Two years ago had a customer, one of the major shipping companies in the USA, who lost one of their regional shipping centers when both emergency generators failed on overheating. It was a very hot summer day, the local utility asked the facility to get off line, the facility management agreed since they had a fully (they thought) operational standby system, after 40 minutes on line at about 85% load they lost first one then the other unit, leaving them dark. The units were 9 years old, regularly maintained by the local engine dealer, including a "less than 100% load test" every year.
The root cause was cooling system corrosion and partially blocked coolant passages. So why had the system failed in light of "regular maintenance". The cooling system was marginally sized for 100% load, as most standby systems are, during regular annual load tests at a lower load, no indication of overheating was noted since the only instrumentation for the cooling system is the jacket water outlet temperature, and regular load testing was performed in the winter. A slight upward trend in the jacket water temperature was noted over the previous two years, but not considered significant and not investigated further. In a normally operating cooling system at less than full load and in ambient conditions less than maximum, the engine cooling temperature regulators are controlling the engine temperature. What happened in this case (and many others)is this "reserve margin" went away over the years, and since the load testing was not requiring full cooling system capacity the problem did not become apparent until the worst possible time.
The facility saved money on 8 load bank tests by not testing at full rated load, the cost of the outage and subsequent damage and investigation far exceeded the monies saved. Oh and the insurance company ruled that the owner had not done his due diligence by not performing the "recommended testing" and so they bailed on the end user as well.
Sorry for the long winded story, but here are some facts that may help you in your decision.
This happens way more than it should, I saw these situations happen too often, for a combination of reasons, but cost savings and the desire to do the "green thing" were at the top of the list.
A standby system is typically low cost compared to other engine driven power systems, and it's rating and support systems are sized to give you what was sold and not much more (and sometimes not even what you really needed, like in the case of ambient temperature capability).
Your standby system is typically serviced by lesser experienced technicians. I'm not saying you're not getting good service, I'm saying you're likely getting what you're paying for. Most engine dealers are competetively bidding standby generator maintenance, and sending your top tech out to do monthly inspections and annual oil changes doesn't usually happen. If it starts, runs and doesn't exhibit anything out of normal parameters, it get's called good. The only time a senior tech gets involved is during more extensive testing or if a problem is noted.
Modern engines don't like to run lightly loaded, allowing them to get to the point of "wet stacking" means you are not allowing the engine to operate where it needs to, compromising reliability and performance, including emissions.
We've mostly covered the mechanical aspects, but the electrical side of the system, the generator, controls, circuit breaker and wiring also need to be qualified regularly to assure they perform as expected when needed as well.
Liability, you can look like a hero if you save money, reduce fuel consumption and emissions, but what happens to your process if your emergency system fails to perform as required? How will your management, local regulators and your insurance carrier all view your modified maintenace procedures?
My two cents worth, hope that helps.
Mike L.
