When a sample bottle is sealed with even a few millilitres of trapped air, dissolved gases redistribute between the oil and the headspace until they reach thermodynamic equilibrium. The fraction that ends up in oil is governed by the Ostwald solubility coefficient and the volumes of the two phases — and the loss is selective, not uniform.
This tool implements the partition equation directly. Sample Volume is the total bottle capacity; the headspace VG is a sub-volume of it, and VL = Sample − VG is the oil that remains. Adjust the controls below to see how much of each gas the lab actually sees at equilibrium, and where the diagnostic damage starts to show.
IEC 60567:2023 Table A.1 publishes one natural-ester column — it does not separate rapeseed, soybean and high-oleic sunflower.
|Δ| > 5 % — fingerprint will shift across zone lines
kO values from IEC 60567:2023 Annex A Table A.1
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kO values for the nine fault gases are taken from IEC 60567:2023 Annex A Table A.1, which publishes a separate column for mineral oils, natural esters, synthetic esters and silicone oils — the four families the fluid selector offers. Natural esters are one column in the standard: it does not separate rapeseed, soybean and high-oleic sunflower. The table's own caveat applies: the values are means measured on the oils of 2006, and more recent oils can differ significantly. The partition equation follows the mass-conservation derivation in ASTM D3612-02 (Reapproved 2026), §27.1, equations (14)–(17); the equivalent back-correction form is given in IEC 60567:2023, Annex D.
IEC and IEEE do not publish the same coefficients. IEEE C57.104-2019 Table G.1 (printed p. 86) gives its own Ostwald set for mineral oil, normalised to a density of 0.880 at STP, while IEC 60567:2023 Table A.1 (printed p. 53) gives means measured across several oils. Dividing one table by the other gas by gas gives ratios from 1.21 to 1.42, a mean of about 1.29 — so the IEC coefficients run about 30 % higher throughout. That ratio is not a figure either standard prints: it is TriboTech’s derivation from the two published tables (IEC 60567:2023 Table A.1 ÷ IEEE C57.104-2019 Table G.1). The calculator uses the IEC set. If you are reconciling against a laboratory that works to the IEEE table, expect the difference — and note that it is not a pure density effect, since the two tables are normalised differently.
Continue to the multi-gas Duval drift tool to see how a real fault fingerprint shifts across Triangle 1 and Pentagon Unified zones when multiple gases partition together, or to the DGA plausibility screen, which uses the same IEC 60567 solubility data to check whether a reported gas total is physically possible at all.
The tools are calculation tools made available free of charge by TriboTech ApS as part of the professional communication of its engineering consultancy. The tools perform a calculation based on the values entered and the published methods identified. They do not constitute an examination of an asset, a diagnosis, or advice on any specific asset. The tools have no knowledge of the asset's design, history, loading or operating conditions, and a result cannot therefore serve on its own as the basis for a technical or operational decision. A result is an indication, not a diagnosis. Use of the tools does not create a client relationship and does not create an advisory relationship. TriboTech ApS provides advisory services only under a concluded framework agreement, and no advisory liability is assumed for the use of results from the tools outside such an agreement. Any decision taken on the basis of a result — including a decision not to act — is taken by the user on the user's own professional judgement and at the user's own risk. As CIGRE itself puts it: "Actual actions on the equipment are the sole responsibility of engineers in charge of the transformers" (CIGRE Technical Brochure 771, 2019, section C.8, printed page 54). Each tool states which published methods and which editions the calculation is based on. The standard itself is the authoritative source, and a standard may have been revised since the edition a tool uses.
Method implementation — The calculation behind this tool is versioned. When a correction changes the result the tool gives for the same input, the version below changes with it. Version 1.1 · 27-09-2026. What changed, and when
