GB2465578A

GB2465578A - Load test apparatus

Info

Publication number: GB2465578A
Application number: GB0821265A
Authority: GB
Inventors: Alan Milne; Keith Denby; John A Parr; David J Letts; Simon Greaves; David Massingham; John Roberts
Original assignee: WATER WEIGHTS Ltd
Current assignee: WATER WEIGHTS Ltd
Priority date: 2008-11-20
Filing date: 2008-11-20
Publication date: 2010-05-26
Also published as: GB0821265D0

Abstract

Apparatus for load testing comprises a liquid impervious collapsible bag 10 with an inlet valve 23 for filling the bag with water. Reinforcing straps 15 strengthen the bag and enable it to be hoisted onto a load bearing structure to be tested. The bag 10 is designed to be able to stand up on its own when fully laden; it will not fall over when filled with water. This helps it to be set down as part of a load testing procedure.

Description

Load test apparatus This invention relates to load test apparatus, in particular, though not exclusively, for testing the lifting strength of cranes, hoists, winches and other load bearing structures.

The invention provides load test apparatus comprising a liquid impervious collapsible bag, a plurality of reinforcing straps, and means for allowing liquid into and out of the bag, wherein the apparatus is designed to be capable of being used in two conditions whilst the bag is fully laden with liquid, in a first condition the apparatus being suspended from a structure by its straps and in a second condition the apparatus being set down on a supporting surface, the configuration of the bag and strap arrangement ensuring that the apparatus is capable of standing freely by itself in said second condition without toppling over.

By way of example, embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figures 1 and 2 are front elevational and underneath plan views showing a form of load test apparatus according to the invention, and Firgures 3 and 4 are front and back elevational views of the apparatus of Figures 1 and 2, with its bottom reinforcing shroud in position.

The load test apparatus seen in the drawings is in the nature of a collapsible container for carrying a measured amount of liquid, typically water. In its filled state, the apparatus and its liquid contents can be used to load test structures such as cranes, hoists, winches and the like. After testing, the apparatus can be emptied of its contents and folded up for ease of transportation and storage.

Load test apparatus of this general nature have been used successfully for many years. A novel feature of the apparatus seen in the drawings is that it is designed to be additionally capable of standing up by itself whilst carrying its liquid load, without toppling over. This allows the apparatus to be set down on the ground and left unsupported. This is particularly advantageous, because it is often desirable in practice to be able to release a test load from a structure during load testing procedures.

As will be seen in Figures 1 and 2, the apparatus comprises a flexible bag 10 having a generally circular shaped base portion 11, with a generally cylindrical shaped sidewall portion 12 extending upwardly therefrom. The height of the sidewall portion 12 is approximately V2 the diameter of the base portion 11. A generally conical shaped cover portion 13 extends upwardly from the sidewall portion 12 and terminates in a flat lid portion 14. The overall height of the bag 10 from the base portion 11 to the lid portion 14 is approximately 2/3 the diameter of the base portion. The bag thus has a squat overall appearance.

The bag 10 is made of suitable material such as heavy duty PVC sheeting, with stitched and welded seams. The bag 10 is strengthened by an arrangement of reinforcing straps 15. In this case, there are sixteen such straps, equally spaced around the bag 10. As seen in Figure 2, the straps 15 are all connected together at one of their free ends by means of a harness assembly 16 situated on the underside of the base portion 11. From the harness assembly 16, the straps 15 extend radially outwardly through a series of bottom guide sleeves 17 attached to the underside of the base portion 11, through a series of lateral guide sleeves 18 attached to the sidewall portion 12 and finally through a set of upper guide sleeves 19 attached to the cover portion 13. The straps 15 then extend beyond the cover portion 13 where they are gathered together at their other free ends in the form of a sling assembly (see Figure 4). The sling assembly 20 forms a hoisting point by which the apparatus can be shackled to a structure to be load tested.

The harness assembly 16 is in the form of an endless ring 26 to which each of the straps 15 is attached. The ring 26 is located within a circular collar 27 that is attached to the underside of the bag 10. The ends of the straps 15 are arranged to extend through slots in the collar 27 and are looped around the ring 26. The harness assembly 16 is thus effectively located in position relative to the bag 10 without being cormected directly to it.

The arrangement of the straps 15 is vital to the integrity of the apparatus structure. Load test apparatus are usually required to be able to withstand several times their own static weight, typically using a safety factor of six. This is usually pre-tested by effecting a controlled drop of the apparatus through a predetermined distance whilst it is fully laden arid in suspension from a structure. The straps 15 are thus designed firstly to be strong enough to withstand loads of this magnitude.

Additionally, however, the arrangement of the straps ISis also designed to cope with the changes in shape that the apparatus will inevitably experience during the various stages of its use. During initial filling of the bag 10, for example, which is normally done whilst the apparatus is being suspended, the bag tends to hang down in an elongate configuration. The bag fills out as it is filled with liquid so that its profile becomes more rounded and pear-shaped. When the apparatus is set down, however, the bag 10 assumes a much squatter profile, more like the shape shown in Figure 1. By using a series of guide sleeves to locate the straps relative to the bag, this allows the possibility for a degree of relative movement between the straps and bag. The guide sleeves also help to achieve an even spread between the straps during the filling process and prevent them from bunching, which can lead to excessive bulging of the bag at certain points.

When the apparatus is set down so as to be fully supported by the ground or a supporting surface, the straps 15 are all under tension. This arrangement helps to take the load on the sidewall portion 12 of the bag 10, whilst also contributing to the lateral stability of the apparatus in this condition. The length of the straps 15 is a key factor in this.

Whenever the apparatus is to be set down or picked up off the ground or a supporting surface, it can be expected to experience some sideways movement. To guard against the possibility of this causing damage to the bag 10 by repeated scuffing, the apparatus further comprises a bottom reinforcing shroud 21, as seen in Figures 3 and 4. The shroud 21 is made of a suitably tough material such as 4-ply tarpaulin. As seen in Figures 3 and 4, the shroud 21 is arranged to extend over the base portion 11 of the bag 10 and part way up the sidewall portion 12. The shroud 21 is designed to be detachable from the bag 10 so that it can be replaced when it gets worn. The shroud 21 is attachable to the bag 10 by means of a plurality of straps and buckles 22 arranged around the sidewall portion 12.

The bag 10 is filled with liquid (usually water) via an inlet valve 23 (in this case in the form of a manhole cover assembly) in the lid portion 14.

Filling takes place whilst the apparatus is suspended from the structure to be tested. Once filling is complete, the inlet valve 23 is closed and the apparatus is ready for use.

The bag 10 is designed to hold a certain predetermined volume of liquid, ie to be of a known weight when full. This will conveniently be a standard amount for proof load testing purposes. For example, a bag laden with 12.5 m3 of water and weighing 12.5 tons would be suitable for proof testing a nominal 10 ton crane.

The bag 10 is provided with an outlet valve 24 for emptying its liquid load. The outlet valve 24 is located in the sidewall portion 12, a small distance above the base portion 11. Emptying takes place whilst the apparatus is still being suspended and in two phases. In the first phase, the main bulk of liquid is allowed to drain from the bag 10, ie down to the level of the outlet valve 24. In the second phase, the remainder of the liquid is emptied from the bag 10 and for this, the bag is provided with a secondary sling assembly 25 (see Figure 4). The secondary sling assembly 25 is located on the sidewall portion 12 of the bag 10, at a similar level to the outlet valve 24, but diametrically opposite to it. To empty the remaining liquid in the bag 10 after the first emptying phase, the apparatus is set down, unshackled from the main sling assembly 20 and then re-shackled to the secondary sling assembly 25.

Because of the offset of the secondary sling assembly 25, hoisting the apparatus from this point causes the bag 10 to tilt, thus tipping the remaining liquid out of the outlet valve 24.

Claims

CLAIMS1. Load test apparatus comprising a liquid impervious collapsible bag, a plurality of reinforcing straps, and means for allowing liquid into and out of the bag, wherein the apparatus is designed to be capable of being used in two conditions whilst the bag is fully laden with liquid, in a first condition the apparatus being suspended from a structure by its straps and in a second condition the apparatus being set down on a supporting surface, the configuration of the bag and strap arrangement ensuring that the apparatus is capable of standing freely by itself in said second condition without toppling over.
2. Apparatus as claimed in claim 1 wherein the straps are connected together at a first common point beneath the bag.
3. Apparatus as claimed in claim 2 wherein said first common connection point comprises a harness assembly.
4. Apparatus as claimed in claim 3 wherein the apparatus comprises means for locating said harness assembly in position relative to the bag.
5. Apparatus as claimed in claim 1, claim 2 or claim 3 wherein the straps extend from said first common connection point beneath the bag to a second common connection point above the bag.
6. Apparatus as claimed in claim 5 wherein said second common connection point comprises a sling assembly.
7. Apparatus as claimed in any preceding claim wherein the straps are located relative to the bag by means of guide sleeves aftached to the bag, the guide sleeves allowing for a degree of relative movement between the straps and the bag in use of the apparatus.
8. Apparatus as claimed in any preceding claim wherein the means for allowing water into and out of the bag comprises separate filling and drain valves.
9. Apparatus as claimed in claim 8 wherein the filling valve is located at a higher position on the bag than the drain valve.
10. Apparatus as claimed in claim 8 or claim 9 wherein the drain valve is located at a position spaced higher than the bottom of the bag.
11. Apparatus as claimed in claim 10 wherein the apparatus comprises an alternative hoisting point for suspending the apparatus to assist with the process of emptying liquid from the bag.
12. Apparatus as claimed in any preceding claim wherein the apparatus comprises means for protecting the bottom of the bag against damage.
13. Apparatus as claimed in claim 12 wherein said means for protecting the bottom of the bag is removably attachable to the bag.
14. Apparatus as claimed in claim 12 or claim 13 wherein said means for protecting the bottom of the bag comprises a shroud which is attachable to the bag by means of straps and buckles.
15. Apparatus substantially as herein described with reference to the accompanying drawings