Page 59 - CARILEC CE Industry Journal_Oct_2019

CASE STUDIES However, when reviewing the combustion or engine report
(Fig. 23) for this test date, it is clear that Cylinder 1 Peak
Case Study #1-Broken Component Firing Pressure is quite low. However, the Exhaust
temperature is on the high side. The only parameter
In this case study from a high speed, 2-stroke engine that visible to Operations is exhaust temperatures and,
is an Emergency Diesel Generator (EDG) at a nuclear although indicated as “HI”, these values are within the
power plant, the data is taken during a regularly scheduled allowable range per the operating specification. It should
surveillance test. There was not any concern or awareness also be noted that, although the STDDEV (Standard
of any problem with the engine. Basic engine parameters Deviation) is the lowest, this would be attributable to the
were available to the control room staff (temperatures, low firing pressure. Also note the PFP or Peak Angle is
speed, load, etc.). Cylinder Pressures and Phased earliest as indicated here at 5 Degrees after TDC. In
Vibration data were collected as part of normal plant reality, the cylinder is firing late and low as shown in
procedures during this test. Figure 24.

Fig. 23 - Engine Combustion Report

Examining the PT Signature for Cylinder 1 (Fig. 24), it is firing pressure would normally produce a low exhaust
obvious that there is an abnormal “peak”. The peak temperature, however, because it is late (relative to
pressure is very low and late. This is likely caused by a crank-angle), it causes the temperature reading to
fuel injection or delivery issue. Interestingly, the low peak increase, masking the problem entirely.

Fig. 24 - Cylinder 1 PT Curve Fig. 25 - All Cylinder PT Curves Stacked
In Figure 25, all of the median PT Curves are stacked on top of each other which makes it very easy to see an abnormal cylinder.

CE INDUSTRY Journal 57