Page 141 - Air and gas Drilling Field Guide 3rd Edition

132 CHAPTER 5 Compressors and Nitrogen Generators

compressor to produce the fixed design pressure of 206.9 N/cm 2 gauge is
183.9 kW. Thus, the percent load on the prime mover, or power ratio PR is
183:9
PR ¼ ð100Þ¼ 70:5:
261
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 3.191
N/kW-hr. The total weight of diesel fuel consumption per hour _ w f is
_ w f ¼ 3:191ð183:9Þ¼ 587:0N=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
587:0
q f ¼ ¼ 73:4 liters=hr;
ð0:8156Þð9:81Þ
where the specific weight of fresh water is 9.81 N/liter.
(b) Surface location at 6000 ft above sea level (USCS units)
The prime mover has a maximum 297.5 hp available at 1800 rpm at sea level con-
ditions. The actual shaft power needed by the two-stage helical lobe (screw) com-
pressor to produce the fixed design pressure of 240.2 psig is 197.5 hp. Thus, the
percent load on the prime mover, or power ratio PR is
197:5
PR ¼ ð100Þ¼ 66:4:
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 0.550 lb/
hp-hr. The total weight of diesel fuel consumption per hour is
_ w f ¼ 0:550ð197:5Þ¼ 108:6lb=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
108:6
q f ¼ ¼ 16:0 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 helical
lobe (screw) compressor to produce the fixed design pressure of 173.8 N/cm 2
gauge is 147.3 kW. Thus, the percent load on the prime mover, or power ratio
PR is