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The selection of such a fuel arrangement would be on a
drilling rig that might be drilling one month in a field where
natural gas was available and the next month out on a wildcat
where there was no gas. If it is desired to change from diesel fuel
to natural gas, the high compression ratio cylinder heads are
removed and replaced with low compression ratio heads. Larger
engines usually have a lower ratio than the smaller ones. Also fuel
pumps and injectors are removed. An intake manifold, natural gas
carburetor, and magneto are then bolted in place.
One mechanic with helper should be able to make this
conversion on one engine in about one 8-hour day. To make this
possible, some engines come with a kit containing all accessories
necessary to change over to natural gas.
The kit box is designed to handle either diesel or natural gas
accessories. In this manner, the parts not in use are stored and safe
from loss or breakage until a conversion is necessary.
Successful operation of a diesel engine depends on fuel
cleanliness more than any other one thing. Tanks and drums must
be clean. Hoses used in transferring fuel especially must be
watched. Temperatures must be kept the same as on spark plug
engines. Torque converters are also helpful on the diesel for
smooth operations.

Turbo-electric power

Gas turbines, like A.C. motors, are essentially constant-
speed machines, therefore will suited for mechanical drive of a
rotary drilling rig. Turbines though, in combination with an
electric transmission system, are a feasible means for powering a
drilling rig. Gas turbines, so called, can be fueled by either gas or
liquid hydrocarbons.
The first successful application of turbo-electric power for a
rotary rig occurred in 1965 when Continental-Emsco assembled a
3000-hp rig, referred to as Electrohoist III which used three 1100-

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