| 摘要 |
A well safety valve has a valve body (105) formed by coaxial inner and outer cylindrical tubes (111, 121) and a helix (110) of at least one helix turn length tightly connecting the tubes. The valve body (105) has a fluid passage side opening (108) which is provided between the tubes, the dimensions of which are a function of the tube spacing and the helix pitch. A closure element for this opening is operated (a) permanently by a closure device (119) biasing it into a closed first position in which it closes the opening along the entire helix pitch and (b) on command by an opening device (109) which biases the closure element away from the opening with a force greater than that exerted by the closure device to allow passage of fluid under pressure. Also claimed are methods of utilising the above safety valve.
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