Hydraulic safety - 5 tips for before, during & after maintenance

May 26, 2020

Working with hydraulic systems requires a sound understanding of how hydraulics operate and what could happen if any part of the circuit is adjusted or replaced. Maintenance of hydraulic systems should be performed by knowledgeable, trained technicians. Here are some things to keep in mind in order to safely and efficiently work on hydraulic systems...

Gain the knowledge

Before touching anything on a hydraulic system, find the circuit drawings for that piece of equipment. Look over the circuit and identify the location and function of every component. First, you need to understand how the circuit is supposed to work. Then identify how the current system is behaving differently from how it is supposed to work. This can save a lot of time compared to the shotgun approach, i.e. changing or swapping everything in the circuit.

Identify and address residual energy sources

Before locking equipment out, think of where residual energy sources will be in the system. For example, a cylinder may be holding up a load even with the hydraulic pumps shut off. Disassembling equipment that is still under load conditions is a serious mistake. Take all appropriate actions to eliminate these potential energy sources an maximize safety, by controlling equipment to a zero energy state and/or using mechanical means to secure equipment in their current positions.

Remove air

If hydraulic components are taken apart or replaced, it is necessary to purge the hydraulic lines of air. In the case of cylinders, the cylinder should be refilled with oil if possible before starting up machinery. This is to prevent unsafe sudden uncontrolled movement when the cylinder fills up with oil during operation (due to the compressibility of air). This is one reason large cylinders are usually connected with backpressure circuits, to eliminate air on the nonpressurized end of the cylinder. If this is not possible, the system will need to be cycled on and off to work out the air. The best place to bleed air from the system is by using bleed valves close to or on the cylinders.

No debris

Always try to keep dirt and debris from getting into hydraulic components. Hydraulic valves such as proportional and servo valves have very small orifices in them which can easily plug up. Cover the ends of oil lines when disconnected from their components. Wipe the areas around valve panels with a lint free cloth before removing parts.

After maintenance

Verify that the equipment area is clear before restarting the hydraulic pumps. Once the equipment is back up and running, check for smooth operation and any leaks in the system.

For assistance with your hydraulic maintenance, contact your Valmet representative.