1. Scope and purpose
This technical regulation establishes the procedures for scheduled and unscheduled maintenance of axial-piston, gear and plate hydraulic pumps of industrial equipment at enterprises of Ukraine. The document is designed for equipment repair mechanics, reliability engineers and shop managers.
The procedure should be carried out in accordance with the schedule of planned and preventive repairs (PPR), as well as in cases of a drop in volumetric efficiency below 80%, the appearance of uncharacteristic noise (cavitation, buzzing), an increase in the temperature of the working fluid above 65°C or leaks due to sealing. The manual applies to hydraulic systems of metal cutting machines, presses, foundry machines and mobile equipment with a working pressure of up to 350 bar.
2. Safety measures
WARNING! HIGH PRESSURE AND ENERGY HAZARD.
Before starting any work, perform a Lockout/Tagout (LOTO) procedure in accordance with the requirements of NPAOP 0.00-1.75-15 and DSTU EN 1037. Switch off the electric drive of the pump, lock out the main switch and post a warning sign. Release the residual pressure in the hydraulic system through pressure gauge lines or drain valves to 0 bar. The working fluid under high pressure can pierce the human skin, causing serious intoxication and amputations. Use a full set of PPE: safety glasses with side protection (DSTU EN 166), oil-resistant nitrile gloves, protective clothing and special shoes with metal toes (DSTU EN ISO 20345). The temperature of the pump before dismantling can reach 70°C - use heat-resistant gloves.
3. Necessary tools and materials
| The name of the tool / material | Technical specification | Quantity |
|---|
| Torque wrench | Range 10–100 Nm (error no more than ±4%) | 1 pc. |
| The torque wrench is large | The range is 50–350 Nm | 1 pc. |
| Digital multimeter | True RMS, temperature and current probe testing | 1 pc. |
| Laser thermometer (pyrometer) | Range -50°C to +500°C | 1 pc. |
| A set of socket wrenches and hexagons | Metric, sizes from 4 mm to 24 mm | 1 set |
| Lever micrometer / caliper | The range is 0–50 mm, the price of the division is 0.01 mm | 1 set |
| A set of flat probes | Thickness 0.02–1.00 mm | 1 pc. |
| Digital manometer | Accuracy class 0.6, range 0–400 bar | 2 pcs. |
| Laser shaft centering device | The measurement accuracy is 0.01 mm | 1 set |
| Container for collecting oil | Clean plastic/metal container, capacity 50 l | 2 pcs. |
| Lint-free napkins | Technical paper or fabric (cotton) | 1 pack |
| Hydraulic fluid | ISO VG 46 (or according to OEM passport) | As needed |
4. Checklist before starting maintenance
| Checkpoint | What to check | Acceptance / rejection criteria | Notes |
|---|
| 1. Visual inspection of the case | Cracks, chips, traces of corrosion, paint condition | Absence of cracks and oil leaks on connectors. Deviation: the presence of cracks - replacement of the case. | Check in bright light |
| 2. State of the working fluid | Color, transparency, presence of water and mechanical impurities | The liquid is transparent, without sediment and a sharp burnt smell. Turbidity indicates the presence of water >0.05%. | Take a sample from the bottom point of the tank |
| 3. Suction line | Integrity of hoses, tightness of clamps and flanges | Lack of air suction. Any cracks on the sleeves - immediate replacement. | Critical to prevent cavitation |
| 4. Electrical connections | Reliability of motor terminals, insulation resistance of windings | The insulation resistance is not less than 20 MΩ (megohmmeter 500 V). Screws are tightened according to the nominal value. | Check with a multimeter |
| 5. Oil level and temperature | Oil tank level, suction temperature | The level is within the mark window (75-90%). Oil temperature within +30°C...+55°C. | Measure with a pyrometer |
5. Step-by-step service procedure
Equipment preparation and shutdown
- Stop the technological cycle of the pumping station in a safe position of the actuators.
- Turn off the automatic power supply of the electric drive of the pump, install the padlock and die according to the LOTO protocol.
- Close the shut-off valve on the suction line from the hydraulic tank to the pump (if present).
- Connect the manometer to the control point of the pressure line through a quick-disconnect connection (RSHZ).
- Completely release residual pressure by slowly opening the drain valve. Typical error: failure to wait for the flywheels to come to a complete stop or residual pressure in the accumulators, which leads to oil leakage.
Dismantling and disassembling the pump
- Disconnect pressure and suction pipelines, close their openings with clean plugs to avoid contamination.
- Unscrew the fastening bolts of the flange connecting the pump to the electric motor (usually 4 M10-M16 bolts). Use a socket wrench.
- Carefully remove the pump from the seat, avoiding distortion of the shaft. The weight of the unit can be from 15 to 85 kg - use lifting mechanisms.
- Move the pump to a clean bench in the repair shop. Drain the remaining oil into a special container.
- Unscrew the bolts securing the back cover or distributor of the pump body. Fix the sequence of details. A typical mistake: disassembling a unit on a dirty machine without washing the external surfaces, which leads to the abrasive getting inside.
Measurement of wear and defecting of parts
- Wash all parts in an ultrasonic bath using a water-based cleaning solution or pure kerosene. Dry with compressed air under a pressure of no more than 3 bar.
- Measure the diameter of the shaft necks and pistons (for axial-piston machines) with a micrometer. Permissible gap in friction pairs: piston-cylinder no more than 0.015-0.025 mm.
- Check the flatness of the distribution plate with a feeler plate and indicator needle. Beating or wear should not exceed 0.01 mm.
- Inspect gear teeth (for gear pumps) for pitting, chipping, and profile wear. Measure the radial gap between the tooth and the body (norm: 0.03–0.08 mm). A typical mistake: using worn parts "until it jams", which causes an emergency destruction of the entire hydraulic system with metal shavings.
Replacement of seals and assembly
- Replace all rubber rings, shaft seals and cuffs with new ones from the original repair kit. Lubricate them with a thin layer of clean ISO VG 46 hydraulic oil before installation.
- Assemble the pump in the reverse order, controlling the ease of rotation of the shaft by hand. The shaft should rotate smoothly, without jamming.
- Tighten the cover bolts with a torque wrench in a criss-cross pattern. Tightening torque for M8 bolts — 25 Nm, for M10 — 49 Nm, for M12 — 85 Nm. A typical mistake: tightening "by eye", which causes the body to tilt and the mechanism to jam when reaching operating temperature.
Assembly and filling with working fluid
- Install the pump on the base plate of the electric motor. Align the shafts with a laser device. Permissible radial and axial displacement is no more than 0.05 mm.
- Connect the pipelines, check the reliability of tightening the threaded connections.
- Fill the internal cavity of the pump with clean hydraulic oil through the drain hole before connecting the drain line (critical for reciprocating pumps to prevent dry friction on first start).
- Open the shut-off valve on the suction from the tank. Make sure the oil flows in by gravity.
6. Post-Service Checklist
| Test | Expected result | Actual result | Passed / Failed |
|---|
| 1. Checking the direction of rotation | According to the marking on the case (clockwise or counter-clockwise) | [ ] | [ ] Passed [ ] Failed |
| 2. Idling (first 3 minutes) | Smooth noise without buzzing, no cavitation and foaming in the tank | [ ] | [ ] Passed [ ] Failed |
| 3. Pressure test without load | The pressure at idle does not exceed 5–10 bar | [ ] | [ ] Passed [ ] Failed |
| 4. Measurement of working pressure | Compliance with the nominal parameters of the hydraulic circuit (for example, 160 ± 5 bar) | [ ] | [ ] Passed [ ] Failed |
| 5. Airtightness of connections | Absence of oil leaks on flanges, seals and fittings during 15 minutes of operation | [ ] | [ ] Passed [ ] Failed |
| 6. Thermal mode | Stabilization of the temperature of the pump body and working fluid within +45°C...+60°C | [ ] | [ ] Passed [ ] Failed |
7. Troubleshooting guide
| Symptom | Probable nature / cause | Corrective action |
|---|
| Increased noise and vibration (cavitation) | Air suction on the suction, clogged suction filter, high oil viscosity | Check the tightness of the connections of the suction line, replace the filter element, warm the system up to operating temperature. |
| The pump does not create pressure | Shaft key cut off, engine rotation in reverse, safety valve stuck in open position | Dismantle the coupling and check the key, change the motor power phase, flush and adjust the relief valve. |
| Oil leakage through the shaft seal | Worn cuff, excessive pressure in the drain line (>0.5 bar), burrs on the shaft neck | Replace the stuffing box, check the capacity and diameter of the drainage pipeline, restore the shaft neck. |
| Pump overheating (over 70°C) | Internal bypass due to worn plungers/distributor, insufficient coolant flow | Diagnose the volumetric efficiency, replace a worn cassette or rocking assembly, flush the heat exchanger. |
8. Recommended maintenance schedule
| Task | Frequency | Estimated duration | Qualification level |
|---|
| Visual inspection, oil level control, temperature measurement with a pyrometer | Daily (before the start of the shift) | 10 minutes | Operator / On-duty mechanic |
| Analysis of the purity of the working fluid (purity code for ISO 4406), pressure check | Every month | 1 hour | Lubricants technician |
| Replacement of filter elements of hydraulic lines, checking of bolt tightening moments | Every 1000 hours of operation | 3 hours | Locksmith-repairman (3-4 grade) |
| Full revision service, replacement of seals, check of wear of parts | Every 4000-6000 hours (or once a year) | 8–12 hours | Repair engineer (grade 5) |
9. Directory of spare parts
| Description of the part | Typical specification | Category UNITEC |
|---|
| Seal repair kit (seals, O-rings) | FKM / NBR, resistant to mineral oils up to 100°C | Hydraulic seals |
| Replaceable suction/drain filter element | Glass fiber, fineness of filtration 10 microns (µm), Beta 10 >= 200 | Filters and filter elements |
| Pump assembly / Gear pump cassette | OEM standard for Rexroth, Vickers, Parker, Denison | Hydraulic pumps and motors |
| Distribution plate (braid) | Bronze alloy / steel with anti-friction coating | Hydraulic pump components |
| Quick disconnect connections (RSHZ) and manometers | Thread G1/4", accuracy class 1.0, glycerin filling | Control and measuring devices |
A complete range of certified components for the maintenance of industrial hydraulic systems is available in the electronic catalog: https://www.unitecd.com/e-catalog/.
10. Links
- DSTU EN ISO 4413:2014 — Hydraulics of pneumatic actuators. General rules and safety requirements for systems and their components.
- DSTU EN 1037:2018 - Machine safety. Prevention of unexpected start.
- ISO 4406:2017 - Judicial and industrial hydraulics. The method of coding the level of pollution by solid particles.
- NPAOP 0.00-1.75-15 — Rules of labor protection during loading and unloading operations and operation of lifting equipment.
