Hydraulic Maintenance Checklist

Importance and individuality of hydraulic maintenance schedules

The best schedule for preventive maintenance of individual machines can only be determined over time by understanding the usage and operating conditions of the various hydraulic components. For example, an industrial piston pump might only need to be replaced after 10,000 hours of full load running while a mobile pump might need replacing after 1000 hours of full-load operation. The difference is primarily due to design and operating conditions although good maintenance and fluid quality will have a major effect.

Therefore the following schedules are intended as guidelines. Experience and operating conditions will determine actual schedules. Refer to OEM datasheets for specific maintenance instructions.

Visual inspection checks

• Review service books for any recorded incidence.
• Ask previous operators about any in-service or maintenance issues.
• Condition of hoses for wear, damage, scuffing, seepage.
• Evidence of external damage to components or equipment.
• Reservoir fluid levels.
• Reservoir fluid temperature.
• Evidence of fluid leaks or weeping.
• Pressure gauges reading normal.
• Filter clogging indicators at max speed/flow.
• Evidence of air breather debris/clogging.
• Cylinder rod pitting, damage, or rust.
• No unusual noises from pumps, valves, and actuators.
• Ensure surfaces, components, and drip trays are clean.

(Learn about contamination here and Hoses, filters and fitting here )

Contamination and test meters

• Fluid contamination levels if a continuous meter is fitted.
• Timing sequence changes.
• Pipework temperatures including heat exchangers.
• Visible changes or anything unusual.

(Learn about measurement and instrumentation here )

Reporting

Record all non-conformities in the maintenance record book.

Preparations

• Review service books for the last change date.
• Check new element part number and rating against original and specification.
• Check element rating against circuit or system requirements.
• Prepare tools, drip tray, and lint-free cloths.
• Prepare area against loss of fluid into the environment.

Safety checks

• Power unit or supply must be isolated and tagged out.
• System loads safely isolated or supported.
• Accumulators and pressurised tanks vented.

(Learn about the risks of fluid power at www.e4training.com/hyd_maint/fluid_risk1.php)

Filter element replacement

• Thoroughly clean the outside surfaces of all components to be worked on.
• Break the fluid siphon by cracking lines, if no check valves are present.
• Remove filter bowl and extract dirty element.
• Examine fluid quality for damage, keep sample for later comparison/analysis.
• Check filter debris for signs of contamination source or components starting to fail.
• Clean filter bowl and connections with a lint-free cloth.
• Check seals and connection threads for damage.
• Install new element and replace bowl.
• Re-open all isolators that were closed for maintenance.
• Check reservoir fluid levels.
• Restart system following the start-up procedure.
• Update service book details.

(Learn about hydraulic filters here )

Preparations

• Review service books for historical data.
• Check hose replacement dates in hose register.
• Check instrumentation is within calibration periods.
• Faimiliarise yourself with the equipment maintenance manuals and procedures.
• Faimiliarise yourself with the circuit drawing, operation, and components.
• Prepare area against loss of fluid to protect the environment.
• Prepare tools, drip tray, and lint-free cloths.
• Thoroughly clean equipment, components, and pipework.

Baseline recordings

• Start a new maintenance record sheet. Note the ambient temperature plus key parameters such as the following measurements and observations.
• Check all connections for fluid leaks, moisture, or seepage. Mark any loose connections with clear lines that show the current nut vs fitting angle.
• Measure fluid cleanliness to ISO 4406 or equivalent.
• Measure the pressure and temperature ranges under steady-state, normal, and worse case operating conditions. Ensure readings stay within the component and system design limits.
• Check the equipment is being operated within the manufacturer's specified operating limits.
• Look/listen for any unusual noises, irregularities, or operational issues.
• Compare operation, sequence, or timings with previous data.
• Check pressures levels on gauges or at every test point.
• Record electronic feedback signals or other monitoring devices.
• Measure pump, case drain, electric motor, valves, solenoids, and pipework surface temperatures looking for suspect hot spots.
• If fluid aeration is suspected or sharp, cavitation-style cracking heard around the pump then inspect the reservoir for air bubbles or fit a clear suction hose.
• Test emergency stop buttons operation and location
• Measure electric motor current in all 3 phase legs
• Write down all measurements and observations clearly.

(Learn about measurement and instrumentation.)Safety checks

• Complete/review appropriate risk assessment.
• Ensure power unit or supply is isolated and tagged out.
• Ensure system loads are safely isolated or supported.
• Check all accumulators and pressurised systems vented.

(Learn about the risks of fluid power.)Typical maintenance requirements

• Replace fluid filter elements and examine debris for traces of early component failure.
• Replace air breather filter elements and note clogging levels.
• Check and clean the strainer in the cooling water pipe (if fitted).
• Tighten all loose connections observing the fitting manufacturer instructions. Replace elastomer seal (if fitted) or with a new fitting (preferably an appropriate, modern leak-free design) if leaks persists.
• Check age (manufacture date on side) and condition of hydraulic hoses. Replace any hose with signs of wear, cracks or aging.
• Check hose guarding and/or tethering system.
• Check actuators for signs of wear. Particularly cylinder rods, seal, and pivots. Plus motor shafts and seals.
• Check flexible couplings for excessive play, wear, or signs of misalignment.
• Check accumulator pre-charge pressure.
• Check valves, solenoids, and pipe clamps, etc are secure with fixings tight.
• Readjust and reset all control valves that show inconsistencies or drift in the baseline tests. Always check the equipment maintenance manuals and component datasheets as every machine will have different set-up and operating settings.
• Check bolt torque in key areas such as pumps, electric motors, actuators, etc.
• Check limit switch actuators and mountings for tightness or damage
• Check guarding and safety barriers in place and secure.
• Check wire tightness at the terminal strip and wire routings are secure and undamaged.
• Record all maintenance observations and activities in the service book.

(Learn about hydraulic maintenance here with training exercises here. Learn about components here.)

Scheduled maintenance shall follow all of the steps listed in the periodic maintenance including the following additional actions.

• Send a fluid sample to the manufacturer or fluid testing service to check for contaminants and wear. The oil sample should be analyzed for viscosity, wear metals, particle count and the neutralization value.
• If the fluid condition is poor and needs to be replaced. Drain the power unit fluid reservoir and thoroughly clean inside the tank.
• If the fluid is to be re-used, make sure to drain and store it in clean containers.
• When re-filling the reservoir, make sure to filter the new or re-used fluid through an appropriately rated filter.
• Pumps may be changed against running hours or PQ test results. (Learn about pumps at www.e4training.com/hydraulic_pumps/)
• If operating times are slow, measure/compare case drain flow under consistent operation with ‘appropriate' flow meter or over time into a bucket.
• Check the pump and motor flexible drive couplings.
• If the servo, or high-performance proportional valves require service, notify the component manufacturer or a service engineer authorized by that manufacturer to perform maintenance.
• Check the condition of the hydraulic system by testing all hydraulically actuated components.

Final release test

• Follow the start-up procedure before restarting equipment (Learn about start-up procedures at www.e4training.com/hyd_maint/operate1.php).
• Repeat the baseline tests to ensure the machine is working within approved limits
• Record measurements and observations in maintenance record book.