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valve is set to the 'Pump' position movement of the tank assembly relative to the elevation tube causes the
ram cylinder to operate as a pump. When the tank assembly is raised air at atmospheric pressure is drawn
into the ram cylinder through a non-return valve in the head of the piston. During the downstroke the air is
compressed by the piston and admitted to the tank through the non-return valve in the tank top plate to build
up pneumatic pressure.
16
A steering ring
is located at the top of the tank assembly. It may, as its name suggests, be used for
steering the pedestal, but is intended primarily for use as a handle, when pressurizing the pedestal or altering
its height (
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The safety latch
and control valve are located close to the steering ring and are positioned in such a
way as to minimise the risk of accidental operation.