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Spring-loaded float valves<br />
The spring-loaded ball, or dart, and seat float valve offers<br />
the advantage of an instantaneous and positive shut off<br />
of backflow through the drill string.<br />
These valves are not full-bore and thus cannot sustain long<br />
duration or high volume pumping of drilling or kill fluid.<br />
A wireline retrievable valve that seals in a profiled body that has<br />
an opening approximately the same inside diameter as that of<br />
tool joint may be used to provide a full-open access, if needed.
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