Dear all,
I need your help to interpret the results of a Foam Test ASTM D892. We detected foaming in the exciter bearings (its is visible in the sight glass). This was detected after a turbine trip due to high vibration in one of those bearings, however, we don’t know if the foaming started before or after the trip. I decided to immediately do an oil analysis for particles count, water content, viscosity etc and for this time (we normally don’t do this test) a foam test ASTM D892. The analysis results were:
Oil: Super Turbo Flow 32 (ISO 32) Petrocanada Turbine Oil.
ISO Cleanliness: 17/15/11 >4μ = 1016, >6μ = 200
Water KF PPM: 26
Wear Metals: Fe = 0 PPM, Ni = 0 PPM, Al = 0 PPM. Cu = 2 PPM
Contaminant Metals: Si = 0 PPM
Additive Metals: Zinc = 1 PPM, Phosphorous = 88 PPM
Viscosity at 40 oC: 35 CS
TAN: 0.03
Foam test ASTM D892
I (5 min blowing) 260 mL
I (after 10 min settling period) 0 mL
II (5 min blowing) 30 mL
II (after 10 min settling period) 0 mL
III (5 min blowing) 50 mL
III (after 10 min settling period) 0 mL
I was very happy to see the good numbers for particles, viscosity, water content etc. Since all of them would indicate that the foaming problem is not the oil but mechanical issues in the turbine bearings or lube system. However, in the case of the Foam test I am not so sure. The fact that after each settling period the foam count was zero is very positive but I did not expect to see such high value of foam forming in the first sequence (260 mL). I called the lab and to my big surprise and disappointment they look to be as clueless as my self about whether the 260 mL was too high or not. Under pressure they finally accepted to do some research and came back to me with an answer. I paste their answer below.
The outsource lab called me back with the reruns results they are still within the test’s repeatability. According to ASTM D 6224-09 Table 3 Warning Levels of In Service Oil Test. Foaming characteristics, Tendency >450 are a fail and <450 are a pass. As a testing Laboratory we recommend that you contact your Lubricate Distributor to address the oil’s forming characteristics. Please let me know if you have any questions.
Could you offer me some advice on this topic? Can I trust my lab advice? I am thinking in the possibility of changing the lab we use.
Thanks in advance for your help.