In-Plant & Mobile Hydraulic Systems
Maintenance, Repair & Safety
Why fluid power works, where it shows up, and the parts of a system.
Seven habits, clean oil, and a schedule you can post. Includes a discussion.
What fails in cylinders, pumps, motors, valves and hoses. Includes a quiz.
PPE, lockout, stored energy and the hose hazards that hurt people.
A heart pushes fluid through vessels to muscles that do the work. A hydraulic machine is built the same way, and it gets sick the same ways.
More gallons per minute means a faster cylinder stroke or a faster spinning motor.
Pressure only builds when something resists: a load, a closed valve, a restriction. A pump makes flow, not pressure.
Example: 10 GPM at 2,000 psi is about 11.7 hp of hydraulic power.
Wasted power becomes heat. That is why a restriction gets hot.
Hydraulic actuators deliver roughly an order of magnitude more power density than electric motors. That is why they own the heavy jobs.
Excavators, loaders, tractors, lifts, presses, machine tools, aircraft controls, waste haulers and water plants.
The heart. Turns engine power into flow.
Engine drives the pump. Motors turn flow into spin.
The muscle. Pressure becomes straight-line force.
The brain. Direct, limit and meter the oil.
Arteries and veins. Carry oil everywhere.
Stores, cools and cleans the oil.
What to do, and what happens when you don't.
Precision parts run on clearances of a few microns. Oil can look clean and still be wrecking a pump.
What failed?
What was the root cause?
Which habit would have caught it?
What happens when you don't.
Dirty oil, old filters, unchecked alignment and heat. Everything in Part 2, left undone.
Wrong sizing, poor routing, twisted hoses, overloaded machines and skipped procedures.
Everyone says it. Most of the time the pump is the victim, not the cause. Look upstream first.
Inlet pressure drops too low, vapor bubbles form, then implode against metal. Pitted, eroded pump parts. Sounds like marbles or gravel.
CAUSES: clogged strainer, long or kinked inlet, cold thick oil
Outside air gets sucked in and mixes with the oil. Foamy or milky fluid and a whining pump.
CAUSES: loose suction fittings, low oil level, worn shaft seal
of hose failures are attributed to external physical damage: pulling, kinking, crushing or abrasion.
Snags, impacts and pressure surges.
Rubber hardens. Heat over rating can halve life.
A ragged or angled cut prevents a proper crimp and leaves debris.
Flush out rubber and wire bits before it goes on the machine.
The wrong pressure rating bursts. Check the system's peak, not average.
Inner tube and seals must suit the oil, or they swell and soften.
Each one narrows the path. That means flow reduction, pressure drop and heat. Size them for the actual flow.
The pump whines, and the oil in the tank looks like milky foam.
A boom slowly sinks with the control in neutral.
A new hose burst at the fitting after three weeks. Its lay line spirals.
The machine runs hot and the relief valve is screaming. The pump tests fine.
Pressure doesn't care that you were only going to be a second.
Personal protective equipment is the last line of defense when everything else has failed.
Rods, pins, linkages and loads can close on hands without warning.
Make sure pressure does not remain in components before you disconnect anything.
Follow the OEM's procedure to relieve and lock out the system.
Crack fittings and bolts slowly, with your body out of the line of any spray.
Know the energy sources. Tell everyone affected.
Stop the engine or electric motor the normal way.
Lock and tag the power source. Your lock, your key.
Cycle the controls. Bleed accumulators and trapped lines.
Lower or cradle booms, rams and platforms. Use blocks or cylinder locks.
Try the controls. Check the gauges. Then start work.
Do not wait for pain or swelling. A tiny wound can hide deep damage.
Do not try to treat it yourself. Keep the injured part still.
High-pressure hydraulic fluid injection, and which fluid it was.
The safety data sheet for the fluid goes with the patient.
Hours matter: earlier treatment gives better odds of saving the tissue. Follow your company's emergency procedure.
Route hoses away from anything that swings, slides or rotates.
Clamp them to stationary components so they can't whip or chafe.
Contamination is behind most failures. Filter, change and store oil carefully.
Stay under 140°F. Heat kills oil and seals.
Grease pins, torque bolts, check couplings.
Correct size, bend radius, no twist.
Heavy equipment gets a complete overhaul every 10,000 hours.
Wear PPE. Assume every line is live until it is relieved.
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