Oil Sampling Procedures
Use of Metal Cylinders for the Collection of Gas-in-Oil Samples
Metal cylinders can be used effectively to collect oil samples from
transformers. To obtain a representative sample it is necessary to use the
proper sampling technique. Following the procedure below will ensure that
the sample received by the laboratory is reflective of the oil in the main
tank of the transformer. Refer to ASTM D3613 for complete instructions on
the sampling of transformer insulating fluids.
Hold the cylinder in a vertical position at all times.
This will ensure all air bubbles rise to the top and exit the container.
|Drain the Sampling Valve|
|Stagnant oil from the lower drain valve of the
transformer must be removed before the sample is collected. Also
moisture that may be present in the depression of the drain valve must
be removed. To achieve this, remove the plug from the drain valve and
drain approximately one-half to one gallon of oil into an
oil-waste container. To the drain valve, attach a plug fitted with a
tubing connector and a section of clear plastic tubing.|
|Attach the Tubing to the Container
|Attach the cylinder's lower
valve fitting to the tubing connected the transformer. Attach the
cylinder's upper valve fitting to the tubing discharging to the waste
|Open Valves in Ordered Sequence
Open the valve on the transformer.|
Open the lower cylinder valve (A).
Open the upper cylinder valve (B).
Allow about 1 quart of oil to flow through the cylinder into
the waste container. Tap the sides of the cylinder with a tool to dislodge
air bubbles. Oil running though the tubing should be free of air bubbles.
|Shut Valves in Reverse Order|
Shut the upper cylinder valve (B).|
Shut the lower cylinder valve (A).
Shut the transformer drain valve.
Shake the cylinder then listen and feel for signs of
incomplete filling. If not completely filled, redo from step 1 of Open
Valves in Ordered Sequence.
|Re-Assemble Transformer Valve and Plug|
|Disconnect the tubing and remove the connector from the
drain valve. Replace the original plug on the drain valve. Apply pipe
dope or Teflon tape on the plug threads to insure a good seal and to prevent
That's it. You should now have a representative sample of the oil from
within the transformer ready to be shipped to the laboratory.
Complete the information on the sample data sheet and prepare the sample for
shipment. Be sure to write down all pertinent information on the
sample data sheet.
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