Oil Sample Collecting Techniques

i. 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 Litre 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.

ii. Attach the Tubing to the Container

Attach the cylinder's lower Valve fitting to the tubing connected to the transformer. Attach the cylinder's upper Valve fitting to the tubing discharging to the waste oil container.

iii. 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 in to the waste container. Tap the sides of the cylinder with a tool to dislodge air bubbles. Oil running through the tubing should be free of air bubbles.

iv. 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.

v . Hold the cylinder in a vertical position at all times. This will ensure all air bubbles rise to the top and exit the container.

vi. 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 ensure a good seal and to prevent rust.

NOTES:

A. Fill in the required information on the label and attach it to the container. All relevant information should be taken from the transformer nameplate. Give reasons for sampling e.g. Routine, Buchholz trip, Prior to energizing, Completion of purification, etc

B. Collect all waste oil for regeneration.

C. Oil sampling required preferably two personnel.

D. It is vital that fingers are kept clear of items of equipment, which may come into contact with the final sample. i.e, the interior of the screw caps, the end of the P.V.C hose and inside of the filler neck of the tin

E. Do not breathe into or close to the sample whilst sampling.

F. Samples should not be taken during rainy/drizzle conditions.