This not only can result in unstable system pressure but in some cases can also void any warranty on the pump.Ī typical configuration of a pressure-compensating pump is shown in Figure 1. The most common reason to adjust a load-sensing valve is because someone unfamiliar with the pump has mistakenly attempted to set the maximum system pressure by adjusting the load-sensing valve instead of the compensator. In most pumps, the factory preset is approximately 200-300 pounds per square inch (psi). The load-sensing valve is factory preset and normally does not need to be adjusted during the initial pump setup. The compensator valve is closer to the pump. When the pump-loading valve is shifted, the system pressure drops to the much lower load-sensing valve setting.Ī load-sensing valve usually is smaller than the compensator valve and typically mounted directly on top of the compensator. Most load-sensing systems have a pump-loading directional-control valve of some sort that can place the system in an idle condition until it is necessary to move another load. When the flow is blocked in this fashion, the system pressure can build no higher than the setting of the compensator, but until another load is to be moved, there is no need for the system pressure to be kept so high. Eventually, the cylinder reaches the end of its stroke, and flow is blocked. For instance, as a cylinder is extended, pressure in the system will build as necessary to move the load. Whenever the system is moving a load, the high-pressure adjustment limits the system pressure. The two separate pressure adjustments allow setting the compensator valve to the required maximum system pressure and the load-sensing adjustment to a much lower standby pressure. This can conserve energy and reduce heat and wear in systems that spend a significant amount of time in an idle condition. The second adjustment is called either a “load-sensing” valve or “flow-compensator” valve.Ī load-sensing pump is designed to reduce its pressure to a much lower standby level whenever the system is idle. This type of pressure-compensating pump is called a load-sensing pump. The two adjustments can look nearly identical. However, some pressure-compensating pumps have two valves mounted on the pump body.

With all flow blocked and the system idle, the compensator valve is adjusted to the desired pressure. While a pressure-compensating pump is efficient, the standby pressure remains high.Īdjusting a pressure-compensating pump is quite simple. It will stroke only a very small amount or whatever is required to maintain the compensator setting in the line, overcoming any system bypassing or leaks. When the system is stopped completely, the pump stroke is reduced almost to zero. Whenever the system flow needs to decrease (such as when one or more actuators are stopped), the pump stroke is reduced. Whenever more flow is demanded by the system (such as would occur when an additional actuator begins to move), the pump will increase its stroke to meet the new flow demand. Once the compensator setting is reached, the pump will be de-stroked to deliver only the amount of flow that will maintain the compensator setting in the line. The compensator is adjusted to a pressure somewhat higher than that required to move the system’s heaviest load.Ī pressure-compensating pump will deliver its maximum flow until the system pressure reaches the compensator setting. Pressure-compensating pumps are designed to deliver only the amount of flow required by the system to maximize efficiency and avoid heat generation.

The most common type of variable-displacement pump is the pressure-compensating pump. This usually means the system has several actuators and, depending on the current cycle of the machine, the number of actuators moving at a given time will fluctuate. Variable-displacement pumps are used in hydraulic systems where the flow requirements vary.

Ram pressure settings