Page 146 - Air and Gas Drilling Manual

4-32 Air and Gas Drilling Manual
190 4 .
PR =
) = 63 5.
(100
300
Entering the abscissa of Figure 4-17 with the power ratio percent, the approximate
fuel consumption rate can be read on the ordinate using the diesel fuel curve. The
approximate fuel consumption rate at this power level is 0.560 lb/hp-hr. The total
weight of diesel fuel consumption per hour, ˙ w , is
f
˙ w = 0 .560 (190 . ) =4 106 .6 lb/hr
f
The specific gravity of diesel fuel is 0.8156 at 60˚F [5]. The total volume (in
United States gallons) of diesel fuel consumption per hour, q , is
f
q f = 106 6 . = 15 7 . gal/hr
.
.
(0 8156 )(8 33 )
where the specific weight of fresh water is 8.33 lb/gal.
b) Surface location at 6,000 ft above sea level.
The prime mover has a derated maximum 234 horsepower available at 1,000
rpm at 6,000 ft elevation. The actual shaft power needed by the three-stage
reciprocating compressor to match the back-pressure of 150 psig is 168.2
horsepower. Thus, the percent load on the prime mover, or power ratio is
PR = 168 2 . (100 ) = 71 9.
234

Entering the abscissa of Figure 4-17 with the power ratio percent, the approximate
fuel consumption rate can be read on the ordinate using the diesel fuel curve. The
approximate fuel consumption rate at this power level is 0.538 lb/hp-hr. The total
weight of diesel fuel consumption per hour is

˙ w = 0 .538 (168 . ) =2 90 .5 lb/hr
f
The specific gravity of diesel fuel is 0.8156, thus, the total volume (in United States
gallons) of diesel fuel consumption per hour is
.
q f = 90 5 = 13 2 gal/hr
.
(0 8156. )(8 33. )
Illustrative Example 4.4 Determine the diesel fuel consumption rate (in
gallons per hour) for the on-board Sullair Model 840 primary rotary screw
compressor system. Carry out these calculations for the two surface drilling
locations given in Illustrative Example 4.2. These are, a) a surface location at sea
level and, b) a surface location elevation of 6,000 ft).