Electric-hydraulic Bell A-frame dredger keeps Liyutan Reservoir at depth

In Taiwan's Liyutan Reservoir, Bell Dredging recently constructed a Bell A-frame Dredger 300. The electric-hydraulic powered dredger will be deployed in the reservoir to remove sediment built up over the years, ensuring steam generating capacity and drinking water supply for the nearby city.

The reservoir has been providing green power and drinking water for Taichung, a city in western Taiwan, since 1992. "Because the dam is built in a valley and water from the mountains continuously brings in sand and sediment, the reservoir gets shallower over the years," explains Thijs van den Outenaar, sales engineer at Bell Dredging Pumps. "It affects the drinking water supply, and less water in the reservoir also means less capacity to generate power. To prevent this, the sediment that continuously accumulates in front of the dam must be removed. Initially, this was done with a dredge of another brand, but its reliability and capacity left much to be desired. So we were contacted to come up with a solution."

Dual cutting head with water jet

And that solution was found in a Bell A-frame Dredger 300. "Our installation is fed with green power from the dam via a floating high-voltage cable. A transformer on board converts the 24 KV to 690 volts, the working voltage for the electric motors on the dredger," says Thijs. "These in turn drive the hydraulics for the Bell 300 dredge pump. The pump hangs from a winch and features a double rotating cutter head to loosen sediment from the bottom of the lake. This configuration allows the pump to remain balanced at all times, even at a depth of 70 meters on a winch, as here in Taiwan. Water jet nozzles are also installed in and around the cutting heads so that the cutting heads remain clean at all times."

Booster stations

The capacity of the Bell A-frame Dredger 300 delivered is 1,800 m3 per hour in an 80:20 water-to-solids ratio. "That means we can discharge 360 m3 of sediment per hour," Thijs calculates. "The slurry is moved horizontally over a length of 2.5 kilometers and then across the dam using two booster stations, one on board and one in a 10 ft container ashore. The great thing is that we can read and even operate the dredger completely remotely. Should assistance be required, we can log in from the Netherlands, watch and troubleshoot. Our philosophy is that every excavator operator should be able to easily handle our dredgers, and that is how we have set up the cabin." That inspires confidence, it turns out. Bell is now building five examples of the Bell A-frame Dredger 250 for the government in Thailand.