lec"s"coril The time has arrived once again for CM's review
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of the state of the load-restraint strap market. Colin Barnett has found some good news and some bad news. The good news is that the number of manufacturers achieving a 100% success rate has jumped from one in eleven to six in twelve; the bad news is that the overall failure rate of samples remains exactly one in three... Legislcation guidance • The simple truth is that no specific compulsory legislation exists to police the manufacture and use of load restraint equipment.
British Standard BS5759:1987 contains specifications relating to the manufacture and performance of "webbing load restraint assemblies for use in surface transport" and, although compliance with the standard is voluntary, we have used it as the basis for our tests as it constitutes the nearest thing to an industry-wide benchmark.
BS5759:1987 covers the design and construction of webbing and hardware, test procedures, labelling and instructions for care and use. Strength is calculated by the formula that Rated Assembly Strength (RAS) is half of the assembly breaking force.
A European Standard, [Ni 2195-2, exists in draft form: it is expected to follow closely the basic requirements of BS 5759:1987, with some elaboration on testing methods. Use of loadrestraint equipment is largely governed by the general provisions of the Road Traffic Act 1991, although there are other relevant implications under the Health and Safety legislation.
Probably the most useful source of information from an operator's point of view is the Department of Transport's Code of Practice on Safety Of Loads On Vehicles (ISBN 011 550 666 7). This 75-page document is a mine of detail on virtually every aspect of the subject. It is available from HMSO at 29.50 (contact 0171 873 9090). The improved consistency is to be applauded, but it is still disappointing that a third of the straps tested failed to meet the requirements demanded of them, given the implications of their failure.
For the first time we have included purchase costs in the results, disproving the adage that you get what you pay for. The three cheapest suppliers comfortably achieved 100% with all of their samples, while the worst performer, which failed to reach an average of 70% of the rated breaking strain, was the second most expensive.
To ensure total impartiality, our mystery buyer, a Home Counties operator, was given a list of all the strap manufacturers known to us and asked to place telephone orders from 12 at random.
Each order was for three sets of 2 . 5 -tonne Rated Assembly Strength (RAS) straps, 10m long and 50mm wide, fitted with claw hooks at both ends. The RAS is equal to half the Ultimate Tensile Strength (UTS), so a strap with a 2.5-tonne RAS should be able to take a strain of five tonnes.
Although no discounts were requested, it is possible that our buyer was known to some of the manufacturers so the prices charged may have been voluntarily discounted.
When all of the samples were received they were dispatched unopened to our test venue.
Some of the straps included chafing sleeves and/or transport locks, although none were requested.
As in previous years, all of the tests were carried but at the National Engineering Laboratory at East Kilbride. The NEL is an independent facility which car ries out materials testing for a wide variety of organisations, both in the public and private sectors. The testing was wit nessed by the Association of Load Restraint Equipment Manufacturers' nominated representative, Kevin Holroyd. Although Holroyd is employed as the technical manager of one of the strap suppliers, he was not invited to participate until all the straps had been safely received. Test prcscedure • Our testing was carried out in the Solid Floor Room at the NEL. This room has a floor with a heavy-duty mounting point every metre, to which test rigs of all descriptions can be attached. The tests were carried out on a rig consisting of a steel beam attached to the floor, underneath a hydraulic ram acting in an upward direction. The rig is fully adjustable for rate of flow and is attached to a bank of electronic recording instruments.
Our procedure followed the requirements of B55759:1987 which recommends that the test is carried out over a period of around 60 seconds.
Obviously this is only a target figure, as the duration of each test will depend on the failure point. The rate of testing was set at 200mm per minute for each sample.
Each ratchet strap sample was preassembled by joining the fixed and adjustable ends to an overall length of 2.3m, and then winding two complete turns onto the ratchet. This marked the only change from our previous strap tests, which used one and a quarter turns; the change was made for two reasons. Firstly, BS5759:1987 states that testing should be in line with the manufacturer's recommendations; where the manufacturers quoted a figure, it was two complete turns in each case. The second reason was the impossibility of winding exactly one and a quarter turns onto a ratchet with an odd number of teeth.
Once pre-assembled, each sample was attached to the rig by a D-shackle at each end. The shackles were chosen to be a comfortable fit within the radius of the claw hook. The slack was then taken up and the test was ready to commence.
Once the observers had taken cover the rig was set in motion at the pre-determined rate until failure occurred. The loading at the point of failure was recorded and the test was repeated for the other two samples from each manufacturer.
The only task remaining was to convert the machine's readings from kN (kilonewtons) into the kilograms of the manufacturers' ratings. A maximum reading of 5,000kg or more was counted as a pass. Comments • All of the manufacturers were shown their test results prior to publication and invited to comment. Five replied before our deadline, and some pertinent extracts from their comments are printed below.
Spanset's managing director, Tony Eaden, says: "We have no previous experience of a failure at this low level. This maverick result is a one-off and the chance of recurrence infinitesimal."
He added that its supplier will be incorporating a crack-detection procedure into its test routine, and requested that the broken item was returned for a full laboratory analysis.
Dawbarn & Sons, whose product suffered the same ratchet teeth failure on all of its samples, is recalling all ratchets from that batch for replacement, and is withdrawing from sale any unsold ratchets from the batch.
John Wallace, sales manager of Apex Load Control, expressed disappointment with the results, saying: "We will be carrying out our own webbing tests and making whatever changes are necessary."
He also confirmed that a problem with the label material has been identified and replacements are being assessed.
Mike Wildi, sales manager of Load Lok, made the point that unsuitable or non-existent restraint methods pose a greater danger than a lashing strap which fails at 4% less than its declared value.
The last word goes to Tony Beal, which was the only manufacturer to have a 100% success record in our last test, and which produced the best results again this year.
Director David Beal says: "I would like to think that one day every manufacturer would produce securing straps that meet the specification required and also the strengths expected. However, until both the end user and the manufacturers realise the importance of the securing lashings and the direct risks that are taken when corners are cut, then we will continue to read of accidents and the devastating effect on people's lives." US° Art abuse • As well as the usual tests on complete new strap assemblies, CM also arranged for NEL to carry out tests on samples which had been deliberately abused. One strap had a simple knot introduced (of the type created by careless storage) and another had a 2mm cut made on the strap edge.
Both straps, with a nominal UTS of 5,000kg, were known to be capable of withstanding at least 5,300kg.
Surprisingly, the strap with the cut still managed to exceed its nominal capacity, failing at 5,093kg. As expected, the break was at the point of the cut.
However, the really unexpected result, and one which should send shivers through the spine of every operator, was the knotted strap. After some initial tightening of the knot, the strap gently fell apart at just 1,713kg, having lost more than 67% of its original strength.
If just one fact from this test is to be remembered, it should be this one—and it should be passed on to anyone who ever uses load restraining straps.
Findings • The order of testing was determined by nothing more scientific than the random order in which the straps had been unpacked by NEL.
We began to think that all was well with the load-restraint world as the first assembly to fail to reach five tonnes before breaking was the 14th to be tested. Sadly, things went downhill from there as failures became more frequent.
At the end of the test six manufacturers had achieved a full house, while three had a single failure apiece and three failed totally.
The least expected failure was that of Spanset's third sample. Until then their product had been most impressive, with excellent appearance and finish, accompanied by the most comprehensive user instructions in our sample. Spanset's first two samples sailed through the test, but its third suffered a failure of one side of the hook near the claw bend.
We have deliberately avoided pronouncing judgement on compliance with BS5759:1987. Some of the results would been based on questions of interpretation, such as in the case of labels which carried a tradename as required by the Standard, but no other practical means of contacting the manufacturer. The other main category of non-compliance, quoting Rated Assembly Strength in kg rather than tonnes, could have been seen as a pedantic detail. Delta force" • One point which we had demonstrated to us during our testing was the effect of choosing the wrong type of strap attachment from the three that are commonly available.
The solid D-shaped rings, known as "delta" rings, are designed to be used with rope hooks. Claw hooks are only intended for attachment to chassis rails or tie-down rings of adequate strength. The third type, with a wide rectangular shape, should only be used for attachment to body side raves.
Although the claw hook appears to form a closed ring, and may be welded, the closure is definitely not designed for fixing to rope hooks. Doing so with a welded hook is likely to break the weld, while an unwelded hook will simply separate.
In either case, the assembly is almost certain to fail well before the required strength is attained. The moral, as always, is to use the right tool for the job.
Summary • With the exception of the single (hopefully one-off) example from Spanset, and all of the samples from one other manufacturer, all failures were within 10% of the target loading. Clearly, with some fairly minor improvements in material specification and quality control, the overall picture could have been much more encouraging.
Although safety is the paramount issue in this test, we were extremely surprised by the cost of the straps— the delivered cost of the three samples varied from £41 to £91. Our surprise was not just at the disparity of the cost, but at the way in which cost appears to have no bearing on quality.
The improvements achieved by the majority of manufacturers is heartening, but must be set against the fact that a minority of the products on the market can only be described as accidents waiting to happen.
The worst thing is that operators have no way of knowing what they're buying. Compliance with BS5759:1987 and membership of ALREM may indicate that manufacturers have the best of intentions, but doesn't tell the whole story.
Our earnest hope is that the progress made so far will continue. Loading straps are hardly the most glamorous items of equipment but they are an essential component of a safe haulage operation.