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Usually, the air-bottle assembly will consist of six air-pressure bottles and

associated valves, each bottle containing approximately 25 cu ft of air. The bottles

are interconnected. Using an air-operated isolation valve, remotely controlled from

the driller's control panel, allows up to 60% of the operating bottle volume to be

isolated temporarily. This eliminates the need to reduce the entire system pressure
to perform operations requiring significantly reduced pressure.

At full capacity, the fluid supply unit storage reservoir contains 395 gal of
hydraulic fluid. Also included are two air/oil pumps, a filtering system, and a fluid

sensing system. The fluid sensing system automatically maintains the hydraulic
fluid level of the accumulator at a safe level by pumping the hydraulic fluid back

into the system when required.

It is important to use a hydraulic fluid with excellent physical properties

with respect to viscosity and sensitivity to changes in temperatures.

The air supply system should consist of two or more air compressors and

associated dryers to provide dry, high-pressure air to the system (3,500 psi). One or

more air storage bottles ensure a ready supply of high-pressure air to both the

motion compensator and tensioner systems. Operating controls and indicators are

installed on the driller's control panel located on the drilling floor. This enables the

driller to operate and monitor the entire motion compensator system. The manually

operated controls open and close the valves, adjust the operating system pressure to

the operating load, and raise or lower the isolated system pressure. Large, easy-to-

read gauges display the various system pressure readings, and indicators show the

lock pin position and piston rod(s) extension.

A motion compensator system functions as a hydraulically loaded tension

spring with an adjustable tension effort. The compensator's hydraulic operating

system is passive. Rather than being driven by hydraulic pumps, the system is

energized by a compressed air supply system that acts on a given amount of

hydraulic fluid by means of an accumulator. Ideally, the volume of fluid never

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