Patent Number: 05999584&
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description, like reference characters designate like or corresponding parts throughout the several views. Also in the following description, it is to be understood that such terms as "forward", "rearward", "left", "right", "upwardly", "downwardly", and the like are words of convenience and are not to be construed as limiting terms. Referring now to the drawings in general and FIG. 1 in particular, it will be understood that the illustrations are for the purpose of describing a preferred embodiment of the invention and are not intended to limit the invention thereto. As best seen in FIG. 1, there is illustrated a prior art system for lifting a reactor pressure vessel head. The lifting operation is conducted using a cable (not shown) connected to lifting eye 300 of tripod handling fixture 100 ("tripod"). Each leg of tripod 100 carries a rigging component used to lift reactor pressure vessel head 105. In the prior art system, turnbuckle pendants 102 extend downwardly from each tripod mounting point. A clevis 104 is provided at the lower end of each turnbuckle pendant 102 for attaching additional components. Typically, a solid rod lifting pendant 113 as shown in the exploded view of FIG. 2 is connected between the lower end of turnbuckle pendant 102 and pressure vessel head lifting eye 107. Alternatively, a bridge strand pendant (not shown) may be used in place of the turnbuckle pendant. In this example, three of each of the items discussed above are provided at equidistant points around the circumference of reactor closure head 105. Secured to the top of head 105 is a service structure 117. Atop the service structure is positioned a work platform 116 which serves as a staging area for personnel and equipment. Solid rod lifting pendants 113 extend through openings 118 and work platform 116 to make up the necessary connections. Alternatively, bridge strands (not shown) may be substituted for the solid rod lifting pendants 113. The prior art rigging system described above requires four rigging changes during an outage because the components that are suitable for mating up to the pressure vessel head 105 are not suitable for mating up to the reactor internals. Although the type of connections that must be made up are relatively simple, the large weight of the components makes their handling difficult, time consuming, and necessitates prolonged exposure to high radiation components. For example, the turnbuckle pendants 102 and the bridge strands each weigh several hundred pounds each. The connecting pins 107 for these components may weigh one hundred pounds or more and must be positioned and driven into place by hand. The workers carrying out these tasks must often work at awkward angles thus increasing the possibility of personal injury as the number of required rigging changes increases. A rigging system constructed according to the present invention is illustrated in FIGS. 3 and 4. Tripod 100 carries three latchbox pendants 211 each of which include a leveling turnbuckle 212 and a latchbox 219. The construction and operation of latchbox 219 is well known in the art and will not be described in detail here. According to the present invention, each of the latchbox pendants 211 is secured to a novel solid rod lifting pendant 213. As shown in FIG. 4, each solid rod lifting pendant 213 includes a T-shaped lifting lug 250 at a first end, a clevis 215 at the opposite end and an adjustable turnbuckle 216 adjacent to the T-shaped lifting lug 250 which allows the reactor head 105 or other item being lifted to be leveled without changing the reactor internals lift settings on the latchbox pendants 211 after they have been initially set. In operation, as the tripod 100 and the downwardly extending latchbox pendants 211 are lowered through access openings 118 in the work platform 116, each lifting lug 250 engages a corresponding latchbox 219 without the need for manhandling a connector or cable. Although a T-shaped lug 250 is illustrated in FIG. 4, other lugs types will work as well, depending on the internal design of the particular latchbox 219. The advantages of the present invention stems from the fact that the latchbox pendants 211 may be rigged once to tripod 100 and left in place throughout the entire rigging sequence. There is no need to rig latchbox pendants 211 to tripod 100 for reactor internals handling (see FIG. 5) and then change to turnbuckle pendants 102 for reactor closure head handling. For reactors that have solid lifting rods already installed in place of cables, the practice of the present invention requires only that adjustable turnbuckles 216 and lifting lugs 250 be installed thereon. Note that the present invention does not affect the interface between the shielded work platform (not shown) and the service structure work platform 116 and, therefore, does not require expensive modifications to the structure. Certain modifications and improvements will occur to those skilled in the art upon a reading of the foregoing description. By way of example, while the preferred embodiment of the invention teaches adding the lifting lug and turnbuckle to a solid lifting rod, the present invention can still be used on cable-type systems by manually inserting the lifting lug into the latch box pendant. It should be understood that all such modifications and improvements have been deleted herein for the sake of conciseness and readability but are properly within the scope of the following claims.