By Barry O’Leary
Technical Support Specialist
Caterpillar Forest Products
You can experience fewer repairs to pumps and motors with some simple preventive maintenance. You’ll achieve the biggest impact by focusing your efforts in four areas.
Hydraulic Oil—Always use high quality hydraulic oil of the proper viscosity range that meets or exceeds the manufacturer’s specifications to ensure that it contains the following properties:
- Anti-wear agents should contain a minimum 900 parts per million (ppm) of zinc.
- Emulsifiers disperse small amounts of water in the oil to minimize component damage.
- Defoamers and air release agents prevent formation of bubbles by reducing oil surface tension.
- Anti-oxidants prevent high-temperature formation of sludge and corrosive acids.
- Detergents/dispersants keep components free of deposits and break up contaminants.
- Operator Technique—A conscientious operator can help control repairs by practicing good habits.
- Daily walkaround: Check the hydraulic tank level and check wiper seals and hoses for leaks to reduce the chance of contaminant entry.
- Cold starts: Exercise the hydraulic system for five minutes at low RPM when ambient temperatures are cold.
Contamination Control—Depending on the type of contaminant, you can experience the following problems:
- Abrasive particles like aluminum and silica cause sticky valves and poor pump performance.
- Water in hydraulic fluid forms bubbles that pit internal component surfaces.
- Air in the system causes jerky motion.
- Heat reduces the lubricity of hydraulic fluid, accelerating component wear.
To avoid these problems, operating hydraulic system cleanliness levels should be ISO 18/15 or better. Watch out for these contaminant sources:
- Exposure to external environment via worn seals, faulty gaskets, leaky valves or defects in cylinder rods.
- Internal wear due to insufficient lubrication or improper clearances.
- Installing new components, like hoses, that are dirty.
- Adding fluids that were stored in dirty containers.
Maintenance—Diligence and dedication are key to keeping problems in check:
- Use proper filters and change them regularly. Use high efficiency filters after any repair for a maximum of 250 hours; then resume use of standard filters.
- Use proper hydraulic fluid, filtering it when transferred between storage locations.
- Remove contaminants from a dirty system with kidney loop mobile filtration or flush a dirty system and fill it with new fluid.
- Fluid sampling: A regularly scheduled fluid sampling program—every 500 hours in most applications—will monitor component wear and oil condition, detecting increases in contaminants early. Fluid sampling determines the wear rate of internal components, so you can make repairs or replace components before failure.
- Particle count: Wear-rate analysis only tells you about the type of contaminant. Particle count will show quantity and size of the debris, and whether it is metal, rubber or synthetic.