Making Sense Of Load Sense

Load sense systems.?

What are they? Why do we use them? And how do they work??

Today we’ll be giving you a very basic answer to some of these questions in the hopes that you can better understand this part of hydraulics equipment and know when it might help you create solutions to problems, or where it may even be causing the problem.?

So let’s dive right in.?

What are load sense systems??

Load-sensing describes a type of variable pump control used in open circuits. It is also termed this because the load-induced pressure downstream of an orifice is sensed and pump flow is adjusted to maintain a constant pressure drop (and therefore flow) across the orifice.

The orifice is typically a directional control valve with proportional flow characteristics, but a needle valve or even a fixed orifice can be employed, depending on the application.

Why do we use them??

In hydraulic systems subject to wide fluctuations in flow and pressure, load-sensing circuits can save substantial amounts of input power. In systems where all available flow is continuously converted to useful work, the amount of input power lost to heat is limited to inherent inefficiencies.

In systems fitted with fixed displacement pumps where 100 percent of available flow is required only intermittently, the remaining flow not required passes over the system relief valve and is converted to heat.

This situation is compounded if the load-induced pressure is less than the set relief pressure - resulting in additional power loss due to pressure drop across the control valve.

A similar situation occurs in systems fitted with pressure-controlled (pressure-compensated) variable pumps, where only a portion of available flow is required at less than maximum system pressure.

A load-sensing controlled variable pump largely eliminates these inefficiencies.

How do they work??

The load-sensing controller responds to the increase in load pressure by slightly increasing pump displacement (flow) so that pressure upstream of the direction valve (or other opening) increases by a corresponding amount. This keeps the pressure drop across the directional valve constant, which keeps flow constant.

High-end load-sensing directional control valves feature a pressure compensator at the inlet to each valve section. The section pressure compensator works with the spool-selected opening to maintain a constant flow rate, independent of the pressure variations caused by the operation of multiple functions at the same time. This is sometimes referred to as “sensitive load-sensing”. And is better used in more complex systems where sections need to work independently.?

If you want to explore this topic in more depth watch the training we recorded for this topic HERE.?

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