| 摘要 |
A well bore operating string has upper and lower wipers thereon with the wipers releasably connected by a frangible member for releasing the wipers in response to pressure in the operating string. Seals are provided to close off communication from the operating string bore to confine the pressure present in the operating string in a manner to assure release of the wipers as and when desired and in a sequence as may be desired. Upper and lower pump down plugs sealably seat, respectively, in the upper and lower wipers to form a movable, mechanical barrier to isolate or wipe ahead of and behind a substance for movement through the operating string and subsequent discharge into the well bore. The wipers are each connected to the operating string to prevent relative rotation therebetween to further reduce the possibility of malfunction or improper functioning in releasing the wipers.
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