2 years ago

MDA Technologies 3/2014

MDA Technologies 3/2014

Reliable Hydraulic Lines

Reliable Hydraulic Lines Larger, stronger, greater capacity: the demands on units are rising inexorably in all industrial hydraulics applications. Hydraulic lines also have to keep pace with these changes. However, a visual inspection of the hose or finished line is not enough to gauge the level of care which has gone into its manufacture or determine the tests and safety checks which it has undergone. That is because compliance with the relevant DIN standards is not yet particularly meaningful. As a result of their very loosely drafted specification, it is perfectly possible, even with a standard-compliant hose, for the inner hose, for example, to consist of a lower-quality material than the visible outer hose, which can result in quality problems later for the user. At best, the manufacturer’s logo gives an indication of the tests and the care applied during manufacture. This means it is all the more important for purchasers to be able to rely on their supply sources. Insisting on hoses and lines from a certified production source with a supply chain which is also certified is a means of avoiding risks. Thus, hose and hose assembly production at ContiTech is based on the TS 16949 quality management system and the ISO 14001 environmental standard. Specified test schedules All the company’s hoses meet DIN standard specifications as a matter of course. However, ContiTech Fluid Technology takes the very loosely drafted standards and tightens them substantially. At ContiTech, for instance, the materials of which the outer and inner rubber plies have to be composed and the number of threads to be used for reinforcement are specified absolutely precisely. The hoses are ordered in accordance with precisely defined test schedules which specify each of these properties. Even before the first shipment arrives in the plant for assembly, the hose is subjected to an appropriate fundamental approval test on the manufacturer’s premises. Tests are conducted in ContiTech’s labs and test facilities to determine whether the hose meets the specified requirements, has the desired impulse resistance and passes the burst tests. UV resistance, abrasion strength and media resistance to, for instance, hydraulic oil and gasoline are also tested. Here, too, the testers apply significantly more stringent benchmarks than the DIN standard would require. With reference to the impulse resistance, for example, these benchmarks are up to a third higher than the specifications of DIN 6803. Depend- 46 MDA Technologies 3/2014

Machine Elements 01 A hydraulic line is only as reliable as its weakest link - for that reason ContiTech applies the highest standards throughout the supply chain 02 The demands made of industrial hydraulics solutions are becoming more and more stringent ing on the customer’s requirement, resistances of up to 3 million impulses are even possible. Once the hoses intended for use as reinforcement finally arrive in the assembly plant, they first undergo a goods-inward inspection. Compliance with the original approval requirements is regularly checked as part of a specified requalification system for series production monitoring. In this, the hoses supplied must from time to time pass the same tests again which they underwent at the approval stage. This ensures that a consistently high quality is always supplied and that the suppliers always manufacture to the same high standards as at the start of an order. Check random samples In the plant the fittings manufactured there which are crimped onto the hoses to ultimately form hydraulic lines are subjected to the same approval tests as the hoses of external suppliers. Here, too, DIN ISO 6803 forms the basis for the tests – and is then again extended to include the significantly higher standards applied by ContiTech. Because the finished line is only as strong as its weakest link. For that reason it is vital that the fittings are every bit as good as the hoses. The same applies to the finished crimped hose assembly. It is regularly subjected to rigorous testing in accordance with the internal requalification system for series production monitoring in order to rule out quality fluctuations in the material and during the production process. Statistical process checks ensure that important features such as the crimp dimension and the friction fit of the connections between the hose and fitting do not change by more than a narrow measurement. This is guaranteed, on the one hand, by constantly monitoring the machine capability, which involves verifying the reproducibility of the production results, and, on the other hand, by continually conducting random checks of the finished components. Even once the lines have arrived on the customer’s premises, ContiTech’s quality control measures are still far from at an end. Constant observation of the market permits ongoing conclusions to be drawn about the quality situation and also helps identify installation and application errors by the customer. Feedback, such as information on line failures, is collated and statistically evaluated. If clusters are noticed, these are examined more closely. Thus it has proved possible in the past to resolve problems by correcting a wrong fitting position adopted by the customer, for instance too tight a bending radius. Problems can be resolved quickly If, despite all the care taken, complaints do occasionally occur, ContiTech is able to trace the smallest individual part – for example, down to the supplier of the turned parts – of every batch. This means problems can quickly be contained and resolved. But the hydraulic lines are not the only components that have to keep pace with the constant rise in requirements; this same demand is made of the connections between the assemblies and the central hydraulic unit. Depending on the application, both snap-on and screw couplings are used as connectors. It is absolutely vital that nothing goes wrong at this crucial junction between the hose and the fitting. ContiTech also has rigorous specifications for these rubber/metal connections. After all, a hydraulic system is only as strong as its weakest point. How the hose has to slide between the nipple and the sleeve of the fitting and then be firmly crimped into place with a hydraulic press is therefore clearly regulated. This ensures that the connection is absolutely leakproof and that precise functioning of the hydraulic application is guaranteed. About Company name: ContiTech Business: Fluid Technology Headquarters: Hanover, Germany Turnover: € 3.7 bn Employees: 30,000 Products: components like hoses, belts, mounts and systems for the automotive industry and other important industries MDA Technologies 3/2014 47


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