GB2210845A

GB2210845A - Improvements in load handling

Info

Publication number: GB2210845A
Application number: GB8723899A
Authority: GB
Inventors: Ketel Hendrik Van
Original assignee: HEEREMA ENGINEERING
Current assignee: HEEREMA ENGINEERING
Priority date: 1987-10-12
Filing date: 1987-10-12
Publication date: 1989-06-21
Also published as: GB8723899D0; NO884529D0; NO884529L; BR8805305A; EP0312337A1

Description

n n L 1- 1 lit b 4S IMPROVEMENTS IN LOAD HANDLING This invention relates

to load handling apparatus.

The invention provides load handling apparatus comprising at least one hoisting device having a lifting cable system, sling means having means for connection to a load, and means connecting the sling means to the lifting cable system, the sling means being adjustable in length whilst connected between the lifting cable system and the load.

The invention also provides a method of handling a load using load handling apparatus as defined above.

By way of example, embodiments of the invention will now be described with reference to the accompanying drawings, in which.

Figure 1 illustrates load handling apparatus according to the invention, Figures 1A to 1L show examples of various alternative arrangements, Figures 2 and 3 illustrate an alternative form of load handling apparatus, Figures 4 and 5 illustrate another alternative form of load handling apparatus, Figure 6 illustrates a further alternative form of load handling apparatus, Figures 7 and 8 illustrate other arrangements of load handling apparatus, and Figure 9 illustrates use of the load handling apparatus in an installation procedure.

There is seen in Figure 1 a standard hoisting device having bottom tackle of a hook 10 and lower pulley block-11, upper pulley block 12, cable system is 13 and winch assembly 14. Ll indicates the hoist range, ie the possible travel of the bottom tackle in this hoisting device. The hoist range of a hoisting device is limited by the maximum obtainable single length of cable. At present, the capacity of cable manufacturers is limited to the production of a single length of wire rope of no more than about 180 tons in weight'. In general, hoisting devices for handling heavier loads require larger diameter cables. Therefore, hoisting devices which are designed for handling the heaviest loads will have correspondingly short hoist ranges. To offset this disadvantage, the load handling apparatus of the present invention is proposed, and an example is seen in Figure 1. Here, the load handling apparatus simply takes the form of a hoisting device having a lifting cable system, and an additional block and tackle assembly 15 connected between the bottom tackle of the hoisting device and the slings 16 by which the load 17 is suspended. The block and tackle assembly 15 here has its own winch assembly 18, and is operable over a hoist range L-2. It will be seen 3 that the arrangement enables the effective overall hoist range of the hoisting device to be increased.

The winch assembly 18 may be provided as an integral part of the additional block and tackle assembly 15 or located elsewhere, eg on the hoisting device itself or on a deck. The winch assembly 18 can be provided with simple means of paying in and winding up the unloaded cable, combined with a locking device to hold the full cable tension under load. Alternatively, the winch assembly 18 can itself act as an active hoist system which is is operable independently of the hoisting device. The additional block and tackle asembly 15 may comprise a cable system having a single winch and a dead end.

Alternatively, there may be a double drum winch assembly for the cable system, with both drums mechanically or electrically synchronised. It will be appreciated that the additional block and tackle assembly (or equivalent device) could be connected to the lifting cable system by means other than the hook of the bottom tackle shown in Figure 1. For example, the bottom tackle need not have a hook. Or the bottom tackle may form part of the additional block and tackle assembly (or equivalent device) itself.

Examples of the various different arrangements are illustrated in Figures 1A to 1L. The original hoist range of a crane is shown by arrow a in Figure 1A. An additional block and tackle assembly 15 with its own storage drum 18 is connected between the crane cable system and the load 17 (Figure 1B) and extended to the required length and locked (Figure 1C). Now (Figure 1D) the load 17 can be lowered by 4 an additional amount, arrow b, compared with the original hoist range, arrow a. This is a passive sys Cem. The winch assembly 18 of the additional block and tackle assembly may alternatively be located on the crane itself (Figure lE) or on deck (Figures 1F and 1G),. possibly using an additional hanger block on the crane (Figure 1F) If the winch assembly 18 is itself suspended from the crane cable system, it may be located in or nearby the upper or lower pulley blocks of the additional assembly 15 (Figure lH). Figures 1J, 1K and 1L show use of the arrangement illustrated in Figure 1F as an active is system. The load 17 is suspended by slings from the additional block and tackle assembly 15 which is connected to the crane cable system (Figure 1J). The load 17 is lowered by an amount Ll using the winch assembly 18 of the additional assembly 15 (Figure 1K). The load 17 is lowered further using the crane hoist which is lowerable through its range h (Figure 1L), after which the' additional device has a length L2. Length L2 is less than Ll by an amount which depends upon the number of falls in the additional block and tackle assembly 15, and is given by the formula L2 = Ll - h/n where n is the number of falls.

An alternative form of load handling apparatus is seen in Figure 2. It is conventional in offshore heavy lifts to use slings of wire rope to handle loads. The diameter of such slings as are used nowadays has already reached a size of 14 inches.

Although the slings used are nominally of the same fixed length, differences occur in practice due to tolerances, uneven elongation etc. Compensation can be made for this to some degree by appropriate design of the lower pulley block and hook assembly.

Nevertheless, the detrimental effects of extreme differences in sling length cannot be eliminated.

To offset this problem, the load handling apparatus of the present invention is proposed and an example is shown in Figure 2.' Here, the load handling apparatus includes a replacement for the conventional slings by which the load 17 is normally hung from the bottom tackle 10 of the hoisting device. The replacement for the slings comprises additional block and tackle assemblies 20 and 21, each having its own winching sys tem.' Figure 3 shows how the arrangement is provides the possibility of manipulating the load 17 using the winching systems of the additional block and tackle assemblies 20 and 21.

An alternative arrangement is seen in Figure 4. Here, load 17 is supported partly by conventional means 25 and partly via a device replacing conventional slings. The sling replacement here comprises two additional block and tackle assemblies 26 and 27, each of whi-ch shares the same single cable system, under control of a single winch assembly 29.

28 indicates the cross-over of the cable between the two assemblies 26 and 27, and alternative cross-overs are shown in dotted lines. Figure 5 shows how the arrangement of the assemblies here gives a self-aligning system, so that guidance or a second hoist arrangement is needed because the rigging is unstable. Also seen in Figure 5 is that the upper pulley blocks of the two additional block and tackle assemblies 26 and 27 have been integrated into a single assembly.

6 In Figure 6 a alternative form of load handling apparatus is seen. Here, the possibiliy is illustrated of combining several additional block and tackle assemblies 30, 31 by connecting the dead ends 32, 33 to each other via an equaliser 34.

In Figures 7 and 8, alternative equaliser arrangements are seen. In Figures 7, the two additional block and tackle assemblies 40, 41 have their dead ends 42, 43 connected by an equaliser beam 44 which is pivotable on fulcrum 45. In Figure 8, the two additional block and tackle assemblies 50, 51 is have double drum winch arrangements and their cable systems 52, 53 are linked together via an equaliser cable system 54.

Figure 9 illustrates use of a load handling apparatus in a practical situation. In a conventional four point lift using two vessels and four hoisting devices the problem which typically arises is a slacking off of one set of slings 60 as a result of relative motion between the vessels or unsynchronised hoisting action between the four hoisting devices. As shown in Figure 9, two of the sets of slings 60 of a conventional arrangement have been replaced by a device 61 which is connected to the lifting cable systems of the two hoisting devices on one of the vessels. Now, as will be seen, the load handling apparatus is able automatically to compensate for relative vessel motions and maintain an even distribution of load between the hoisting devices.

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Claims

CLAIMS:

Load handling apparatus comprising at least one hoisting device having a lifting cable system, sling means having means for connection to a load,, and means connecting the sling means to the lifting cable system, the sling means being adjustable in length whilst connected between the lifting cable system and the load.
2. Apparatus as claimed in Claim 1 wherein the sling means comprises at least one block and tackle assembly.
3. Apparatus as claimed in Claim 1 or Claim 2 wherein the sling means comprises at least two block and tackle assemblies connected between the lifting cable system and respective points on the load, which assemblies share a common cable system.
4. Apparatus as claimed in Claim 1 or Claim 2 wherein the sling means comprises at least two block and tackle assemblies connected between the lifting cable system and respective points on the load, which assemblies each have their own cable system.
5. Apparatus as claimed in Claim 4 wherein equaliser means is provided linking together the cable systems of the two or more block and tackle assemblies.
6. Apparatus as claimed in any preceding claim and including means for adjusting the length of the sling means whilst the sling means is under load.

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7. Apparatus as claimed in claim 6 wherein said means for adjusting the length of the sling means comprises-at least one winch assembly.
8. Apparatus as claimed in Claim 7 wherein said at least one winch assembly is located remote from the lif ting cable system and the load, eg on a deck, and is operable independently of the hoisting device itself.
9. Apparatus as claimed in any preceding claim in which there are at least two independent hoisting devices and a block and tackle assembly which is connectable to the lifting cable systems of the hoisting devices.
10. Apparatus as claimed in any preceding claim in which there are at least two independent hoisting devices and at least two block and tackle assemblies which are connectable to the lifting cable systems of the hoisting devices.
11. Apparatus substantially as hereinbefore described with reference to the accompanying drawings.
12. A method of handling a load using load handling apparatus as claimed in any preceding claim.

Published 1988 at The atent office. state House. 66.71 High Holborn, London WC1R 4TP. Further copies mkv be obtained from The Patent Office, Sales Branch, St Mary Cray, OlPingtor., Kent BP-. 31RD- Printed by Multiplex techniques ltd. St Mary Cray. Kent Con. V87-