Page 153 - Air and Gas Drilling Manual

Chapter 4: Compressors 4-39

Figure 4-23: Skid mounted reciprocating piston booster compressor system unit
(courtesy of Mountain Air Drilling Service).

4.7.3 Rotary Primary and Reciprocating Compressor System
The compressor system unit shown in Figure 4-24 is an unusual design. It is a
semi-trailer mounted unit that has both primary compressor and booster compressor
driven by one large prime mover. The prime mover drives the primary compressor
through a gear box that steps the speed up the primary. The booster compressor is
drive directly at the speed of the prime mover.
The primary compressor is a MAN (German manufacture) Model GHH-
CF246G, single-stage, oil flooded, rotary helical lobe (screw) compressor. The
helical lobe compressor is driven at 1,969 rpm by the prime mover which is rotating
1,800 rpm. A gearbox with a 1.094 ratio connects the primary to the prime mover.
At a rotation speed of 1,969 rpm the helical lobe compressor has a volumetric flow
rate of 1,727 scfm and produces a fixed pressure discharge of 190 psig at ASME
Standards standard conditions. There is a discharge mechanical adjustment that can
be made that will allow a 210 psig fixed pressure discharge but with a slightly lower
corresponding volumetric flow rate.
The booster compressor is an Ariel Model JGJ/2, a two-stage, reciprocating
piston compressor. Figure 4-24 shows the cooling subsystem at the front end (hitch
end) of the trailer mounted unit. This cooling subsystem is the aftercooler for the
primary compressor, the innercooler between the first and second stage of the booster,
the aftercooler for the booster, and the cooling system for the prime mover. Next is
the primary compressor (with the gearbox between it and the prime mover shaft).
The prime mover located next to the cooling subsystem (toward the aft end of
the trailer unit). At the aft end of the trailer is the booster compressor. The prime
mover for this unit is a Caterpillar Model 3412. This prime mover has a V-12 piston
configuration. The prime mover is diesel fueled, turbocharged and aftercooled. The
prime mover is operated at a speed of 1,800 rpm and at that speed can produce a
peak 740 horsepower (at API Mechanical Equipment Standards standard conditions).