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 TABLE 5-3.
Pressure Test Data
Pressure
Time
(min:sec)
(psig)
90
0:00
80
10:42
70
23:17
60
38:34
50
58:56
40
87: 28
30
135:01
TABLE 5-4.
C a l c u l a t i o n of Losses
Average
Pressure
Pressure
Time
Loss
Time
(psig)
(psig) (min:sec)
(rein)
(scfm)
90--80
85
40
10:42
10.70
80-70
75
34
23:17
23.28
70-60
28
65
38:34
38.57
60-50
55
21
58:56
58.93
50-40
45
15
87:28
87.47
40-30
35
135:01
9
135.02
30-20
3
25
277:40
277.67
(f) Applying linear regression to the data:
x = avg press.
Y = loss
Y = mX+b
y i e l d s the equation: Q = 0.62 P - 12.75.
L o s s e s at operating or nominal pressure (96 psig) are calculated:
Q 9 6 = O . 6 2 (96) - 12.75
47 scfm
Q
=
96
A t a cost of 50 cents for 1,000 cubic feet of compressed air,
t h i s represents: $ 1 2 , 3 5 0 / y e a r (dollar figure will vary based on
f a c i l i t y costs for compressed air).
6 CORRECTIVE MEASURES. Q n o m i n a l r e p r e s e n t s t h e l o s s i n t h e c o m p r e s s e d a i r
s y s t e m at operating conditions, assuming a constant pressure over the length
o f pipe in question. T h i s value, taken with the activity's cost to produce
c o m p r e s s e d air, can be used to develop projects to repair or replace sections
o f compressed air line.
5-20
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