Generator sets keep Andean gold and silver flowing

The Peruvian Andes are the world’s highest mountains outside of Asia. They also were the source of much of the gold and silver for which the Incan empire was so famous. The Inca are gone, but the mountains of Peru are still a rich source of precious metals. Today, however, it’s extracted by sophisticated mining technology powered by electricity and diesel engines rather than human muscle.

The new Inmaculada mine is the latest chapter in the centuries-old quest of Andean gold and silver. It’s located on 20,000 hectares (49,421 acres) approximately 210 kilometers southwest of Cuzco and 530 kilometers southeast of Lima at an altitude ranging from 4,500 to 5,400 meters (14,763 to 17,716 feet). Owned and controlled by Hochschild Mining plc, the property consists of 40 mining concessions which will produce and estimated 124,000 ounces of gold and 4.2 million ounces of silver annually at full production.

A major feature of the site is the 5,000 ton per day gold concentrator plant built by Grupo Graña y Montero (GyM) headquartered in Lima. GyM also did extensive earthwork and other construction at the site to support mining and logistical requirements. All of that construction activity required a lot of electric power, about 2.2 mW at the peak of operations, and all of it had to be generated on-site due to the remoteness of the installation.

"We also had to find technicians who could pass the rigorous medical examination necessary to work safely at that altitude. Even those who pass have to be rotated out on a regular schedule to allow them time to rest and recuperate at lower altitude.”

In all, Modasa supplied a total of 13 Perkins powered generators to handle peak requirements at Inmaculada, five of which are permanently installed to provide 0.4 mW of power 24/7 at the mine. 

The generator sets powered by Perkins 404, 1104 and 1106 engines were equipped with special preheating glow plugs and 2,000 watt cooling water heaters to ensure reliable starting at low temperatures. The larger 1306 and 2206 engines were equipped with 4,000 watt heaters to handle the larger volume of cooling water in their systems.

“We had to make a few modifications to the generator sets,” Schroeder said. “The motors on the water heaters had to be changed and the control electronics and starter voltages had to be adjusted to compensate for the altitude and temperature. But, other than those minor adjustments the Perkins engines met everyone’s expectations for trouble-free performance.”

Modasa is a turnkey supplier to the Inmaculada mine, providing on-site maintenance personnel, spare parts, consumables and emergency services. Their personnel are on-site for 20 days of each month and are then rotated out for 10 days of low altitude rest and recuperation.

The engines are serviced on a regular schedule every 250 hours because of the rigorous operating environment. They are always in operation except for a 20 minute routine service.

“We have needed to change fuel filters more often than we normally would,” Schroeder noted, “because the fuel tends to become contaminated during transport to the remote location. And, we use a special SAE 15/40 engine oil in these units. With that care, though, they have been absolutely reliable for the 6,000 hours of continuous use they have see this far.

“In fact,” he added, “one of the MP 350 generator sets used at Inmaculada was actually requested by another customer who was aware of its reliable performance at the site. They rented it immediately upon its return to Lima and ran it 24/7 for the next three months at their site.

“All told, by the time it came back to us it had been in operation for seven months in the high Andes without any unscheduled downtime. Perkins engines are tough. That’s why we use them.”