Acid number of transformer oil is one of the most important parameters of this oil product. The determination of the acid number is an integral part of both the abbreviated and full analysis of transformer oil.
In general, the acid number is the number of milligrams of KOH required to neutralize 1 g of oil.
This parameter is also to be determined during acceptance tests. This requires boiling ethyl alcohol, through which all free acids are extracted from the oil. Then they are titrated with an alcohol solution of potassium hydroxide with an indicator.
In the case of mass tests, if an acid number exceeds its own norm, a simpler method using an alcohol-benzene mixture is used.
It can be said that the acid number is a characteristic of the degree of removal of naphthenic acids from the oil, which under certain conditions can provoke corrosion of metal surfaces.
When acids interact with metals, salts are formed, which reduce the resistance of oils to oxidation, increase its emulsifiability with water, and also have a negative effect on dielectric strength.
As we answered above, the acid number is a normalized parameter and if the recommended value is exceeded, measures should be taken to reduce its numerical value.
For removal from the transformer acid components and decomposition products, it is advisable to use the installation type transformer oil recycling CMM-R of the brand GlobeCore. This equipment is designed specifically to extend the service life of power transformers by restoring the chemical composition and dielectric strength of insulating oils.
The undoubted advantage of the CMM-R units is the possibility of carrying out the regeneration of oils directly in the transformer, which can remain both under voltage and without it.
Oil treatment at the place of operation allows the residue to be dissolved from the winding insulation and removed with the help of Fuller’s sorbent earth.
The sorbent itself can be used many times due to reactivation directly in the regeneration equipment. The process is not interrupted by the search and replacement of the absorbing substance, which reduces the regeneration in time.