Thermal

The thermal energy in a fluid is increased by mechanical losses or an external heat sorce (warm surroundings or a heating element). The thermal energy level is expressed in terms of the oil temperature.

In normal practice, the oil temperature in a well functioning system will be about 40°C, with a maximum variation of 20°C. Raising the oil temperature to above 80°C would lead to a sharp drop in the usefull life of the oil.

High temperatures
A temperature above the maximum permitted operating temperature can produce the following chain reaction:
the fluid viscosity drops sharply, lubrication changes from hydrodynamic to mixed (with mechanical contact between the surfaces), wear increases and clearance between moving parts becomes greater, internal lekage increases sharply, the mechanical efficiency of the installation decreases, fluid temperature rises yet more, seals become inoperative and the fluid undergoes chemical decomposition.

The greatest danger of high fluid temperatures is breakdown of the fluid, with formation of slimes, resinous products and acids which can cause components to seize up and attack internal surfaces. And a high temperature speeds up the oxidation of oil and thus sharply decreases the life of the oil.

Low temperature
Low temperatures can cause problems too. Temperatures below 10°C (and certainly polar temperatures) can have the following advers effects:
increase in viscosity and mechanical losses, cavitation effects in the pump, leading to increased noise production or premature pump breakdown, deformation of seals, low respons rate of valves, high pressure losses in filters, causing bypass valves to open or filter elements to rupture and blockages and surface attacks due to ice particles.

Raising the temperature of the oil can be done safely with a heater but only when the heating is effected by a ‘flow-through‘ principle, preventing ‘burning’ or thermal overloading of the oil.

Need a safe way to keep your oil at a minimum temperature? Then have a look at our “heated units“.
For more information please call + 31 180 62 13 13 or contact us.