July-August 2021

HYDRAULICS 26 HYDRAULICS & PNEUMATICS July/August 2021 www.hpmag.co.uk abrasion-resistant sleeve or hose guard, but this option considerably increases the assembly costs and can complicate hose installation in the application. In addition to selecting abrasion-resistant hose covers or accessories, the hose routing can also have an impact on hose abrasion. Use clamps to support long hose runs or to keep hoses away from moving parts, taking special care to allow for volumetric expansion. Hoses that bend around a portion of the machine frame should be assembled with enough length to avoid rubbing over a machine corner. And it’s worth noting that hoses should never be clamped to the machine frame, which could restrict expansion in the curves when the hose is pressurised. Proper assembly A user can procure the most premium and highest performing hoses and couplings in the world, but if they’re not assembled correctly then they’ll never realise the value. Proper assembly has several components – qualified hose- coupling interface, assembled by a trained technician, and with a verified crimp diameter. By qualified hose-coupling interface I mean that the specific hose and specific coupling are verified to work together. The verification is more than just crimping to a certain crimp diameter – it should be verified by burst and impulse testing across a range of crimp diameters to account for hose and coupling manufacturing variation as well as crimper and die tolerances. The testing should mimic the intended application, particularly the temperature. A hose- coupling interface may work well at standard 100degC operations and then not perform at all at elevated temperatures above 120degC. Further, hoses are not all the same. Even though hoses from different manufacturers may meet the same performance criteria, the properties of the compound affect the robustness of the hose-coupling interface. The thickness of the rubber materials and the placement of the reinforcement material can change the crimp dimensions as well. Likewise, couplings from different manufacturers are not necessarily equivalent. They may be made from different grades of steel, different material hardness, and include features, such as serrations, that are dimensionally different, significantly impacting the quality of the hose-coupling interface. Even the radius or heights of these features can significantly impact assembly performance. A trained assembly technician is also critical to the assembly process. She or he must be trained to select the proper hose and couplings, cut the hose to the right length, remove debris and contaminants from the inside of the hose, ensure full coupling insertion onto the hose, select the appropriate crimper setting, and place the assembly properly in the crimper dies… and they must do all of this safely. Finally, after the assembly has been made, the crimp diameter on each end of the assembly must be verified for proper crimping. This measurement is often performed with calipers and compared to a qualified crimp diameter range. Some systems also use a go-no go gauge to verify the crimp by reviewing either the crimp diameter or the stem collapse. Smart crimpers are gaining popularity in the market. These crimpers make operator training and quality assembly easier by mistake-proofing various steps in the assembly process. Smart crimpers, such as Gates GC20 Cortex crimper, typically include the crimp settings in an on-board computer to eliminate the need to reference the crimp setting and program the crimper. While it takes years to become a hydraulics expert, attention to several important details can mitigate many hydraulic system errors, avoiding potentially expensive – or worse, dangerous – fluid power faux pas. www.gates.com 5. Signs of wear: Cover cracks caused by ozone. 6. Use clamps to prevent abrasion damage. 7. Allow for volumetric expansion in hydraulics hoses. 8. Proper assembly: Cross-section of the hose-coupling interface. 9. Crimp diameter measurement with calipers.