Apparatus & Equipment, Extrication Zone, Tools & Equipment

The Ins and Outs of Hydraulic Rescue Tools

Issue 11 and Volume 172.

TRAINING NOTEBOOK ❘ By STEVE SHUPERT The path taken by hydraulic fluid is called a hydraulic circuit. For hydraulic fluid to do its work, it must flow through the pump,valves, hoses, and tool and then return to a reservoir. The fluid is then filtered, given a chance to cool, and repumped. Rescue tools typically have open center circuits, using pumps that supply a continuous flow. The flow is returned to the tank through the control valve’s open center—that is, when the control valve is centered, it provides an open return path to the tank. Pumps create flow—not pressure—and pressure is a by-product of the hoses, valves, and so on. To illustrate this point, a pressure gauge attached to the discharge line reads the resistance to the pump’s flow. When the control valve is actuated, it routes fluid to and from an actuator and tank to the tool. The fluid’s pressure will rise to meet any resistance since the pump has…

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