Hydraulic oil is formulated from high
quality base oils and a balanced additive system that satisfies a
variety of hydraulic equipment requirements. Hydraulic oil protects
using an effective balance of metallic detergents combined with
inhibitors to control oxidation, wear, corrosion, and rust.
The hydraulic oils have multitude of applications and usage. They
increase the component life reducing downtime and are compatible with
other engine oils used in hydraulic applications. They are good in
hydraulic systems that encounter wide ambient temperatures, systems
containing gears and bearings with anti-wear properties and industries
including: agriculture, construction, trucking, mining and quarrying.
The hydraulic oil should be kept clean ensuring good filtration and
prevention of external as well as in-house impurities. The care of
hydraulic oils starts before they are used into the system. The
following points need to be kept into mind:
- The oil barrels during need to be kept horizontal to prevent
water or other contaminants from collecting.
- The gasket inside the bung should be kept wet for an effective
use as an airtight seal.
- The oil inside the barrel can get contaminated by ingress of
airborne moisture or rust formation inside the barrel wall in the
air space above the fluid. The oil from barrel needs to be
pre-filtered before it is put to use in the system.
A dominant factor which determines the service life of the oil is
degradation through oxidation. Oxidation occurs when oxygen combines
with the original hydrocarbon molecules and gives a chain reaction.
Traces (even a few parts per million) of certain metals, particularly
copper, iron, zinc, lead and water act aE catalysts and markedly
increase the rate of oxidation.
Oxidation produces soluble as well as insoluble products and these may
form sticky substances and may deposit as gum or sludge in oil passages,
various pump parts, valve spools and ports, etc. blocking them and
restricting oil flow and making the machine run sluggishly. As a result
of oxidation, the oil becomes progressively darker and gets acidic
properties which ultimately deteriorates the life of the oil.
Steps to Combat Oxidation
Anti-oxidant additives are used in hydraulic oils to combat
oxidation. Apart from this one can use other means to retard oxidation
- Installation of heat exchanger when oil temperature exceeds 60°C.
- Incorporating magnetic plugs and filters to flush out ferrous
- Keep out copper and brass tubings from the system if the pressure
rating is above 10 bar.
When magnetic plugs are used, provision should be made to
facilitate frequent cleaning of the plugs, otherwise oil surge in the
tank may dislodge the particles from the magnet and circulate them back
into the system. Incidentally, use of magnetic plug reduces load on
Change of Oil
When oil changes are effected, the system has to be thoroughly flushed
to remove the old oxidised oil; partially oxidised oil is an effective
catalyst for the oxidation of fresh oils. Flushing is done with same oil
or with flushing oil at 40°-50°C and should be continued till
the filter is seen without any trace of contaminants.