Hydraulic winches in cold weather

Hydraulics depend on oil flowing freely, and cold weather works against exactly that. As the temperature falls, hydraulic oil thickens, flowing more slowly and resisting being pushed through the system, and a winch that ran smoothly in the warmth can become slow, sluggish and strained in the cold. Pushed hard before it is ready, a cold hydraulic system can be damaged. None of this means a hydraulic winch cannot work in the cold, only that the cold has to be managed, mostly through the oil and a sensible start, which is part of running a winch reliably in freezing conditions, alongside the system care our note on power pack sizing covers.

Why cold thickens the oil

Hydraulic oil, like most oils, becomes more viscous as it gets colder, meaning it flows less easily and resists movement more. In a warm system the oil flows freely and the winch responds quickly, but as the oil cools it thickens, and the pump has to work harder to push it, the flow slows, and the pressure to move it rises. At low enough temperatures the oil can become so thick that it barely flows at all until it warms up. This thickening is the root of most cold weather hydraulic trouble, because a system designed around free flowing oil struggles when the oil no longer flows freely.

What thick oil does to a winch

Thick, cold oil makes a hydraulic winch sluggish and strained. The slow flow makes the winch slow and unresponsive, the high pressure needed to push the cold oil stresses the pump, hoses and seals, and the strain falls hardest at start up, when everything is coldest. A cold system worked hard before it has warmed can suffer real damage, from a strained pump to a burst hose or a blown seal, because it is being asked to move oil that does not want to move. So the symptoms of cold, sluggishness and high pressure, are also warnings that the system needs warming before it is worked.

Choosing the right oil viscosity

The most important defence against the cold is the right oil viscosity for the temperature. Hydraulic oils come in grades, and an oil chosen for warm conditions will be too thick in the cold, while one chosen for the cold flows when it needs to. Many cold climate systems use a multigrade or a lower viscosity oil that stays fluid at low temperatures yet keeps a sound oil film when warm, so the winch works across the range it will meet. Matching the oil grade to the coldest temperature the winch will actually start and work in is the single most effective step, because the oil is where the cold bites first.

The importance of a warm up

Even with the right oil, a cold hydraulic system benefits from a gentle warm up before it is worked hard. Running the winch slowly and under light load for a while circulates the oil and lets it warm, so it thins to its working viscosity before the full load is applied. This warm up avoids the strain of pushing the heaviest loads through the coldest, thickest oil, which is when damage is most likely. It is a simple discipline, a few minutes of gentle running on a cold morning, that protects the pump, motor and seals and lets the winch reach its proper performance, and it is well worth the small wait.

Water in the oil and freezing

Cold makes water in the oil a worse problem than usual. Water that has found its way into the hydraulic oil, through condensation or a leak, can freeze in the cold, blocking small passages, fouling valves and damaging components, quite apart from the corrosion it causes year round. Keeping the oil dry, through good seals, breathers and maintenance, matters more in cold climates because frozen water is an immediate, mechanical problem, not just a slow corrosive one. This is part of the wider oil cleanliness that hydraulic systems depend on, and in the cold it is one more reason to keep water out of the oil.

Seals, hoses and cold rated parts

The cold affects more than the oil. Seals and hoses stiffen as the temperature falls, and components not rated for low temperatures can become brittle and crack, leaking oil or failing under the high pressure that cold, thick oil demands. For genuinely cold conditions, a hydraulic winch should use seals, hoses and materials rated for the low temperatures it will meet, so they stay flexible and sound rather than stiff and fragile. This is part of specifying a winch for a cold climate rather than discovering on a freezing morning that a hose or seal made for milder conditions has failed in the cold.

Specifying a winch for the cold

A hydraulic winch for a cold climate is specified for it from the start. The oil grade is chosen for the coldest temperature, the components are rated for the cold, and the operating routine includes a warm up. Heating of the reservoir or oil is sometimes added for the most severe cold, so the system starts from a workable temperature. The honest approach is to tell the maker the real lowest temperature the winch will start and work in, so the oil, the parts and the routine are matched to it, rather than fitting a temperate climate winch and hoping, which is how cold weather catches a system out, as our overview of hydraulic winches reflects. Told the real conditions in advance, a hydraulic winch copes with a hard frost as a matter of course, because the cold has been designed for rather than left to surprise it on the coldest morning of the year.

Specifying a cold weather winch with us

We specify hydraulic winches for the climate they will work in, including the oil, the parts and the routine for cold conditions. See the range in our winch catalogue, read our overview of hydraulic winches and how the power pack is matched. Tell us the coldest temperature the winch will start and work in, and we will specify the oil grade, the cold rated components and the warm up routine so the winch works reliably in the cold rather than struggling or being damaged.

Frequently asked questions

Why does cold weather affect a hydraulic winch?

Because hydraulic oil thickens as it gets colder, flowing slowly and building high pressure. This makes the winch sluggish and strains the pump, motor, hoses and seals, especially at start up when everything is coldest. A system designed around free flowing oil struggles when the oil no longer flows freely.

What oil should a hydraulic winch use in the cold?

An oil grade matched to the coldest temperature the winch will start and work in, often a multigrade or lower viscosity oil that stays fluid in the cold yet keeps a sound film when warm. Matching the oil to the real low temperature is the single most effective step, because the cold bites the oil first.

Why warm up a hydraulic winch before working it?

Running it slowly under light load circulates the oil and lets it warm to its working viscosity before the full load is applied. This avoids the strain of pushing the heaviest loads through the coldest, thickest oil, which is when a pump, hose or seal is most likely to be damaged.

Does cold harm seals and hoses?

Yes. Seals and hoses stiffen in the cold, and components not rated for low temperatures can become brittle and crack, leaking or failing under the high pressure cold oil demands. For genuinely cold conditions a winch should use seals, hoses and materials rated for the low temperatures it will meet.