Although Alaska is the largest state in the U.S., its population density is among the lowest. It's estimated that more than 80 percent of the towns and villages in the state's interior depend solely on diesel engine generator sets to supply electric power. And because winter temperatures in the interior can plunge to as low as -60 [degrees] F, genset reliability is obviously critical.

Along with the bone-chilling cold itself, challenges to dependable gen-set operation in winter include fuel gelling, buildup of sheet ice inside intake air flues and ductwork, severe wind and snow.

One consistent problem with generating sets operating under these conditions is thermal shock. Although a generating set and its ancillaries are typically contained within a climatized building or enclosure, the engine cooling radiator is often located on the building's roof and exposed to outdoor ambient temperatures. Consequently, when the engine's thermostat opens and sends hot coolant to the radiator, thermal shock can break the connection between the radiator core and header. Not only does this cause gen-set shutdown due to coolant leakage, but it can also contaminate the environment.

"Years ago, leaking generating set radiators were common in supplying electric power to the Alaskan bush," explained John Cameron, manager of Pacific Detroit Diesel-Allison's Anchorage, Alaska, operation. "Cooling system failures resulted from both the severe cold and less-than-desirable modes of gen-set transportation. Thermal shock in the cooling systems of stationary electric power plants caused conventional radiators to crack and fail - and always at the most inopportune times.

"There's nothing more disturbing than watching your anti-freeze solution leak into the tundra - not to mention the environmental contamination - and with the loss of a power plant, people's safety is jeopardized as well."

Further, Cameron pointed out, many conventional radiators are not field repairable. Therefore, the damaged section of the radiator must be sealed off, which compromises the radiator's cooling capacity.

Headquartered in Portland, Ore., and founded over 30 years ago, Pacific Detroit Diesel-Allison (PDDA) is the distributor for Detroit Diesel and Allison products, VarityPerkins diesel engines, Volvo Penta marine products, Kohler generator sets and Hobart ground power units.

The main focus of PDDA's Alaska branch is the prime and standby power generation, construction and marine markets serving the oilfield; utilities; remote villages and settlements in the outlying regions of Alaska; settlements in the Russian Far East; and hotels, hospitals and communications centers.

With so much of its equipment in outlying areas, the radiator thermal shock problem was a big one for PDDA. It ultimately turned to L&M Radiator's Mesabi heat exchangers with flexible core seals. The fluorocarbon rubber seals are designed to hold individual cooling tubes in the radiator headers and absorb the vibration and shock that can cause soldered seams to crack and leak. The flexible seals also allow the tubes to be removed on-site with hand tools should replacement or cleaning be necessary.

While originally engineered for larger mobile mining equipment, PDDA uses the Mesabi tube and O-ring design radiators in electric power generation units ranging from 20 through 3500 kW. Many of these units experience temperatures ranging from -60 [degrees] F to 180 [degrees] F. According to Cameron, "In Alaska today, the Mesabi radiator has become a standard by which most other engine cooling products are measured. Since 1970, PDDA Alaska has provided Mesabi radiators in all its heat recovery and cogeneration systems, including critical standby installations for major telecommunications companies, hospitals and remote villages. The radiators are also standard in our custom designed Arctic Paks."

Developed by PDDA in the late 1960s, Arctic Paks are modular, transportable gen-set packages, including engine-generator set, controls and switch-gear, day tank, jacket water heaters, space heaters, oil pan heaters, lighting, etc., all contained in an insulated enclosure designed to withstand applicable snow and wind loads.

Cameron also noted that Mesabi radiators have become standard issue in the Alaskan oil patch, where they are used by all the major oil companies operating there.

A typical example of a PDDA Alaska gen-set installation incorporating L&M Mesabi radiators to prevent thermal shock radiator damage was a turnkey installation featuring two, identical 1200 kWe diesel gen-sets supplying standby power for a major telecommunications company in Anchorage. Each package featured a skid-mounted, turbocharged and intercooled, mechanically unit injected, Detroit Diesel V16 type 16V-149TI engine driving a Marathon Electric model 744FSL4658 generator.

The engines are controlled by Woodward 2301A-9905 governors with EG2P ball head actuators. Each 1200 kW/1714 kVA (0.7 power factor, 80 [degrees]/400 rise) at 1800 rpm, continuous-duty rated, single-beating generator was wired for 480 V, three-phase, 60 Hz service and included Class H insulation and Basler voltage regulation equipment.