Attached is an article regarding turbine oil: http://www.practicingoilanalysis.com/article_detail.asp...edbookgroup=PowerGen
Foam ASTM D892
A turbine oil sample will often test for foam higher than turbine OEM initial suggested levels, but typically present no field foaming issues because of the position of the suction line relative to the lube oil surface, where foam accumulates. If the foam level in the turbine sump is six inches or less and does not overflow the sump or cause level-monitoring issues, then turbine oil foaming is not usually a major cause for concern, although a sudden increase in foaming may indicate a more serious problem.
Lube oil at the turbine sump surface should show at least one clear area (no bubbles) and larger breaking bubbles should be seen at this interface.
ASTM D4378-97 offers warning limits for Sequence I of the foam test of 450 ml for foaming tendency, defined as the volume of foam generated after blowing for 5 minutes at 75˚F (24˚C), and a foam stability of 10 ml, defined as the residual foam left after a 10-minute settling period. A foam stability of less than 5 ml is a good indication that foam bubbles are breaking and the turbine should not experience foam operational problems.
When addressing a foam problem, cleanliness, contamination or mechanical causes should be investigated before field defoamant readditization can be considered. Excessive readditization can result in an even greater problem with increased air entrainment. Dirt is a leading cause of foam, so ISO cleanliness should be tested as a likely cause.
Testing for foam should be conducted only when foaming presents an operational problem and for product compatibility testing.