2 - TCA spa

Figure 8. Pressure Compensated Flow RegulatorAdjustable OrificeSequence Valvethe other end of the spool in the spring chamber. If flow acrossthe orifice increases due to a reduction in the downstreamworking pressure, then the pressure drop would increase andthe sequence valve open further to by-pass excess flow to tank.The valve will therefore seek to maintain a constant flowirrespective of changes in working pressure.A final example of an innovative use of a sequence valve is as aload sense compensator (figure 9). By feeding a load sensesignal into the spring chamber, the setting of the valve can beraised. This ensures that the pump will only ever see a pressureequivalent to the working pressure, plus the setting of the valve.This pressure can be limited by using a pilot reliefvalve on the drain line. The flow into the spring chamber has tobe restricted for this to work, but a millimetre orifice normallyworks for me!There are many other potential uses for this valve byusing the drain port as a remote control port. Why limit theutilisation of problem solving tools at your disposal by sticking toa name? Hydraulic valves can be versatile. Think hydraulicsbefore you think description and look to performance, not tocatalogue claims. Use science and understanding first and theproduct second but always consult the valve manufacturerbefore going too far, as all valves will have their limitations -some of which are far from obvious.Figure 9. Load Sensing CircuitShuttle valve, senses thehigher pressure in the 2service lines.OrificeSequence valve, reacts to serviceline pressure dumping excess flow.Solenoid valve, unloads thesystem by venting the springchamber of the sequence valve.Relief valve, limits maximum pressurein the system by limiting the pressure inthe sequence valve spring chamber.