HPU Hydraulic Diagram

Purpose & scope: This guide describes routine inspection, servicing, and basic troubleshooting for a workshop hydraulic press supplied by Hydraulic Power Unit HPU-AND-001. It is intended for trained maintenance personnel and covers typical items such as oil level/condition, filters, hoses, fittings, valves, cylinder checks, and functional tests. Replace all values with site-specific data before use.

1. Safety and Lockout/Tagout (LOTO)

• Isolate energy: Switch off and lock out electrical supply to the motor starter/VFD. Verify zero voltage where applicable.
• Relieve hydraulic pressure: Actuate the press control to bleed pressure to tank (as designed). Confirm pressure gauge reads 0 bar.
• Secure the ram/tooling: Support the press platen/ram mechanically to prevent drop or drift.
• Hot surfaces & oil: Allow the unit to cool before opening the reservoir or filter housings.
• High-pressure hazard: Never check leaks with hands; use cardboard/wood and wear face protection.
• PPE (minimum): safety glasses, gloves resistant to hydraulic oil, safety footwear; add face shield for pressurized work.

2. Required tools, consumables, and spares (example)

• Clean lint-free wipes and spill kit; drip trays
• Torque wrench set; open-ended spanners; Allen keys
• Infrared thermometer (optional) for motor/pump temperature checks
• Portable pressure gauge or test kit (rated to system max pressure) for test point verification
• Hydraulic oil ISO VG 46 (or site standard), funnels with filter screen
• Replacement return filter element (per OEM part no.) and suction strainer gasket/O-ring kit
• Hose caps/plugs for contamination control
• Tagging materials: inspection tags, lockout hasp/padlock

3. Preventive maintenance schedule (example)

4. Maintenance procedures (step-by-step)

4.1 Daily / before use checks

1. Walk around the press and HPU. Look for fresh oil under the tank, manifold, valve block, cylinder, and hose routes.
2. Inspect hoses for abrasion, blistering, kinks, or exposed reinforcement. Ensure guards/clamps are in place.
3. Check the reservoir sight glass/dipstick. Top up only with the specified oil and through a clean funnel/filter.
4. Start the unit and listen for abnormal pump noise (cavitation/whine) and motor vibration.
5. Run one slow cycle with no load. Confirm pressure builds smoothly and returns to near zero at rest (as designed).
6. Verify the emergency stop and guarding interlocks (if fitted) function correctly.

4.2 Weekly housekeeping and inspection

1. Perform LOTO and relieve hydraulic pressure.
2. Wipe down the HPU exterior, especially around the tank lid, filler/breather, and filter heads to prevent contamination ingress.
3. Check that the filler/breather element is clean and seated; replace if oil-saturated or damaged.
4. Inspect visible manifold bolts and mounting hardware for looseness. Re-torque to OEM specification if available.
5. Check electrical cabinet for dust build-up and verify cooling fans/filters are clear (do not work on live panels).

4.3 Monthly functional checks (pressure, temperature, filters)

1. Perform LOTO where required for safe access; for running checks, keep clear of moving parts and use guarding.
2. Record motor casing temperature and pump noise level at steady state (e.g., after 10 minutes). Trend values over time.
3. Check return-line filter clog indicator (if fitted). If in the red zone, schedule immediate element replacement.
4. Verify system relief pressure using the installed gauge/test point: slowly build pressure to the relief setting and record the value. Do not exceed the press rating.
5. Inspect the pressure gauge for damage and confirm the lens is clear; replace unreadable gauges.

4.4 6-monthly: replace return filter element & clean suction strainer

1. LOTO and verify zero pressure. Place drip trays and absorbent pads under the filter housing.
2. Clean the area around the filter head to prevent dirt falling into the housing.
3. Remove the filter bowl/canister. Capture and dispose of oil per site environmental procedure.
4. Replace the element and all supplied seals/O-rings. Lightly oil new seals before installation.
5. Reassemble to the manufacturer’s torque recommendation (example: hand-tight plus 3/4 turn unless otherwise specified).
6. For the suction strainer: open the tank access cover (if fitted), remove the strainer, and wash with clean solvent or approved cleaner. Allow to dry fully.
7. Reinstall strainer and gaskets, close the tank, and ensure the breather is fitted.
8. Restart the HPU and check for leaks. Record date, element ID/part number, and any debris observed.

4.5 Annual service (example)

1. Review hose and seal service life. Replace any hose older than the site limit or showing degradation.
2. Inspect cylinder rod and wiper seals for scoring, pitting, or oil weep. Address root cause before replacing seals.
3. Drain and replace hydraulic oil if oil analysis indicates oxidation, high water content, or high particle count (site criteria). Clean the reservoir bottom for sludge.
4. Inspect and test electrical protection (overload, fuses, earth continuity) per electrical maintenance procedure.
5. Confirm the press reaches target force/pressure and holds without significant pressure decay (example: <10 bar drop in 60 seconds—adjust to spec).

5. Troubleshooting quick guide (example)

6. Maintenance records (copy/paste checklist)