Wells – Submerged well – Connection or disconnection of submerged members remotely...
Reexamination Certificate
2000-04-03
2001-08-28
Tsay, Frank S. (Department: 3672)
Wells
Submerged well
Connection or disconnection of submerged members remotely...
C166S242100, C138S103000
Reexamination Certificate
active
06279661
ABSTRACT:
This invention pertains to pierced plates called pad eyes which are normally welded to tubular goods used in earth bore holes, and other structural members, handled by lifting apparatus.
BACKGROUND
Pad eyes are normally attached by welding to at least one end of tubular goods. At least two pad eyes are used diametrically opposite, within several inches of the end of the tube. After they have served the intended function, the pad eyes are often cut away. The pad eyes are critical elements in that they may temporarily support a full length of well bore related pipe. Their strength is a matter of concern and they are usually certified capable of the load expected.
When in the vertical position the load is usually supported by a wire line, or bail, attached to the pad eye by a clevis and pin. The hole in the pad eye has to be somewhat larger than the pin to enable the pin to be inserted without much time loss. A pin in an oversize hole, when lifting along a vector transverse to the pin axis, engages the hole wall along a line. At the line the unit loads are often very high and exceed the yield strength of the pad eye material. Large loads deform the material until an area of engagement on the pin distributes the stress to an amount below the yield strength of the pad eye material. The pin is harder than the pad eye and deforms very little. A deformed pin could not be easily pulled back through the clevis eye.
A considerable amount of engineering goes into certification of the pad eye but little is known about the stress distribution in metal around a deformed hole. The deformed metal around a hole presents a complex mathematical shape relationship to the parent metal. Metal crack resistance is suspect in the presence of work hardening that attends deformation. The prospect of dropping a string of casing, tubing, or conductor pipe into a hole is a matter that few engineers can ignore. through the clevis and the pad eye hole. The holes are currently made larger than the pin to avoid loss of time in rigging up for lifting. Making the hole, in total, fit the pin is not practical but making it larger, for utility, gives rise to the problem presently addressed.
SUMMARY OF INVENTION
A pad eye is provided with an arc that corresponds to the radius of the clevis pin to be used. The arc wraps about half the periphery of the pin. A somewhat larger hole has a wall that intersects the wall of the arc such that the desired wrap of the arc is realized. The larger hole readily accepts the clevis pin, and lifting with the pin brings the pin into engagement with the arc wall. That arrangement can provide the largest load bearing contact with the pin that is achievable.
An arrangement somewhat less perfect in wrapping half the pin periphery, but still wrapping about eighty percent of half the pin periphery is accomplished with an egg shaped hole having the small end of the hole represent the radius of the pin. The egg shaped hole still engages the most effective area of the pin because the outer edges of an arc fitting the pin is nearly parallel to the lifting vector imposed on the pin and hole combination. The deformed area of a yielded surface on a pad eye is rarely as much as three fourths of the engageable half of the pin used. The egg shaped hole provides easy entry of the pin when installing the clevis. The egg shaped hole is an optional feature.
It is therefore an object of this invention to provide a pad eye with a hole that readily accepts the clevis pin but engages most of the pin compression, or lifting, surface when load is applied.
These and other objects, advantages, and features of this invention will be apparent to those skilled in the art from a consideration of this specification, including the attached claims and appended drawings.
REFERENCES:
patent: 3751932 (1973-08-01), Mathews, Jr.
patent: 4710061 (1987-12-01), Blair et al.
patent: 4919210 (1990-04-01), Schaefer, Jr.
patent: 5148871 (1992-09-01), Gullion
patent: 5392861 (1995-02-01), Champagne
patent: 5706863 (1998-01-01), Matherne et al.
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