Most EWP owners are familiar with the controls and the compliance requirements, but fewer have a clear picture of the hydraulic system that actually moves the machine. Understanding the main components — and what each one does — makes it much easier to recognise when something is developing, communicate with a technician, and make informed decisions about repairs. This guide covers the hydraulic system in plain language, without the engineering detail that only a designer needs.
What hydraulics do in an EWP
The hydraulic system converts engine or motor power into controlled movement. Oil — under pressure — is pushed from the reservoir through the circuit to cylinders and motors, where that pressure does work: extending a boom, rotating the platform, driving wheels or tracks. Because oil is incompressible, it transmits force precisely and can hold a load without the machine running continuously.
That load-holding ability is a key reason EWPs use hydraulics rather than mechanical linkages for boom movement. When an operator stops mid-extension, the hydraulic circuit holds the platform in position without the engine needing to work to keep it there.
Main components
- Reservoir — the tank that stores hydraulic fluid. It feeds the pump and allows returning fluid to settle and cool before recirculating. Low fluid level is one of the most common and most preventable causes of hydraulic problems.
- Pump — driven by the engine or electric motor, the pump moves oil from the reservoir into the circuit under pressure. Pump wear or cavitation (drawing in air) is a leading cause of lost hydraulic performance.
- Control valves — direct oil to the correct cylinder or motor when an operator activates a function. A valve that sticks, wears or develops internal bypass causes unpredictable or sluggish movement.
- Cylinders — convert hydraulic pressure into linear movement. The main boom, secondary boom, jib and levelling system each have one or more cylinders. Cylinder seals are wear items; when they fail the cylinder drifts or loses force.
- Load-holding valves — lock the cylinder in position when no control input is given, preventing drift. These are safety-critical components and are checked as part of every compliance inspection.
- Hoses and fittings — carry oil between components. They are rated for pressure and flex-cycle life; a hose failure is typically sudden and causes loss of the hydraulic function it serves.
- Filters — remove contamination from the oil. Blocked or bypassed filters allow abrasive particles to circulate, accelerating wear on pumps, valves and cylinders.
Why hydraulic fluid condition matters
The fluid itself is easy to overlook because it is not visible during normal operation, but its condition directly affects system life and performance. Over time, hydraulic fluid degrades thermally, picks up water contamination, and carries fine metallic particles from normal wear. As the fluid degrades it loses its viscosity stability, lubrication properties and ability to resist oxidation.
Fluid that is changed on schedule and tested for contamination will significantly extend the service life of every component it touches. Fluid that is never changed — or that is topped up repeatedly without addressing why the level is dropping — will shorten it.
What hydraulic service involves
A routine hydraulic service typically includes: fluid and filter replacement, visual inspection of hoses, cylinders and fittings for leaks or damage, pressure testing to confirm the circuit is operating within design parameters, and a function test of load-holding valves and safety devices. The scope varies depending on the machine's age, hours and inspection history.
A hydraulic repair goes further — a specific fault has been identified and needs to be rectified. This might mean replacing a cylinder seal kit, rebuilding or replacing a control valve, fitting a new hose assembly, or replacing the pump. The repair is followed by pressure testing and a full function test before the machine is returned to service.
This guide is general information prepared by EWP Australia and is grounded in publicly available Australian Standards and Safe Work Australia material. It is not a substitute for the current published edition of the relevant standard or for site-specific engineering advice. Always work from the current standard and consult a competent person for your specific equipment and application.