WearCheck Testing Capabilities
Water - Karl Fischer Analysis (KF)
ASTM D4377/D6304
Method |  Case Study #1 | 
Water - Karl Fischer Analysis (KF)

Although gross water contamination can be seen in oil, visual examination is inadequate for detection of low levels of water in oil. Karl Fischer has been the traditional analysis method for determining the moisture content of oils. The latest version improves upon the traditional KF methods with the introduction of the oven method. This method is more accurate and less prone to interference from oil additives, and base oil properties.

Benefits
  • Detect water/moisture contamination in oil
  • Accurate from 10 – 25,000 ppm (0.001 – 25%)
  • ASTM D6304 Not prone to interference from additives/base oil
Method
The Karl Fischer water titration is applicable for systems where the presence of water at levels from, say, 100-500 ppm is of importance to know. FTIR is limited to about 500-1000 ppm presently, as is the simple “crackle” or “spatter” test, that of placing a drop of the used lube directly on a hot plate heated to approximately 325°F.

The latter is used for cursory inspection of samples where water is not critical, or is evidence of invalid sampling as opposed to actual operational problems, such as with reciprocating engines. Detection of water in those types of components usually indicates an improper [cold] sample, since water in small amounts is easily evaporated away by the sump temperature in normal operation.

As always, the inspection for water should be tempered by the fact that a homogeneous sample, with respect to water content, is almost impossible to acquire. With that in mind, water can enter the system from;

  • Damaged oil coolers, and heat exchangers
  • Faulty air breathers
  • Improperly filtered make-up oil
  • Loose or missing bolts, clamps, inspection plates and filler caps
  • Condensation

KF-2.png

Figure - At excessive levels water in oil is readily visible on visual examination. Systems that are susceptible to water contmamination levels below 0.1% (1000 ppm), such as hydraulic systems and turbines, require Karl Fischer analysis to determine the amount of water/moisture present in the fluid.

Case Study #1
Polyolefins Plant - Gearbox

Cracked Steam Pipe Causes Rainmaker

As already discussed, water is a serious contaminant when present in lubricating oil. This case study illustrates the dramatic effects that water contamination can have on a system. The unit in this case study is a very large gearbox operating in a polyolefins plant. This unit is critical, if the gearbox fails then production stops and the entire plant is essentially shut down.

KF-CS1.png

Figure - This gearbox is a critical component in a chemical manufacturing plant. The gearbox nearly failed due to serious water ingression as the result of a cracked steam pipe.

The gearbox has a capacity of close to 3,500 litres (900 gallons) of oil. Amazingly within a one month span this oil became contaminated with over 9% water. It can be difficult to accurately quantitate a water contamination level over 1% due to separation and settling of the water, and the variance the sampling process can induce as a result, never-the-less a large quantity of water was obviously ingressing into this gearbox in a very short time.

Because the plant was in a planned shutdown period, after the sample on 07-23-2001 the unit underwent a complete oil change and was investigated for obvious leaks. No leaks or sources of water entry were noted at that time. A resample was taken one week later and showed that the water level was close to 0.0%. It was assumed that this water contamination must be an anomaly and that everything had returned back to normal.

KF-CS1a.png

Figure - This graph demonstrates how the initial oil change-out removed the water contamination, the root cause was not corrected (cracked steam pipe) so the water contamination level rose back to its original critical level.

The next regularly scheduled sample on 08-23-2001 (only 3 weeks later) again showed close to 9.0% water. This time the plant was in full production, so the unit could not be shut-down to conduct an oil change. A vacuum distillation unit was hooked up to the gearbox, and the unit was monitored more closely during the next several months, but allowed to run. The vacuum distillation unit was able to keep the water level at 9.0% but could not keep up with the ingress of water. At the next planned outage the unit was again investigated, and this time a steam leak was discovered in a pipe that ran next to the unit. The leak was repaired, the oil was filtered and levels returned to normal within a few months.

KF-CS1b.png

Figure - The charts above show the effects of the water ingress. A substantial increase in apparent viscosity, but more importantly a rise in the iron level (rust), and copper and lead (corrossion).

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