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Although initial closure of the<br />
packing unit is obtained by<br />
hydraulic pressure from an<br />
external source, well<br />
pressure will increase sealing<br />
effect and thus insure<br />
positive closure under high<br />
well pressure.<br />
The preventer is normally<br />
operated by a fluid pressure<br />
of 103 10 5 Pa (1500 psi).<br />
A pressure regulator should be<br />
employed to insure the lowest<br />
closing pressure to permit<br />
slight leakage of well fluid<br />
around the drill pipe when<br />
rotating or stripping in or out of<br />
the hole.<br />
A small amount of fluid leaking<br />
past the pipe will lubricate and<br />
cool the packing unit.<br />
Annular-type<br />
preventer (Hydril)
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