Short answer
Running a breaker straight to full load in cold weather takes three risks at once: the oil has thickened and passes narrow galleries with difficulty, the grease has lost its flow and does not reach the bushing, and because nitrogen pressure falls with temperature the breaker behaves differently from expected. The answer to all three is the same and it is simple: a warm-up round. Running machine and attachment for a while without load returns the few minutes it costs directly as component life. A cold start does not do damage on the first day; it does damage when it is repeated.
Three things change at once in the cold
The first is hydraulic oil viscosity. Cold oil thickens and struggles through narrow passages. That means the pump works harder and the system sees higher pressure; this is the moment seals are most strained.
The second is grease. Grease stiffens in the cold and, even when pumped at the nipple, does not easily reach inside the bushing. A cold morning greasing can be a greasing that was given but never arrived.
The third is nitrogen. Pressure in the gas chamber follows temperature and falls in the cold. So a cold breaker can hit weaker than expected in its first minutes, and that gets read as weak blow and leads to a needless recharge.
The warm-up round
- 1
Warm the machine first
Before going to the attachment, follow the machine’s own warm-up procedure. Loading an attachment before the hydraulic oil is near working temperature puts that load straight onto the seals.
- 2
Move boom and arm unloaded
Circulate oil through all the lines. Simply idling the engine does not send oil down the attachment circuit.
- 3
Run the breaker briefly off load
Run it for a few short periods without setting the tool into material. Do not extend this; running off load warms it, but if it becomes blank firing it does damage.
- 4
Then grease
Grease after the warm-up, not before. Warm grease flows and reaches the bushing; grease pumped cold can stay in the passage.
- 5
Start the day on softer material
Where possible, do not begin the day on the hardest material. The first breaks load the system gradually and the breaker’s own body warms too.
- 6
Do not judge sound and power in the first minutes
A cold breaker hitting weakly at first is normal. Assess performance once it has warmed; an early verdict calls out service for nothing.
Frozen ground is a separate subject
Cold weather starting and breaking frozen ground are different things. The first is about the equipment, the second about the material.
Frozen ground is far harder than the same ground unfrozen and behaves towards a breaker like hard rock. But it is layered: past the frost depth the material beneath is soft. So breaking frozen ground aims at cracking the layer and getting beneath it, not at fragmenting a mass.
The practical consequence: on frozen ground there is even less point in staying on one spot. Progress comes the moment the layer cracks; if it does not come, move the spot.
Do not measure nitrogen pressure cold
Pressure in the gas chamber changes with temperature; measured on a cold breaker it reads low and leads to a needless recharge. Measurement is taken once the breaker is at working temperature. The correct value and the conditions for measuring it vary by model and are given in the manual.
Do and don’t
Do
- Warm the machine by its own procedure, then move to the attachment.
- Move boom and arm unloaded to circulate oil through the lines.
- Leave greasing until after the warm-up.
- Where possible, do not open the day on the hardest material.
- Have nitrogen measured once the breaker has warmed.
Don't
- Do not put a cold breaker straight to full load.
- Do not let the warm-up turn into blank firing; running off load is kept short.
- Do not mistake a weak cold morning blow for a fault and call service.
- Do not stay on one spot in frozen ground.
- Do not carry on with the same greasing interval in low temperatures without checking the grease; if it is not arriving, the interval has lost its meaning.
Grease type and cold
How a grease behaves in the cold comes from its base oil and thickener. A grease built for high temperature can lose more of its flow at low temperature; the grease that is right for summer may struggle in winter.
We do not give a numerical limit here, because the figure is in the grease’s own technical data sheet and varies by brand. The right question is: does the working temperature range of the grease you use cover your site’s winter?
We covered the difference between breaker grease and general purpose grease in its own guide; cold performance is one of the places that difference becomes visible.
What HKM uses
SolidLube grease cartridges: the temperature range is published
The cartridges we use are specified to work between -20°C and +1100°C, at NLGI 2 consistency with roughly 15 percent solid additive and a dropping point of 250°C. Those are the product’s own technical figures; you can compare your own site’s winter against that range.
Grease cartridge technical data(solid-lube.com)