Test Methods for Flow Sharing Directional Valves

This paper presents the results of a study regarding procedures to qualify Load Sensing Flow Sharing (LSFS) distributors especially under dynamic conditions. In spite of their popularity, as they enhance control of loads solving problems of interference even in saturated pump condition, no normative reference exists addressing the performance of LSFS systems. For this reason, a set of test methods aimed at evaluating and comparing the different solutions available have been developed. These methods can be classified according to the type of load, imposed by valves or by actuators. In the first case the loads are predominantly dissipative, in the second case the inertial component is predominant. The test method proposed allows the evaluation of the system dynamic behaviour according to response time, undershoot and overshoot of physical variables. The first test with valves is a sudden pressure variation on one out of two active sections. The objective is to evaluate the behaviour of the device when the generation of the LS signal switches from one section to another. The second test with valves is the rapid actuation of a section. It evaluates the behaviour of the system with sudden variations of flow rate. This test it is intended to induce a transition between saturation and non-saturation. The tests with inertial loads consist in the actuation of spools in order to study the control of purely inertial loads as they can induce dynamic instability of LSFS systems and affect their performance. The paper presents the proposed testing procedure together with a set of experimental data on their application.