Page 256 - Petroleum and Gas Field Processing

Equating Eqs. (21) and (24),
Q pw h pw
HWL ¼ 4:824 ð25Þ
ð

Þd cos
w
o
m
For efficient settling of the oil droplets, it has been reported that the
Reynolds number (Re) with the characteristic dimension being four times
the hydraulic radius should not exceed 1600. This can be used to develop
an equation for the minimum flow area (HW ) as follows. The hydraulic
radius, R, is obtained by dividing the area between plates by the wetted
perimeter, that is,

ðh=12ÞðW= cos Þ
R ¼
ð
2 ðW= cos Þþðh=12ÞÞ
ðh=12Þ
R ¼
2ð1 þðh cos =12W ÞÞ
Considering that (h cos /12) W, R may be approximated by
h
R ¼
24
Therefore,

w Du w
Re ¼ ¼ 1600
g
2
where g is the acceleration of gravity, ft/sec . Substituting for u w from Eq.
3
(23), D ¼ 4R, w ¼ 62.4
w lb/ft , and ¼ 2.088 10 5 pw and solving for
HW, we obtain
Q h
4 pw w 2
HW ¼ 6:982 10 ft ð26Þ
pw
Equation (26) is first used to determine the minimum value of HW, then
Eq. (25) is used to determine L for any value of HW above the minimum
determined.

9.6.5 Sizing of Skimmers with CPI
The corrugated plate interceptor packs are normally available in standard

sizes with H ¼ 3.25 ft, W ¼ 3.25 ft, L ¼ 5.75 ft, h ¼ 0.69 in., and ¼ 45 . The
size of the skimmer used with the CPI is determined by the number of CPI
packs installed. It should be noted that the flow rate through the standard
CPI pack should not exceed 20,000 BPD in order to stay within the
Reynolds number limitation.

Copyright 2003 by Marcel Dekker, Inc. All Rights Reserved.