GB2201517A

GB2201517A - Shackle testing

Info

Publication number: GB2201517A
Application number: GB08701917A
Authority: GB
Inventors: Arthur Graham Abraham
Original assignee: PROOF LOAD
Current assignee: PROOF LOAD
Priority date: 1987-01-28
Filing date: 1987-01-28
Publication date: 1988-09-01
Also published as: GB8701917D0; AU1227088A; WO1988005907A1

Abstract

To test the tensile strength of an apertured linking element such as a shackle (10) comprising a U-shaped member (12) having a removable pin (14) extending between the free ends (16) of the arms (18) thereof, extendable means are located between the arms (18) of the U-shaped member in engagement with the pin (14) and base (20) of the U-shaped member. The extendable means are then extended to push the pin and the base of the U-shaped member apart relative to one another. The extendable means may comprise two beams (24, 42) arranged in contact with the pin (14) and base (20) respectively and hydraulically operable piston and cylinder arrangements (34) disposed between the beams for pushing the beams apart relative to one another.

Description

SHACKLE TESTING This invention relates to testing the tensile strength of shackles which comprise a U-shaped member having a removable pin extending between the free ends of the arms thereof.

Conventionally such shackles are tested using tensile testing machines which pull the pin and base of the U-shaped member apart relative to one another to apply a tensile load thereto. With shackles rated for relatively large loads, for example loads in excess of 150 tonnes extremely large capacity tensile testing machines are required.

Typically, shackles are designed with a factor of safety of about eight and are required to be tested at loads which are about 50% in excess of their rating.

Thus, only in exceptional circumstances is the shackle likely to fail under tensile testing. With this realisation, the present invention is directed to enabling tensile testing of shackles to be carried out without using conventional tensile testing machines.

The invention includes a method of testing the tensile strength of a shackle comprising a U-shaped member having a removable pin extending between the free ends of the arms thereof, which method comprises pushing the pin and the base of the U-shaped member apart relative to one another to apply a tensile load to the shackle. The method may include locating extendable means between the arms of the U-shaped member in engagement with the pin and base of the Ushaped member, and extending the extendable means to push the pin and base of the U-shaped member apart relative to one another.

A protective enclosure may be provided about the shackle during the testing thereof in case the shackle fails under test.

The invention also includes a test rig for testing the tensile strength of as hackle comprising a U-shaped member having a removable pin extending between the free ends of the arms thereof, said rig comprising the shackle, extendable means located between the arms of the U-shaped member in engagement with the pin and base of the U-shaped member such that on extension of the extendable means the pin and the base of the U-shaped member are pushed apart relative to one another to apply a tensile load to the shackle, and means for providing a measure of, or limiting, the tensile load so applied.

The extendable means may comprise respective beams arranged in contact with the pin and base of the U-shaped member and extending from the shackle on each side thereof, and respective hydraulically operable piston and cylinder arrangements on each side of the shackle between the beams.

The piston and cylinder arrangements may be disposed in contact with the beams or alternatively the extendable means may further comprise packing disposed between the piston and cylinder arrangements and at least one of the beams.

The invention also includes apparatus for use in testing the tensile strength of a shackle comprising a U-shaped member having a removable pin extending between the free ends of the arms thereof, said apparatus comprising a first beam supported at opposed end portions by respective supports so as to extend substantially horizontally and to allow the pin or base of the U-shaped member of the shackle to extend beneath a central portion of the beam, means extendable upwardly of the beam mounted thereon, and a second beam adapted to be supported by said extendable means so as to extend beneath the base of the U-shaped member or the pin of the shackle such that in use of the apparatus when the two beams contact the pin and base of the U-shaped member respectively extension of the extendable means applies a tensile load to the shackle via said beams, and means for providing a measure of, or limiting, the tensile load so applied.

Preferably the beams are provided with curved sur face portions for contact with the pin and base of the U-shaped member respectively.

The extendable means may comprise respective hy 6 draulically operable piston and cylinder arrangements mounted on the end portions of the first beam and means for simultaneously operating said arrangements.

The second beam may comprise flat surface regions for contact with the piston and cylinder arrangements.

The apparatus may also comprise a set of packing pieces adapted to be inserted between the piston and cylinder arrangements and the second beam.

In order that the invention may be well understood and embodiment thereof, which is given by way of example only, will now be described with reference to the accompanying drawings, in which: Figure 1 is an elevation of a tensile test rig for, and including, a shackle; Figure 2 is a cross-section taken along the line A-A in Figure 1; Figure 3 is a fragmentary top plan view of the rig; Figure 4 is a hydraulic circuit diagram for the rigs; Figure 5 is a fragmentary end view of a modified tensile testing rig for, and including, a larger shackle than that included in the rig shown in Figures 1 to 3;and Figures 6 and 7 are respectively plan. and side views of a packing piece of the modified r?g.

Referring first to Figures 1 to 3, there is shown a test rig for testing the tensile strength of a shackle 10 which comprises a U-shaped member 12 having a removable pin 14 extending between the free ends 16 of the arms 18 thereof. The rig includes the shackle itself and the tensile testing of the shackle is carried out by pushing the pin 14 and the base 20 of the U-shaped member 12 apart relative to one another.

Broadly stated, this is achieved by locating extendable means indicated generally at 22, between the two arms 18 of the U-shaped member 12 in engagement with the pin 14 and base 20 and extending the extendable means to push the pin and base apart relative to one another to apply a tensile load to the shackle.

In more detail, in the embodiment, the rig includes apparatus which comprises a first beam 24 supported at opposed end portions 26 by respective support stands 28 so as to extend substantially horizontally and to allow the pin 14 to extend beneath a central portion of the beam when the shackle is dis posed with its pin downmost. Of course the shackle could be tested with its pin uppermost, in which case the base 20 of the U-shaped member would extend beneath the central portion of the beam 24.

As illustrated, the support stands are secured to the end faces of the beam 24 by threaded fasteners 30 and a tie bar 32 interconnects the support stands beneath the beam 24.

Respective thydraulically operable piston and cylinder arrangements 34 are mounted on the end portions 26 of the beam and include respective rams 36 which are extendable upwardly of the beam. As illustrated, each arrangement 34 is secured to a respective mounting base 38 by a threaded fastener, the mounting base beinglocated on a flat surface region 40 of the beam and secured to the beam by threaded fastening means.

A second beam 42 is supported by the piston and cylinder arrangements 34 such that the beams 24 and 42 contact the pin and the base of the U-shaped member respectively. The pin 14 and base 20 are circular in cross-section and the beams 24 and 42 are provided with curved surfaces 44 and 46 respectively for contact with the curved surfaces 48 and 50 of the pin 14 and base 20 respectively. As will be appreciated this arrangement produces a spot contact between the beam and shackle surfaces.

The end portions 52 of the beam 42 are provided with flat surface regions 54 for contact by the rams 36 of the piston and cylinder arrangements 34. In the illustrated embodiment the two beams 24 and 52 are of identical configuration with the flat surface regions 54 of the beam 52 corresponding to the flat surface regions 40 of the beam 24.

The apparatus includes means for simultaneously operating the piston and cylinder arrangements 34 and a hydraulic circuit diagram for the apparatus is shown in Figure 4. The hydraulic operating means comprises a unit 56 housing a hydraulic fluid reservoir 58, a pump 60 for pumping fluid from the reservoir to a twoposition control valve 62 from whence the flow is directed to two outlets 64 each of which is connected to a respective piston and cylinder arrangement 34 via an inlet 66 therefor. A pressure relief valve 68 is provided between the pump and valve.

A pressure gauge 70 measures the pressure of the fluid being delivered to the piston and cylinder arrangements and is calibrated to provide a reading of the tensile test load being applied by the piston and cylinder arrangements. Thus, by using the gauge, the rig can be operated to apply a predetermined tensile test load to the shackle. A possible alternative is to provide a pre-settable limiting arrangement which will limit the fluid pressure to that which will provide the test load. Furthermore, additionally or alternatively, load cell means, say a load cell associated 6 with each respective piston and cylinder arrangement, for example in the ram thereof, could be provided to enable the tensile load to be measured.

Referring now to Figure 5, there is shown a modified tensile testing rig using the apparatus heretofore described but including a larger shackle than that included in the rig shown in Figures 1 to 3. The rig parts in Figure 5 which correspond to the rig parts in Figures 1 to 3 have been given like reference numerals.

As will be noted, the distance between the pin 14 and base 20 of the shackle illustrated in Figure 5 is greater than that of the shackle illustrated in Figures 1 and 2. To cater for this increase, packing pieces are inserted between the piston and cylinder arrangements 34 and the flat surface regions 54 of the beam 42. As illustrated one packing piece 72, two packing pieces 74 and one packing piece 76 are being used. The packing pieces 72, 74 and 76 each have a different depth and accordingly can be used singly or in various combinations in order to cater for different distances between the pin 14 and base 20.

Figures 5 and 6 illustrate one packing piece in more detail. The packing piece is provided with a handle 78 at one end edge thereof and is curved at the opposite end edge 80 for abutment against a corresponding curved edge 82 (shown in dotted line in Figure 3) when the packing piece is disposed against one of the flat regions 54 of the beam 42.

Claims

CLAIMS:

1. A method of testing the tensile strength of a shackle comprising a U-shaped member having a removable pin extending between the free ends of the arms thereof, which method comprises pushing the pin and the base of the U-shaped member apart relative to one another to apply a tensile load to the shackle.

2. A method as claimed in claim 1, including locating extendable means between the arms of the U-shaped member in engagement with the pin and base-of the U-shaped member, and extending the extendable means to push the pin and base of the U-shaped member apart relative to one another.

3. A test rig for testing the tensile strength of a shackle comprising a U-shaped member having a removable pin extending between the free ends of the arms thereof, said rig comprising the shackle, extendable means located between the arms of the U-shaped member in engagement with the pin and base of the U-shaped member such that on extension of the extendable means the pin and the base of -the U-shaped member are pushed apart relative to one another to apply a tensile load to the shackle, and means for providing a measure of, or limiting, the tensile load so applied.

h. A test rig as claimed in claim 3, wherein the extendable means comprises respective beams arranged in contact with the pin and base of the U-shaped member 6 and extending from the shackle on each side thereof, and respective hydraulically operable piston and cylinder arrangements on each side of the shackle between the beams.

5. A test rig as claimed in claim 4, wherein the piston and cylinder arrangements are disposed in contact with the beams.

6. A test rig as claimed in claim 4, wherein the extendable means further comprises packing disposed between the piston and cylinder arrangements and at least one of the beams.

7. Apparatus for use in testing the tensile strength of a shackle comprising a U-shaped member having a removable pin extending between the free ends of the arms thereof, said apparatus comprising a first beam supported at opposed end portions by respective supports so as to extend substantially horizontally and to allow the pin or base of the U-shaped member of the shackle to extend beneath a central portion of the beam, means extendable upwardly of the beam mounted thereon, and a second beam adapted to be supported by said extendable means so as to extend beneath the base of the U-shaped member or the pin of the shackle such that in use of the apparatus when the two beams contact the pin and base of the U-shaped member respectively 6 extension of the extendable means applies a tensile load to the shackle via said beams, and means for providing a measure of, or limiting, the tensile load so applied.

8. Apparatus as claimed in claim 7, wherein the beams are provided with curved surface portions for contact with the pin and base of the U-shaped member respectively.

9. Apparatus as claimed in claim 7 or 8, wherein said extendable means comprises respective hydraulically operable piston and cylinder arrangements mounted on the end portions of the first beam and means for simultaneously operating said arrangements.

10. Apparatus as claimed in claim 9, wherein said second beam comprises flat surface regions for contact by said piston and cylinder arrangements.

11. Apparatus as claimed in claim 8 or 9, comprising a set of packing pieces adapted to be inserted between the piston and cylinder arrangements and said second beam.

12. A method of testing the tensile strength of a shackle, which method is substantially as herein described with reference to the accompanying drawings.

13. A test rig for testing the tensile strength of a shackle, said test rig being substantially as herein described with reference to the accompanying drawings.

14. Apparatus for use in testing the tensile strength of a shackle, said apparatus being substantially as herein described with reference to the accompanying drawings.