The Procedure for Collecting Oil Samples from Oil Immersed Transformer

During operating oil-immersed transformers, users have to take the oil sample for some different oil tests to determine different physical, chemical, and electrical characteristics of the transformer oil.

Oil plays an important role in the manufacturing and operating of oil-immersed transformers. Therefore, we should pay special attention to taking the oil sample from the equipment. Otherwise, the surrounding atmosphere is a key factor affecting on actual oil test results.

The basic procedures of taking oil from an oil-immersed transformer are given in the following points:

1. Make sure that sampling is done by well-experienced technical personnel.
2. Take at least 1 to 2 liters of oil from the oil sample valve or bottom valve (if available) depending upon the tests to be performed.
3. Avoid taking the oil sample in rainy, stormy, foggy, and snowy weather and in high atmospheric humidity because it can affect the water contaminant of the oil.
4. Use dry and clean containers preferably made of amber-colored glass or seamless stainless-steel bottles or clear glass. Besides, plastic bottles also can be used.
5. It is needed to run some of the oil from the oil sampling valve of the transformer to ensure the removal of any contaminants in the orifice of the valve.
6. It is needed to rinse the sampling bottle with some oil before topping up the bottle.
7. Fill the bottle slowly and gently up to 95% of its capacity and allow the oil to flow against the wall of the bottle to avoid any presentation of air bubbles in the oil.  And then, we carefully close the bottle.
8. Avoid any adhesive tape-like thing on the cover.
9.  The bottle must be labeled with:
   • Name of the transformer from where the sample is taken
   • Rating of the transformer
   • Serial No of the transformer
   • Installed location of the transformer
   • Other identifications of the transformer if required.
   • The temperature of the oil at the time of collection
   • Date of collection
   • Identification of the sampling point (whether it is from the top or bottom)
10.  If the oil sample is collected in a clear glass bottle, It should be kept in a dark place.