RO vs. small pipe to restrict flow

[BenThayer]

doing a quick sanity check here.

we need to restrict the flow for a given situation. there is concern that we may not be able to adequately clean between batches if we use the typical restriction orifice and so we were considering reducing the line size.

so for a given restriction of 100 gpm and 50 psi pressure drop, we are expecting an orifice of about 0.88 inches.

but if we try to extrapolate dP for a typical line size, we get 100 gpm giving us ~50.5 psig dP in ~1.4 feet of 1/2" sch 40 pipe (ID = 0.622")

note that example calcs are for water, s.g. of 1.0

Why the difference? Bad assumptions or recoverable pressure drop coming into play?

thanks, ben

 

[Latexman]

Add an entrance and exit to that 1/2" line and see what happens. dP > 150 psi! Are you comparing apples to apples?

Good luck,
Latexman

 

[CJKruger]

BenThayer, the results from Korf Hydraulics is (assuming 4" connecting pipes):

1) Restriction orifice is 0.87".

2) For a pipe of 0.87", you need 3.5 ft.

3) For a 1/2" Sch 40 pipe, the flow is only 68 gpm even if the pipe length is zero (reduced + expander only).

 

[saiedmehdipour]

Hi Dear All,
would you please tell me why shall be connect direct mounted level transmitter with ESD signal to vessel and no permition to inestall LT with ESD signal on stand pipe on vessel.

 

[Artisi]

saiedmehdipour

Re-post your question under a new heading if you expect an answer.

 

[davefitz]

using a "capillary tube " is a conservative way to provide a flow restriction- if sized properly and correct matierial is selected, it can last far longer than an orifice, and does not have teh erosion or noise issues of a single orifice.

Entrance and exit losses must be included, and the velocity near the inlet "vena contracta" may be on the order of 1.6 times the average tube developed flow velocity. So the material selection is based on that velocity near the inlet. Typical rAnge of allowable velocities for some materials in water service may be :
CS- not to exceed 20 fps local
1% chrome alloy- not to exceed 27 fps local
SS or incolnel - not to exceed 75 fps local