Unloading Valve Basics 

Thanks! We don't use any off-the-shelf software - our programmers and artists make the simulations from scratch. You can read more about them here on our company site: cdiginc.com/live-schematics

Hi Ichigo. Our team of artists and programmers make these simulations from scratch. While it might not help with your assignment, companies can hire us to produce a Live Schematic for their equipment: www.carldyke.com/live-schematics Good luck with your assignment.

LunchBox Sessions Well, thanks for the quick response.

Generation 5th please see our video "How to Interpret Pressure Valves".

Thank u

You could put a check valve on that low flow pump outlet, yes. In this case the check valve on the high flow pump is serving a very special purpose - to help operate the unloading valve. Without the check valve, both pumps would flow to tank when the unloading valve is triggered. With both pumps unloading, pressure would fall, and the unloading valve would close. Then pressure would build once again, and the system pressure would oscillate - not good. The application is common for a press type of machine, where the high flow is needed during the initial 'motion' stage, and then when the press is doing hard work near the end of stroke, the high flow pump is unloaded, and only a low flow is used, to finish the press cycle at high pressure. Thanks for the questions. - Carl

We've got some information about how we make these simulations here on our website: www.lunchboxsessions.com/help/what-software-do-you-use-to-make-the-simulations

Great question Vijay. The two pump scenario with unload valve in the lesson is popular for a high/low circuit, sometimes know as fast-approach, slow-feed, or motion-and-hold. One example is a filter press where both pumps (one with noticeably higher displacement) help to close up the press (motion control application) but once closed, the large pump is unloaded, while the very small pump is used to maintain a critical clamping pressure (hold function) and make up any internal leakage. A small displacement pump at high pressure requires far less input energy than a large pump at high pressure, flowing mostly over a relief valve during clamp dwell time. Unloading valves are sometimes used with a single pump. They are often then referred to as an accumulator charge valve, where the single pump is unloaded once a sufficient charge volume of oil (detected by pressure switch at accumulator) is present in the accumulator. The single pump displacing it's full volume but at very low pressure through an unloading valve is again saving lots of input energy. The amount of input energy (eg. electricity consumption) for a hydraulic system is as you know, a combination of both pressure value and displacement (flow). Feel free to respond again if I am not adequately addressing your question.

GREAT REPLY FAB #LunchBox suggestions * please add more circuits that will surely helpful to students and professor. * add numerical treatment for different valves so student can easily differentiate difference.