Page 137 - Air and Gas Drilling Manual

Chapter 4: Compressors 4-23
these units can be single stage, or multistage. The prime movers for these units can
be fueled by gasoline, propane/butane, diesel, or natural gas. These units can be
fabricated as skid mounted, semi-trailer mounted, or as wheeled trailers.

Figure 4-15: Prime mover percentage reduction in power as a function of elevation above
sea level [1].
Booster Compressor System Unit
Booster compressor system units are operated downstream from a primary
compressor system (sometimes these units are denoted as secondary units). They
accept compressed air from the primary compressor system and compress the air to a
higher pressure before sending the air to the drilling rig. Also, a booster compressor
system can accept compressed natural gas (or other gases) from a pipeline and
compress that gas to a higher pressure before sending the gas to the drilling rig. The
compressors in these units are all reciprocating compressors. The compressors in
these units can be single stage, or multistage. The prime movers for these units can
be fueled by gasoline, propane/butane, diesel, or natural gas. These units can be
fabricated as skid mounted, semi-trailer mounted, or as wheeled trailers.

4.6.2 Reciprocating Compressor Unit
A reciprocating compressor can adjust its output pressure to match the back-
pressure on the machine. Thus, the reciprocating compressor is somewhat more
flexible than the rotary compressor and will tend to use less fuel for a given
application than a similarly configured rotary compressor [1, 11].
The intake volumetric flow rate of a real reciprocating compressor is slightly
smaller than the theoretical sweep volume (i.e., the calculated intake volumetric flow
rate). This is due to the fact that the piston compressor cannot be fabricated without
a clearance volume. This clearance volume at the top of the piston cylinder is
necessary in order to have space for the valves and to keep the piston from striking