Purification and Reclamation of Turbine Oil

One of the main reasons of failures and damages of turbine oil systems (regulating, lubricating and shaft sealing) is loss of performance properties of turbine oils. It is due to the fact that some energy facilities are at a final stage of their exploitation. Besides the existing methods of oil analysis as well as equipment for purifications of oils are out-of-date and therefore cannot boast of high efficiency.

International standard ISO 4406 recommends purifying oil to 15/12 purity class with 3-25 micron particle content for reliable operation of turbine units and its components. Neglecting this requirement causes following situations:

• accumulation of mechanical impurities in gaps and throttle sections and spool gaps leading to failures of control systems;
• penetration of solid particles into bearings leading to wearing of pads  and turbine collapse;
• rise of oil conductivity and increase or risk of electric discharge between turbine rotor and babbitt bearing.

Contamination of turbine oil with mechanical impurities and water causes following effects:

• rise of oil operating temperature;
• early mechanical wear and failure of bearings;
• unsteady regulating system;
• increase in expenses for maintenance and repairs of turbine units and their parts.

Now service time of turbine oil is two to five years but often it requires premature replacement. At the same time the experience of many companies indicates that turbine oil can be successfully exploited for more than 10 years with regular purification. It is easy to calculate financial savings.

The main reason of early replacement of turbine oil is that existing filters have metal screen with mesh size 500 and 250 micron and do not ensure the required purity of oil. As a result oil accumulates various silicate, metal particles, hard resin, fiber, transparent crystalline particles as well as aging products the size of 250-500 micron.

Potential solutions to this problem are:

• stationary filters;
• centrifuges;
• purification units using vacuum treatment for moisture and gases;
• mobile and stationary units applying zeolite and palygorskite;
• plant for complete regeneration of turbine oils.

With highly contaminated turbine oils it is reasonable to use metal screens as filtration elements with filter fineness 10-20 micron. Though this method cannot give a complete solution as even filters with mesh size 20 micron can hold these contaminants only nominally which is connected with random sizes and space orientation particles in fluid flow.

Using centrifuges does not ensure purification of turbine oil out of particles size 5 micron and less. Eventually their quantity becomes unacceptable – this reduces fluid purity and speeds up its oxidization. Also centrifuges method causes oil losses.

Zeolite can crumble and fall into dust after multiple regeneration (roasting). That is why additional fine filter needs to be installed. Besides this type of sorbent has limited dehydration properties.

Palygorskite can only be effective in purifying at certain humidity, temperature and water in turbine oil.

Despite that, Fuller’s earth has an undoubtful advantage due to its multiple applications – it cannot be used with turbine oil. Due to it’s adsorbing of inhibitor and washing salts into oil, which leads to dieseling effect of oil product. Now Fuller’s earth is mostly used for recondition of transformer oils.

Mobile filtering unit СММ-Т does not have above mentioned disadvantages. They are designed for integrated treatment of turbine oils having maximum viscosity 280 cS at 50 ºС

СММ-Т units have following advantages:

• purification of turbine oils to the required purity class by thermal vacuum method in one cycle;
• considerable extension of service life of turbine oils;
• stationary (in a container, on a frame, under tent) and mobile design (on wheels, on a trailer);
• simple in maintenance and exploitation;
• spare parts included.

Depending on task СММ-Т units are used in one of three modes:

• filtration and heating of turbine oil;
• filtration, dehydration and degassing of turbine oil;
• vacuum of an external equipment.