Case Analysis And Explanation

Causes of hydraulic oil blackening.

1.Impact of metal impurities
* The most possible cause is the grinding debris generated by the fast rotation of the pump. The wear at all parts of pump rotation shall be taken into account, such as bearing and volumetric chamber.
* The hydraulic valve element runs back and forth, and the oil cylinder runs back and forth to generate the grinding debris, but this phenomenon does not occur for a short time;
* For the new equipment, when the equipment is running in, a lot of iron filings will be generated. Do you fully empty the hydraulic oil in the oil tank during oil change and add new oil after the oil tank is fully cleaned with the cotton cloth? If not, there may be a lot of iron filings left in the fuel tank, which will also cause the new oil to be polluted and blackened.

2.Impact of external environment
Check if your hydraulic system is closed and the breathing holes are intact; check the exposed parts of the hydraulic part of the equipment to see if the seal is intact, such as the dust ring of the oil cylinder.
* The hydraulic oil is not changed thoroughly;
* The oil seal is aged;
* The poor working environment of excavator causes the blockage of filter element;
* The air enters the hydraulic pump to cause a large amount of air bubbles;
* The hydraulic oil tank is connected to the air. The dust and impurities in the air will enter the oil tank when it is used for a long time. The oil will definitely be dirty.
* If the oil is tested for particle size in accordance with cleanliness requirements. The dust pollution can be eliminated. It is definitely caused by high hydraulic oil temperature! In this case, high-quality hydraulic oil shall be used, and the oil return filter element, cooling oil circuit, particularly, the radiator of hydraulic oil shall be inspected. The maintenance shall be carried out according to the provisions at ordinary times.

3.Causes of hydraulic oil blackening due to damaged hammer
The black hydraulic oil due to the damaged hammer is not only caused by dust, but also by the added non-conforming grease.
For example, when the distance between the bushing and the steel brazing is more than 8 mm (the little finger can be inserted), it is recommended to change the bushing. On average, one inner casing needs to be replaced for every two outer casings. When the hydraulic fittings such as oil pipe, steel pipe and oil return filter are replaced, the dust or debris at the connection of damaged hammer shall be cleaned.
When adding grease, you need to lift the broken hammer and press the steel brazing into the piston. You only need to add half of the standard grease gun for each filling. (If the steel brazing is not pressed tightly during the grease filling, the filled grease will be placed at the upper limit of the steel brazing groove. When the steel brazing is working, the grease will be directly expelled to the main oil seal of the damaged hammer. As the piston reciprocates, the grease will be brought into the cylinder of damaged hammer, and then is mixed into the hydraulic system of the excavator along with the hydraulic oil in the cylinder of damaged hammer. Consequently, the hydraulic oil is deteriorated and blackened.)

Handling methods:
1. Fill the grease correctly.
2. Install the return oil filter device.
3. Install the water spray device to reduce external dust.
4. The upper and lower bushings are worn too much and the bushing shall be replaced where appropriate.
5. The one-way valve shall be checked regularly if the intake one-way valve is broken or blocked.