Page 143 - Air and gas Drilling Field Guide 3rd Edition

134 CHAPTER 5 Compressors and Nitrogen Generators

5.7 EXAMPLE COMPRESSOR SYSTEM UNITS
In this section, several operational example compressor system units are pre-
sented. These units represent the typical variety of units in operation around
the United States and the world. In follow-on illustrative examples for air and
gas drilling operations, stable foam drilling operations, and aerated fluid drilling
operations, one or more of these compressor system units will be used as the pro-
vider of the compressed air or gas.
It must be understood that all primary compressors are specified by (1) the
volumetric flow rate of atmospheric air that they intake and (2) the maximum
output pressure that they can exhaust.
The atmospheric air volumetric flow rate intake capability is given as acfm
(actual cubic feet per minute) or as actual liters/second. This primary compres-
sor specification recognizes that the actual internal design of a positive displace-
ment compressor cannot be altered as the machine is moved from one surface
location above sea level to another (i.e., the internal volume chambers cannot
be altered). Primary compressors intake their specified volumetric flow rate of
the atmospheric air regardless where that location is above sea level. The maxi-
mum output pressure specification pertains to a structural design limitation on
the housing and moving parts of the positive displacement compressor.
Booster compressors are specified by (1) the minimum pressure limit of the
compressed air the booster will accept from the primary compressors, (2) the
intake volumetric flow rate (at that minimum pressure limit) in scfm (standard
cubic feet per minute) or standard liters/second, and (3) the maximum pressure
output capability of the booster.
The minimum intake pressure limit and its volumetric flow rate are related to
the restriction on available booster suction power. The output pressure limit is
related to the structural design limitations of the booster.

5.7.1 Small Reciprocating Primary and Booster Compressor System
Most of the compressor systems for air and gas drilling operations are provided as
a separate primary compressor system unit (either with a reciprocating compres-
sor or with a rotary compressor) and a separate booster compressor system unit
(always a reciprocating compressor). These units are usually skid mounted and
each has its own prime mover.
Figure 5-18 shows a skid-mounted primary compressor system unit that has a
Gardner Denver Model WEN, two-stage reciprocating piston compressor. The
Gardner Denver Model WEN is operated at 1000 rpm. At this speed, the compres-
sor has a volumetric flow rate of 700 acfm (330 actual liters/sec) and a maximum
2
pressure capability of 350 psig (241 N/cm gauge) at API Mechanical Equipment
Standards. The compressor and its cooling subsystem are shown at the right
end of the skid in Figure 5-18. On the left end of the skid in Figure 5-18 is the
Caterpillar Model D353 prime mover. The Caterpillar Model D353 is an in-line
six cylinder, diesel-fueled prime mover. This prime mover is turbocharged and