Expert Tribology Consultancy
Loading...
Loading...
Using Flexible Aluminium Bottles for Accurate DGA
Based on IEC 60475:2022
TriboTech ApS
Purpose: Ensure oil samples remain representative for Dissolved Gas Analysis (DGA) to assess transformer health. Always wear PPE and follow site safety protocols.
Check first that the oil is not under negative pressure. If in doubt, do not open the valve. Remove the blank flange, clean the outlet with a lint-free cloth, and flush typically 2–5 L to waste in a turbulent flow. IEC 60475 requires this every time a sample is taken.
TriboTech's take
If the transformer has a stable trend from regular samples and no issues with breakdown voltage, water content or dissipation factor (DDF), this step can be omitted; the hose flush in step 1 still applies. Include it when the trend is unknown, for example at a first sample, or when one of those parameters has been an issue. Omitting it is a departure from IEC 60475. The site owner or asset manager decides.
Before opening the valve, check that the oil is not under negative pressure. Fit a new, short piece of oil-compatible tubing. Open the valve carefully and let about 1–2 L run to waste in a laminar flow until no gas bubbles remain.
Fill the bottle one-third from the bottom, with the oil still flowing, then pour it to waste.
With the tubing end at the bottom, fill in a continuous, non-turbulent flow until no gas bubbles are seen in the oil flowing out. If filling takes more than a few minutes, take a new sample.
Let about two bottle volumes overflow to waste. Meanwhile, measure the oil temperature in the flow; note how you measured it and whether fans and pumps are running. Withdraw the tubing slowly while oil still flows.
Gently squeeze the sides until the bottle is completely full, then screw the cap on tight. Do not reuse a gasket unless it is lined with aluminium foil on the oil side.
Close the valve and disconnect the tubing. Fill in the label (see Labeling below). Retighten the cap once the oil has cooled to ambient temperature.
OEM Alignment: Always follow the transformer manufacturer's instructions for taking oil samples.
Safety Protocol: Strict adherence to site-specific safety protocols and PPE requirements is mandatory and supersedes this guide.
IEC Reference: This guide is a simplified visual summary based on IEC 60475:2022 (Method of sampling insulating liquids). It is not a substitute for the full standard. Where TriboTech's take differs from the standard, the step says so.
Get the full standard: IEC 60475:2022 Publication