Hi all,

We have tested several used lubricant(Clavus 68, Sabroe 68, FES No. 1) from different refrigerant compressor / chillers, found out that almost all results produce very low TAN value i.e. less than 0.01. Is it the effect of the refrigerant for TAN (ASTM D664)?

Appreciate any comments.

It is normal for a "healthy" system. Abnormal values would be in the range 0,1-0,2 mgKOH/g.
(New oils usually have <0,01 mgKOH/g )

We usually report TAN to three decimal places for that very reason. The third decimal place has useful information with refrigeration lubricants.

Thanks guys for your reply.

Specifically in ASTM D664, there is a step to minus the blank solution value. What if this blank value is higher (let say 0.004 mmol) than the refrigerant sample titrated results (0.00042 mmol)? When we calculate the result {[ (Actual titration-Blank) x 56.1 )]/ weight}to get mgKOH/g, it is a negative value.

Should it be reported as 0.000 mgKOH/g or <0.001mgKOH/g or -0.0089mgKOH/g?

This message has been edited. Last edited by: amANI,