THE MYSTERY
A manufacturer of aircraft parts was having mystifying issues with their Turco tank. Sometimes the customer could turn on the machine and the burner with no problem — but then 10 minutes later it would randomly shut down and sound an alarm. At other times they couldn’t even start it at all.
This was a tank full of cleaning solvent that had to operate at a very specific temperature and was critical to the customer’s manufacturing process. They needed it up and running stat so they called ACES.
THE CLUES
The first thing the ACES Control System Investigator (CSI) did when he arrived at the scene was review the machine’s drawings. Since an alarm was being triggered he knew that something was wrong on the safety circuit, which includes things like level sensors on the tanks, a UV scanner on the flame relay, the gas valves and other airflow switches. If any one of those is out it takes the whole system down.
30’ from the tank the CSI discovered an auxiliary control panel. He isolated the problem to this panel, which controlled the combustion blower. He discovered that the contactor controlling the combustion blower motor was burned out. It would have been easy to make an assumption that that was the problem, but the CSI continued to pursue this line of investigation.
THE PERP
The CSI ascertained that the motor on the combustion blower was also burned out; this was tricky to analyze, because the motor would run for awhile but then, as it heated up, something inside would give out so he had to catch it just as it was letting go.
Since a combustion blower creates a forced-air environment in the furnace, there’s a risk of flame backing up if pressure is cut off, and this makes it part of the safety circuit. This is why the faulty combustion blower motor set off alarms and brought the entire machine to a halt.
THE SOLUTION
The CSI ordered a new motor, contactor, and motor overload and the customer installed the new parts themselves. Now the Turco tank is back in action, dunking aircraft parts at an optimal and consistent temperature. And the unpredictable alarm is finally silent.