The State of California has an extensive water storage and delivery system of reservoirs, aqueducts, and pumping plants that store water and distribute it to 25 million residents. When it came to updating the annunciator card for this system, the redesign was a challenge to say the least.
First of all, the alarm system that monitors the pumps was originally designed in the 1960s. In addition, the annunciator output cards were last manufactured (but not improved) 10 years ago by a company that is now out of business. The aging electronic components in these cards were overheating and causing a high failure rate in the installations, were no longer supported, and documentation was minimal to non-existent. Turning to Vancouver, Wash.-based Stilwell Baker for answers, the California Department of Water Resources (CDWR) asked the firm to find modern equivalent components for the annunciator output cards.
After investigating the problem, Stilwell Baker recommended redesigning the cards with low power, up-to-date circuitry and components to eliminate the failure mechanisms in the original design. Although prototypes worked well in the lab with the tester provided by CDWR, the initial field trials revealed technical issues in some of the pump stations. Stilwell Baker solved these mysteries with system-level modeling simulation and testing, followed by on-site testing and circuit modifications.
“With limited documentation available, going on-site was critical,” said Darrel Baker, president and CEO of Stilwell Baker. “The alarm systems were built in different years with different parts, so on-site measurements were key to proving the solution.”
The result was a fully documented, supportable, and reliable design that eliminated the high temperature components, reduced the overall power dissipation by 24%, and reduced the hot-spot temperatures by 140°F. The new design also increased fault tolerance in the output drive stage and now includes short circuit and over-current protection. Now, even under a direct short in the system, the alarm circuit would not be damaged.
Stilwell Baker also precisely replicated the original 1960s electrical connector system. The new cards connect directly into the existing alarm system with 100% compatibility of existing systems in the field.