At the tipping point of cylinder safety

A failed lifting cylinder on a tipper truck will certainly disrupt operations, may be expensive to repair and could even endanger life. Nick Sandbrook, testing manager for Edbro tipping cylinders, says rigorous testing during design and manufacture is the only way to prevent such scenarios and outlines his company’s demanding regimes.

The lifting cylinder of a tipper truck is exposed to regular cycles of heavy loads. Yet it is expected to perform without fault over a long working life. In an industry where profit margins are narrow and equipment failure can be catastrophic, the quality of such equipment must never be in question. Thus, the testing standards set by Edbro for its tipping cylinders are designed to ensure safe, reliable performance under all conditions.

For Edbro products, the ultimate aim is to create ‘fit-and-forget’ products that, once installed, require no servicing throughout a long working life other than an annual oil change. To achieve this level of reliability, Edbro, part of the JOST World, tests every design before production and every cylinder before dispatch, with the pass level far higher than is required in the field. In essence that is how we ensure long term performance and protect our reputation as a top-quality manufacturer.

Cylinder testing comes in two regimes, design and production. When a cylinder is being designed the principle objective has to be a strong reliable cylinder that will perform faultlessly throughout a long demanding working life. The idea behind the test procedure used by designers is to simulate the most extreme working life imaginable. The tests are long, to simulate many years of use, and they create harsh working environments to include shock loads, impacts and side forces. In effect they accelerate the test piece through the most appalling working life conceivable and only pass it if it is still going strong.

A different philosophy is required in manufacturing. Here the design has been proven, so the requirement is to test the quality of build, looking for minor imperfections that could compro-mise performance. The multiple Edbro tests carried out during production check each cylinder for pressure, functionality and leakage, and also check each component. The objective is that any cylinder made by Edbro and passed by its test regime can be expected to perform flawless-ly, no matter how arduous or long its working life.

Designing in quality
Edbro’s research and development program is world class and uses multiple specialist test rigs so that every aspect of each design can be fully tested. For example: an endurance rig is used to cycle test cylinders across their full stroke length for extended periods; typically this could be 10,000 strokes or more over a number of weeks. This is the equivalent of a long working life and at the end of this test a pass certificate is issued only if there is no wear or damage of any sort.

Fatigue tests check all the components for signs of progressive wear or other failure modes brought on by long term operation, while dynamic load tests are constantly undertaken on cylinder casings, telescopic tubes, trunions, brackets, seals and all the individual components of a cylinder.
Other test rigs check for specific issues. A side load test rig simulates the effects of asymmet-ric loads, such as when a truck is parked on an uneven surface and the cylinder is extended. Here oil leakage and reduced alignment of the telescopic tubes being carefully monitored. Similarly buckling tests are a vital part of the test regime and ensure each cylinder design is able to accommodate the loads it is expected to encounter in the field without sudden catastrophic failure.

Tipper trucks operate in a rough world, so Edbro has devised an impulse rig which monitors each design’s ability to withstand sudden impacts, pressure surges and similar shock loads.
The ultimate test is over-pressure testing. Edbro will not pass a cylinder unless it has proven its ability to withstand up to 500bar for an extended period without failing. It is unlikely that a tipper cylinder will ever be subjected to such a pressure overload during its working life, but Edbro cylinders offer the comfort of knowing that – if necessary – they can.

Testing throughout production
With the design proven, Edbro continues testing on the production line. The basic test is a functional one, making sure each cylinder extends and contracts smoothly over its full length, time and time again. During this process the cylinder is pressurised to 150 per cent of its working pressure, to ensure that it is operating with significant safety margin.
However, there are a number of further tests, every one of which has to be passed with flying colours. Every seal and valve is visually checked for oil leaks, while pressure decay (would also be a sign of leakage) is also monitored. Every component is individually checked for quality; telescopic sections are minutely inspected for surface blemishes, marks and imperfections – not even the paintwork escapes the eagle eyes of the Edbro inspectors.

Setting the standard
All this may seem like Edbro take testing to an extreme level, but we aim to be the benchmark for long- term reliability. Cylinders that fail will almost always do so when they are tipping out a load. The load will be extremely heavy so a cylinder failure could lead to the tipping trailer collapsing back down onto the bed of the truck and causing untold damage and risking serious injury to the operator and nearby pedestrians.
In the hectic world of tipper operations, it is all too easy to assume that quality, reliability, en-durance and safety are built into every part of every vehicle. Edbro’s insistence on testing to supreme levels means its cylinders can be relied upon to work faultlessly no matter how long or how hard their working life.

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