Page 139 - Air and gas Drilling Field Guide 3rd Edition

130 CHAPTER 5 Compressors and Nitrogen Generators

(a) Surface location at sea level (SI units)
The prime mover has a maximum 261 kW available at 1800 rpm at sea level con-
ditions. The actual shaft power needed by the two-stage reciprocating compres-
2
sor to match the back pressure of 103.5 N/cm gauge is 147.9 kW. Thus, the
percent load on the prime mover, or power ratio PR is
147:9
PR ¼ ð100Þ¼ 56:7:
261
Entering the abscissa of Figure 5-16 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 3.490 N/kW-hr. The total
weight of diesel fuel consumption per hour _ w f is
_ w f ¼ 3:490ð147:9Þ¼ 516:2N=hr:

The specific gravity of diesel fuel is 0.8156 at 15.6 C [5]. The total volume (in U.S.
gallons) of diesel fuel consumption per hour q f is
516:2
q f ¼ ¼ 64:5 liters=hr;
ð0:8156Þð9:81Þ
where the specific weight of freshwater is 9.81 N/liter.

(b) Surface location at 6000 ft above sea level (USCS units)
The prime mover has a derated maximum 297.5 hp available at 1800 rpm at
6000 ft elevation. The actual shaft power needed by the two-stage reciprocating
compressor to match the back pressure of 150 psig is 175.6 hp. Thus, the percent
load on the prime mover, or power ratio PR is
175:6
PR ¼ ð100Þ¼ 59:0:
297:5
Entering the abscissa of Figure 5-16 with the power ratio percent, the approxi-
mate fuel consumption rate can be read on the ordinate using the diesel fuel
curve. The approximate fuel consumption rate at this power level is 0.580 lb/
hp-hr. The total weight of diesel fuel consumption per hour is
_ w f ¼ 0:580ð175:6Þ¼ 101:9lb=hr:
The specific gravity of diesel fuel is 0.8156, thus the total volume (in U.S. gallons)
of diesel fuel consumption per hour is
101:9
q f ¼ ¼ 15:0 gal=hr:
ð0:8156Þð8:33Þ

(b) Surface location at 1829 m above sea level (SI units)
The prime mover has a derated maximum 221.9 kW available at 1800 rpm at
1829 m elevation. The actual shaft power needed by the two-stage reciprocating