Screwing together the threaded connections of these components is mostly performed by hand, using two fingers ( preferentially without the use of a wrench ), also while the hydraulic system is in operation. To make this possible without important losses of fluid, certain working criteria has to be observed. In addition the tasks will be determined by the necessity to achieve an optimal operating safety, as it is a very useful accessory to rationally perform system checks and maintenance works, as long there are no standstills, that may cause accidents and expensive operating interruptions.

To perform thorough air venting works, a suitable test-hose is laid between the tank ( or to a drain or a return line ), and the high pressure line that has to be vented. In a similar way it is possible to extract fluid samples, to verify its state, directly from the actuator supply line, where there is sometimes insufficient interchange of fluid.

The test-hoses are comparable to electric cables and can be laid as easily. However, hoses represent most likely the weakest element of a hydraulic system. These should therefor have maximal resistance against both hydraulic and mechanical stress conditions. That way it is possible to limit respective risks.

The use of test hoses as connection lines for instruments and in miniature hydraulics is very comfortable and can reduce assembly costs significantly. Test-hoses also dampen pressure peaks of the system and avoid the transmission of vibrations to the measuring instruments.