Patent Number: 042742056
Section: description

DESCRIPTION A measuring fixture 11 according to the invention is illustrated in FIG. 1 as mounted in operating position along a wall 12 in a pool by water 13. The main frame of the fixture is an elongated support beam 14 shown herein as an H beam. An upper bracket 16, attached to the beam 14 near its upper end, includes a pair of rearwardly extending arms 17 formed to hook over a ledge 18 of the pool wall 12 to thereby support the fixture 11 in suspension along the wall 12. Adjustable pads 15 provide verticality adjustment. A lower bracket 19, attached to the beam 14 at its lower end, includes a pair of side plates 21. Rearward extensions 22 abut the wall 12 to position the beam 14 substantially parallel with the wall 12. Forward extensions 23 and a cross plate 24 provide support for other components of the fixture as described hereinafter. Supported between lower bracket 19 and an intermediate bracket 26 is a straight edge member 27 which serves as an accurate measurement plane of reference and as a track for an instrument bearing carriage 28. As best shown in FIG. 2, straight edge 27 is supported at its lower end by lower bracket 21 with a pair of pivot pins 29, and it is held in position at its upper end by intermediate bracket 26 with a center pin 31 carrying a sliding, spherical bearing journalled in a flange 32 of bracket 26. This mounting arrangement allows the straight edge 27 freedom of thermal expansion and contraction and aids in preventing transmission thereto of deforming loads from other portions of the fixture. To further minimize thermal deformation, the straight edge 27 is formed with a series of relatively large, equally spaced holes 33 along its length. To minimize torsional distortion of the support beam 14 that would affect the straight edge 27, the portion of beam 14 between intermediate bracket 26 and the lower end of the beam is "boxed in" by a back plate 34 secured, as by welding, to the rear edges thereof. The part of the beam 14 above the intermediate bracket 26 is left unboxed. Thus any twisting of beam 14, as might occur for example from unevenness of the pool wall 12, takes place in the part of the beam above the intermediate bracket 26 whereby transmission of such deformation to the straight edge 27 is avoided. The component to be measured, shown in FIG. 1 in phantom view by dashed lines as a fuel assembly flow channel 36 is removably secured in a position generally parallel to the straight edge 27. The channel 36 is supported at its bottom end by a channel support member 37 and is positioned at its top end by a clamp arrangement 38 secured to the top end of straight edge 27. The clamp arrangement 38 includes a fixed arm 39 and a swinging arm 41, the swinging arm 41 being remotely operable by a hydraulic or pneumatic cylinder 40 in well-known manner. The fixed arm 39 is fitted with a pair of jack screws 42 for adjustment of the alignment of the top end of the channel with the plane of the tips of the measuring devices on carriage 28. The channel contacting faces of the swinging arm 41 and the jack screws may be fitted with material such as nylon to prevent scratching of the channel. The channel is supported at its bottom end by channel support member 37, in a manner which does not restrain the channel from rotational motion about is longitudinal axis. This is necessary for measurement of channel twist. As shown in FIG. 3, this feature is provided by a support socket 43 which is journalled to allow rotational motion thereof by an annular ball bearing 44 carried by a bearing plate 46 secured to a spacing sleeve 47 which, in turn, is secured to the cross plate 24 of the lower bracket 19. The subject measuring fixture is adapted to accommodate and measure empty channels or flow channels which are still mounted on fuel assemblies (as shown in previously mentioned U.S. Pat. No. 3,689,358). Therefore, the upper end of the bore of support socket 43 is appropriately shaped, as at 48, to receive and mate with the nose pieces of the fuel assemblies to be accommodated. To accommodate empty flow channels, an empty channel adapter 49 is provided. The lower end 51 of the channel adapter has the shape of a fuel assembly nose piece for fitting into the support socket 43. The upper end 52 of the channel adapter has a pyramid shape, or the like, for ease of fitting the square end of the empty channel thereover and the adapter is sized at 53 near the base of the pyramid portion to fix the position of the channel 36 on the channel adapter. It is noted that, as shown in FIG. 3, the cross plate 24 and the bearing plate 46 are formed with large holes 45 and 50, respectively, and the support socket 43 and the adapter 49 are formed with large through bores. This provides for water circulation through the component being measured which allows water that has become radioactive in the component to drain away thus reducing user exposure. It also provides a convection path to convey heat away from the measuring devices. Empty channels or fuel assemblies, as the case may be, can be placed in position or removed from the measuring fixture by any suitable lifting and maneuvering device such as an overhead or boom mounted hoist (not shown) which is typically available as an adjunct to a nuclear fuel storage pool. Such hoist arrangements are shown, for example, in copending patent application Ser. No. 747,824 filed Dec. 6, 1976, now U.S. Pat. No. 4,172,760. Attention is now directed to the instrument carriage 28 shown in FIG. 1 and with greater clarity in FIG. 4. As illustrated herein the carriage 28 which is mounted on the straight edge 27 by a system of rollers or wheels includes a T-shaped front plate 54 which serves as the main frame of the carriage. The front plate 54 is positioned with respect to and guided along the straight edge 27 by a plurality of guide rollers. These guide rollers include a first pair of spaced rollers 56(1) and 56(2) journalled to the T portion of plate 54 for engagement with the right-front face portion of straight edge 27, a second pair of spaced rollers 57 likewise journalled to the T portion of plate 54 but for engagement with the right side of straight edge 27, and a single roller 58 journalled near the left hand end of plate 54 for engagement with the left-front face portion of straight edge 27. A plurality of rollers 59 journalled in a stud-mounted, spring-loaded back plate 61 and a pair of rollers 62 journalled in a stud-mounted, spring-loaded side plate 63 provide pressure on the guide rollers and assure their engagement with straight edge 27. Secured to the right hand end of plate 54 is an arm 64 suitable for supporting a plurality of distance detectors or other measuring devices 66(1)-66(3) in appropriate position for engagement with the flow channel 36 to be measured. The devices 66(1)-66(3) may be, for example, linear variable differential transformers. Briefly, such a device comprises a linearly movable spring loaded plunger 67 extending from a housing. Movement of the plunger 67 changes the mutual inductance of a pair of coils within the housing. Thus the mutual inductance of the pair of coils can be measured and interpreted as a function of the linear position of the plunger. The plunger 67 is fitted at its outer end with a rounded, smooth-faced nose piece 69 for sliding engagement with the outer surface of the channel 36 to be measured. Suitable such distance detectors are available from Schaevitz Engineering, U.S. Route 130 and Union Avenue, Pennsauken, New Jersey as catalog item No. GCA-121-500-0624. The signals from detectors 66(1)-66(3) are transmitted via a cable 71 to a signal processing recording and display device 72 (FIG. 1). A suitable device 72 is available from Schaevitz Engineering as catalog item No. CAS-0653. To be noted is that the detectors 66(1)-66(3) are supported such that the direction of measurement is in the direction of the major cross section dimension of straight edge 27 and hence in the direction of maximum straight edge stiffness. As illustrated herein, the carriage 28 is manually movable along the length of straight edge 27 as follows: A roller chain 73 attached to the carriage 28 is engaged by a lower idler sprocket wheel 74 and by an upper driven sprocket wheel 76. Wheel 76 is driven from a hand wheel 77 through suitable shafting and a pair of right-angle gear boxes 78(1) and 78(2). A counter 79 registers the rotations of the hand wheel 76 and can be designed to indicate the position of the carriage 28 along the straight edge 27 in convenient units. Also, a toothed wheel 82 engaged by a spring-loaded ball detent can be keyed to the shaft of hand wheel 77 to provide incremental carriage positioning and prevent carriage drift. It is noted that the chain 73 is attached to the carriage 28 as nearly as feasible to the center of gravity thereof to minimize twisting forces on the carriage due to the lifting force. Also, a counterweight 80 may be fitted to chain 73 to balance the weight of the carriage 28. To provide reference readings to the processing device and to check linearity of the detectors, a calibration block 81 is secured to the bearing plate 46 of support member 37 as shown in FIG. 3. The block 81 is stepped to provide three reference planes for engagement with the distance detectors 66(1)-66(3). The center step can be, for example, a zero reference plane, the lower step a positive reference plane and the upper step a negative reference plane. Operation of the measuring fixture is as follows: A flow channel to be measured is placed on the support socket 43 and clamped in position by clamp arrangement 38 as previously described. Operation of handwheel 77 moves the carriage 28 along straight edge 27 and the detectors 66(1)-66(3) provide signals indicative of the profile of the center and outer tracks of their engagement with the adjacent side of the channel. From these profile traces, flatness, bow and twist of that side of the channel can be determined. The other sides of the channel similarly can be measured by release of clamp 38, rotation of the channel by ninety degrees and reengagement of the clamp. In an embodiment of the measuring fixture the straight edge 27 is about 2 inches (5.1 cm) thick, 8" (20.3 cm) wide and 14 feet (43 m) long. It is formed of carbon steel for machineability, accurately ground and electroless nickel plated for corrosion resistance. The holes 33 are about 5.5 inches (14 cm) diameter spaced about 7.5 (19.1 cm) center-to-center. The support beam 14 is an 8 inch (20.3 cm) H beam. This and other structural members of the fixture are preferably formed of aluminum to minimize the weight of the fixture for ease of portability.