Taking Oil Sample From Power Transformers
Dissolved gases ASTM D 3612, (IEC
60567), Dissolved water
ASTM D 1533, (IEC
The following is one of the procedures to collect transformer
Before Taking Sample:
- Transformer oil reservoir must be under positive pressure.
- All connection areas between the transformer side and the
glass syringe, including the drain valve, must be super clean.
- Use the transformers' main drain valve for oil collection
for the best results.
- Flush approximately 2 to 3 liters of oil before taking the
- Adjust the valve for the smooth flow of oil through the
tubing, to minimize air bubbles.
Taking Sample with
- Make sure that the
stopcock is securely tightened on the
glass syringe luer lock before taking the sample.
- Connect the
glass syringe to the
tygon tubing with the luer lock connector, while the side port
of the nylon stopcock is open; this allow the flushing of oil
(The handle of the nylon stopcock has off position printing with an
arrow indicating the closed port, while the other two open).
- Slowly turn the stopcock handle toward the side port to open the
syringe port; this will fill the glass syringe with oil 30- 50 cc
(mL). Quickly close the front port by moving the nylon stopcock
handle toward the tygon tube (or the transformer side) and position
the glass syringe in the vertical position.
- While the glass syringe is in vertical position and the front
port is in off position (or the nylon stopcock handle is facing the
transformer side), empty the oil and purge any air bubbles until all
of the oil has been cleared from the syringe.
- Turn the nylon stopcock handle toward the side port (or the
flushing port) and repeat this flushing procedure 2 to 3 more times
before taking the final sample.
- To take the final sample, slowly close the side port (or move
the nylon stopcock handle toward the flushing port) and allow the
transformer reservoir pressure to push the glass syringe piston
until the glass syringe is filled up to 40 cc/ml mark. Do not pull
the glass syringe piston manually because it will result in air
- 50-cc syringes should be filled up to approximately the 40-cc
- 30-cc syringes should be filled up to approximately the 25-cc
Turn the nylon stopcock handle to off position (or toward the
glass syringe) and separate the glass syringe from the tygon tubing;
inspect for air bubbles. If you detect any air bubbles, discharge
the air quickly while the glass syringe is in vertical position. To
close the syringe, turn the nylon stopcock handle to off position
(or toward the glass syringe). If there are more than a few air
bubbles, empty the syringe and repeat the process until a proper
sample has been taken. The final sample should contain no air. The
syringe should be packaged in a carrying case as soon as possible in
order to protect it from light.
- Few bubbles may form after taking the final sampling.
- Please do not try to remove the air bubbles, because they are
part of the final sample.
To purchase Glass Syringes, Nylon Valves, or Syringe Carrying
Cases, please visit our website at:
DGA SAMPLING KIT
This article is intended for preliminary information and prepration only and it should
not be used for actual sample taking. Furthermore, The Transformer Oil
sampling must be conducted by a qualified and well trained field
technician who is familiar with the electrical power equipment. To
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