Do you start your machine on a cold morning only to hear a terrifying, metallic squeal or grinding sound from the hydraulic pump, as if someone threw a handful of screws into it? You check the reservoir, and your hydraulic oil, instead of being clear, looks like foamy cappuccino? If you ignore these symptoms, you'll soon face a very expensive pump replacement.
The phenomenon you're dealing with is most likely cavitation (or the closely related aeration). BRhydraulic experts explain why oil starts to "boil" when cold, where destructive micro-explosions inside the pump come from, and how to save the system from complete degradation.
1. What exactly is cavitation? (It's not just regular air!)
Many operators think that bubbles in the oil are simply air sucked in from the outside. Sometimes that's true (called aeration), but true cavitation is a purely physical phenomenon and much more destructive.
How does it work?
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The hydraulic pump needs to "suck" oil from the reservoir. If, for some reason, the oil cannot flow freely to the pump, enormous negative pressure (vacuum) forms on the suction side.
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According to the laws of physics, at very low pressure, liquid begins to boil even at low temperatures. The hydraulic oil literally "tears apart," creating bubbles of gas and vapor.
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These gas bubbles enter the pump, where they are suddenly subjected to powerful discharge pressure (e.g., 200 bar).
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The bubbles rapidly implode (collapse in on themselves). This is accompanied by micro-explosions, a phenomenon that generates localized shock waves and temperatures of thousands of degrees Celsius!
2. Consequences? Pump eaten from the inside
These micro-explosions act like an invisible pneumatic hammer. They strike the metal interior of the pump (gears, pistons, casing), literally tearing off microscopic particles of material.
This process is called cavitation erosion. Gears in a pump after several weeks of operation in such conditions look as if they have been gnawed by woodworms. The detached metal shavings flow further into the system, damaging distributors, locks, and cylinders, while the pump itself drastically loses efficiency and emits a characteristic, loud roar.
3. Why does the pump choke? Most common causes
Since cavitation occurs when the pump can't "breathe," we need to locate the blockage in the suction line. The most common causes include:
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Clogged suction filter: A dirty, long-overdue filter in the reservoir is the main culprit. The oil simply cannot squeeze through it.
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Too thick oil (cold start): Attempting to work at full throttle at -15°C, without pre-heating the system, is torture for the pump. The oil is as thick as honey and cannot flow fast enough to the suction section.
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Kinked or delaminated suction hose: The thick hose connecting the reservoir to the pump may look fine from the outside, but if its inner rubber layer has detached and blocked the flow, the pump will suffocate.
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Clogged reservoir breather: When the pump sucks oil from the reservoir, air must enter to replace it. If the cap with the filter is clogged with mud, a vacuum forms in the reservoir, holding the oil and preventing it from flowing to the pump.
BRhydraulic advice: If you hear a loud whine from the pump immediately after starting the machine, immediately reduce engine speed! Give the oil time to warm up and thin out (at least several to a dozen minutes in winter) before applying full load.
Summary
Foaming oil and noisy pump operation are alarms that must not be ignored. Remember, a hydraulic pump cannot "pull" oil by force – it must flow freely to it. Ensuring a clear suction line is absolutely fundamental.
Visit the BRhydraulic.eu store, where you'll find essential components to prevent cavitation. We offer a wide selection of suction filters resistant to negative pressure. Don't let your pump suffocate during operation!
