.org/