Standard Withdrawn, No replacement   Last Updated: Jan 13, 2014
ASTM D3305-94(2005)

Standard Practice for Sampling Small Gas Volume in a Transformer (Withdrawn 2014)

Significance and Use

Gases may be formed in oil-filled electrical equipment as a result of faults. The type of fault and its severity may often be inferred from the composition of the gases.

Gas samples are taken from transformer gas spaces or from gas-collector relays in order that the composition of the gas sample may be determined.

In nitrogen-blanketed transformers, the gases generated by a fault will partition between the gaseous and liquid phases. On transformers with gas-collector relays, gas in the form of bubbles may collect in a gas-collector relay and provide a means to obtain a gas sample for analysis.

Do not draw samples from an energized instrument transformer.


1.1 This practice covers the sampling of gas from a transformer gas space or from a gas-collector relay where the volume of gas available is small and will not permit the use of Practice D 2759.

1.2 This practice covers sampling, using a gas-tight syringe as the sampling apparatus and container.

1.3 If the apparatus to be sampled is found to be under a negative pressure, the apparatus pressure should be raised by the addition of nitrogen gas until a positive pressure is obtained.

This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

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