Hoses are one of the most important parts of any hydraulic system. In the worst case scenario, problems with hoses may bring work on a jobsite to a halt for one day or they can destroy the hydraulic system of a carrier. Saving 50 euros may cost 100,000 euros when things go wrong. It is always recommended to use original hoses provided by the manufacturer.
The quality of hydraulic hoses and connections must fulfill the demands of surrounding conditions, oil flow and pressure, oil quality and the demands of adaptation. For carrier safety the rubber quality inside the hose must be able to withstand the mechanical stress of oil flow and pressure together with constant bending when hoses move. Small pieces of rubber will clog the filters and in some systems they may jam the valve block and damage the hydraulic pump. The rubber must be suitable for use with the chemicals used in hydraulic oil over a wide temperature range to avoid foreign chemicals dissolving in the oil. Minor changes in oil consistency may change the characteristics of the oil and cause premature wear and damage to the carrier and the attachment. Some biodegradable oils in particular may have chemicals that can damage the hydraulic system.
Inside the hose there are normally textile and steel weave layers and radial steel wire reinforcement to withstand the pressure inside. This structure is designed to handle a certain constant pressure and the peaks that are possible in that pressure range. The maximum working pressure is printed on a hose and it should never be exceeded.
The outer surface of the hose holds the structure together and protects the hose from external stress and conditions. It should be suitable for the typical conditions of an application and there is a wide selection available for all demands. Hoses can be protected against external wear and damage by steel or plastic springs or a textile
The inner diameter of the hose must be big enough to cope with the desired oil flow. Hoses that are too small will increase the flow resistance and pressure inside the hose and eventually increase the oil temperature. These factors will cause attachment malfunctions and leaks in the hydraulic line.
The hose length must fit the setup of connections on the attachment and carrier in any possible movement of the attachment. A hose that is too short will break up and damage the connections, a hose that is too long may be damaged easily and will place extra stress on connections. Check the correct length when the attachment is adapted on a carrier.
There are basically two kinds of couplings, screwon and quick couplings, and countless variations on them. The rule of thumb for couplings is – the simple the better. Screw-on connections are cheap and they are easy to seal to maintain the pressure without leakage. Best of all, they won’t choke the oil flow.
Quick couplings are easy to connect and disconnect but they have some disadvantages. In most of them the inner diameter is smaller than the pipeline and they choke the oil flow which often causes the attachment to malfunction. Proper sealing in high pressure lines is challenging and after numerous connections they may start to leak.
Before choosing the coupling type it is good to consider if it is really necessary to have quick couplings. If an attachment will be mounted on the same carrier most of the time there is no reason to choose quick couplings. Whatever the connection type it is always important to keep the connections clean and plugged when they are disconnected to prevent dirt and moisture from entering the hydraulic system.