Hydraulic oil and filter change procedure

What’s inside

1. 1

   Check the fluid specification

   Check the specified fluid type, viscosity grade, quantity and target cleanliness code in the machine manual, and have the fluid, filter elements and breather ready.

   Verification5 min

   Tools: Machine manual, new fluid, filter elements, breather

2. 2

   Lower loads and depressurise the system

   Lower every cylinder and attachment to rest or block it mechanically, stop the pump and operate the controls to relieve trapped pressure. Discharge accumulators to zero with the manufacturer’s method and confirm on a gauge.

   Action15 min

   Tools: Pressure gauge, mechanical blocks

   Risks: HIGH RISK: accumulators and trapped circuits stay pressurised after shutdown. Sudden release can move loads or inject fluid through the skin.

3. 3

   Isolate the power unit

   Isolate and lock out the pump motor following your lockout / tagout procedure and check it cannot start.

   Action10 min

   Tools: Lockout devices

   Risks: Unexpected start-up re-pressurises the circuit.

4. 4

   Drain the reservoir

   Drain the fluid into a suitable container, warm if it is safe to do so, together with any low points the manual specifies.

   Action30 min

   Tools: Drain pump or container, absorbent

   Risks: HIGH RISK: hot fluid causes burns; spilled fluid is a slip hazard.

5. 5

   Clean the reservoir

   Remove sludge and water, wipe the inside with lint-free cloths (never shedding rags) and clean the suction strainer. Inspect the reservoir for rust or damaged baffles.

   Action30 min

   Tools: Lint-free cloths, suction pump, torch

6. 6

   Replace the filter elements

   Replace the return, pressure and pilot filter elements with the specified rating, lubricating the seals with clean fluid. Check the clogging indicators reset.

   Action20 min

   Tools: Filter elements, filter wrench

   Risks: Filter housings can hold residual pressure; open them only after depressurisation.

7. 7

   Replace the breather

   Fit a new filter or desiccant breather so that dust and humidity cannot enter the reservoir when the level moves.

   Action5 min

   Tools: Breather

8. 8

   Refill through a filter cart

   Fill with the specified fluid through a filter cart, never by pouring straight from the drum: new fluid is often dirtier than the system’s target cleanliness. Fill to the level mark.

   Action30 min

   Tools: Filter cart, new fluid

9. 9

   Bleed air from the system

   Remove the locks following your lockout procedure, start the pump at low pressure and cycle every actuator slowly through its full stroke several times, opening bleed points if fitted, until movements are smooth.

   Action20 min

   Risks: HIGH RISK: actuators move while bleeding; keep everyone clear of the machine’s movements.

10. 10

    Check the fluid level after cycling

    With the cylinders in the position the manual specifies (usually retracted), check the level and top up through the filter cart.

    Verification5 min

    Tools: Filter cart

11. 11

    Check for leaks at working pressure

    Run the system at normal working pressure and check fittings, filter housings and hoses for leaks. Use a piece of cardboard, never your hand, to look for pinhole leaks.

    Inspection15 min

    Tools: Cardboard, torch

    Risks: HIGH RISK: a pinhole jet can inject fluid under the skin; any injection injury needs urgent medical treatment.

12. 12

    Take a cleanliness sample

    Optional: after about an hour of operation, take a fluid sample for particle count to confirm the system has reached its target cleanliness.

    Measurement10 minoptional

    Tools: Clean sample bottle, sampling valve adaptor

13. 13

    Record the work and dispose of waste

    Record the date, fluid grade and quantity, filters fitted and any findings. Dispose of used fluid, filters and rags as hazardous waste.

    Action10 min

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