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A hydraulic oil press holds two kinds of oil: the edible oil it presses, and the hydraulic oil in its power unit that moves the cylinder. The hydraulic oil never touches the seed, but it is a consumable like filter paper, and the wrong grade or a skipped change is one of the avoidable reasons a pump or cylinder seal fails early. This page covers which oil to use, how much, when to change it and how.
The short answer
| Item | What to do |
|---|---|
| Grade | 46# anti-wear hydraulic oil (ISO VG 46, anti-wear type) |
| First fill | About 75 kg, roughly 4½ drums of 16 L. The exact amount depends on the cylinder model. |
| Level | Always above the red line in the oil window |
| Change | Every 6 months: oil and filter together, and clean the tank |
| Never use | Soybean oil or any other edible oil |
Buying the right oil locally
The same grade is sold under different names. Any of these is the oil the manual calls 46# anti-wear hydraulic oil:
| Name on the drum | Where you will see it |
|---|---|
| 46# anti-wear hydraulic oil, L-HM 46 | China |
| ISO VG 46 AW, AW 46, HM 46 | Most international brands |
| HLP 46 (DIN 51524-2) | European and Russian-market brands |
Better oil gives the cylinder a longer life, so buy from a known brand rather than the cheapest unlabeled drum. Bulk or drummed oil are both fine.
Why edible oil must never go in
Buyers who run an oil mill sometimes top up the hydraulic tank with their own soybean or peanut oil when the hydraulic oil runs short. Edible oil is not made to work under hydraulic pressure and heat: it damages the pump and the cylinder, and a repair caused by it is not covered. If you are short of oil, stop the press until you have the right grade.
First fill
- Remove the two screws on the tank cover, lift it off and wipe out any residual oil or water with a clean cloth.
- Fill the tank to the top through the filler cap, with a funnel, before switching on. The pump must never run dry.
- Connect the hoses and the three-phase supply, then press the jog button once: the motor must turn the way the arrow on it points, clockwise. If it does not, have an electrician swap two supply phases.
- In Manual mode, put the reversing valve to Lower and run the press head all the way down. The tank level falls as oil moves into the cylinder; keep it above the red line.
- Switch the valve to Raise and bring the head back up to the marked position. While raising, the pressure gauge should stay below 10 MPa.
- Stop the machine and top the tank up until the oil is level with the filler opening. The press is then ready for work.
The full first-run sequence, including the reversing valve and the control panel, is in how to use a hydraulic oil press. Wiring and hoses are covered in the installation guide, which also has a longer installation and operation video covering the control panel and pressure release.
Changing the oil every six months
- Run the press so the oil is warm, then park the piston at the top and switch off.
- Drain the old oil completely.
- Remove the tank cover and wipe the inside of the tank clean with a clean cloth.
- Replace the oil filter.
- Refill with fresh 46# anti-wear oil of the same grade.
- Run the piston down and up a few times in Manual mode and top up as the level settles.
One press uses about 150 kg of hydraulic oil a year at two changes, plus small top-ups. Keep one full change of the same grade in stock so a change never waits for a delivery.
Daily checks
- The oil level is above the red line before you start.
- The two pressure gauges, on the pump and on the cylinder, read the same.
- No oil weeping at the hose fittings or around the ram.
- The press reaches its normal working pressure in the normal time.
If the gauges disagree, or the press is slow to build pressure, see the wear parts and maintenance schedule. Worn cylinder seals and a clogged filter are the usual causes.
When to change early
Do not wait for the six-month date if the oil:
- looks milky, which means water has got in
- has turned dark or smells burnt
- foams in the tank
- has been contaminated during a repair
Related Reads
- How to Use a Hydraulic Oil Press
- Hydraulic Oil Press Wear Parts and Maintenance Schedule
- Hydraulic Oil Press Installation Guide
- Oil Yield Dropping? A Diagnostic Checklist
FAQ
What hydraulic oil does a hydraulic oil press use?
46# anti-wear hydraulic oil, also sold as ISO VG 46 AW, HM 46 or HLP 46.
How much hydraulic oil does the press need?
About 75 kg for the first fill, roughly 4½ drums of 16 L. The exact amount depends on the cylinder model.
How often should the hydraulic oil be changed?
Every 6 months, together with the oil filter. Clean the tank at the same time.
Can I use a 32 or 68 grade instead?
Use 46, the grade the pump and seals are specified for. If your workshop is very cold or very hot, ask us before changing grade.
Can I mix brands?
Top up with the same grade, ideally the same brand. When you switch brands, do it at a full change.
Can I use edible oil in the hydraulic system?
No. It damages the pump and cylinder, and that repair is not covered.
Questions about your press or a spare-parts order? Send us the model and what you see. Contact us.
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