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DGA Oil Sampling Procedures

Use of Metal Cylinders for the Collection of Gas-

in-Oil Samples

Metal cylinders can be used effectively to collect oilsamples from transformers. To obtain a representative

sample it is necessary to use the proper samplingtechnique. 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 thesampling of transformer insulating fluids.

Hold the cylinder i n a vertical positi on at all times.

This will ensure all ai r bubbles ri se to the top and

exi t the container.

Drain the Sampling Valve

Stagnant oil from the lower drain

valve of the transformer must be

removed before the sample iscollected. Also moisture that may

be present in the depression ofthe drain valve must be removed.To achieve this, remove the plugfrom 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

ContainerAttach the cylinder's lower valve

fitting to the tubing connectedthe transformer. Attach the

cylinder's upper valve fitting to

the tubing discharging to the

waste oil container.

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 toflow through the cylinder into the

waste container. Tap the sides of

the cylinder with a tool todislodge 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 drainvalve.Shake the cylinder then listen

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and feel for signs of incomplete

filling. If not completely filled,

redo from step 1 of Open Valvesin Ordered Sequence.

Re-Assemble Tr ansformer Valve

and Plug

Disconnect the tubing and

remove the connector from thedrain valve. Replace the original

plug on the drain valve. Applypipe dope or Teflon tape on the

plug threads to insure a good seal

and to prevent rust.

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.