Symptoms

main symptom of the “Corrosive sulfur without DBDS – C2” criticality is related to the presence of corrosive sulfur compounds in the oil. In particular, the main diagnostic indicator for this criticality is:

TCS – Total Corrosive Sulfur (IEC 62697-2)

Total corrosive sulfur can be expressed as the sum of all corrosive sulfur compounds or as the concentration of DBDS equivalent.

If the TCS concentration, expressed as DBDS equivalent, exceeds the recommended values (see table in the diagnosis section), the required treatments must be performed.

There are other co-factors useful for completing the diagnostic picture:

Potentially corrosive sulfur – CCD Test (IEC 62535)
Corrosive sulfur (IEC 62535, ASTM D1275 Method B, DIN 51353)
Oil fingerprint: profile GC-AED/GC-MS (IEC 62697-1)
Additives:Passivators (BTA, Irgamet 39, Irgament 30); oxidation inhibitors (DBPC, DBP)
Total sulfur (IP 373)
Particles (IEC 60970)
Evaluate T1, T2 and T3 through dissolved gas analysis (DGA – IEC 60599)
Total acidity TAN (IEC 62021-1 or IEC 62021-2)

Oil Fingerprint. It shows the presence of sulfur compounds responsible for oil corrosivity

DBDS analysis methods are unable to determine the corrosiveness of sulfur compounds responsible for the “Corrosive sulfur without DBDS – C2” criticality.
To determine total corrosive sulfur, in particular that not due to DBDS, Sea Marconi has invented, developed, industrialised (and patented No. 0001394617 of 2008) the method called TCS – Total Corrosive Sulphur. This analytical technique is independent of individual corrosive compounds, but evaluates the effects equivalent to DBDS in terms of the amount of copper sulphide product (under the same test conditions).
This method will be included in the IEC 62697 standard, Part 2 “Test Methods for Quantitative Determination of Total Corrosive Sulphur (TCS)” currently in the Committee Draft for Voting (CDV) phase. The round robin tests performed were excellent and formed the basis for the IEC working group.

Development of this method has experimentally shown that the conversion of the different sulfur compounds into total corrosive sulfur (TCS) occurs differently depending on the temperature and the molecular characteristic of the compounds themselves.