Cem Özdemir
For many factories in Bangladesh, from ready-made garment units to food processing and pharmaceuticals, the diesel generator is not an emergency machine. During periods of load shedding and gas supply constraints, it may run several hours every day. At that level of use, diesel becomes one of the largest operating costs of the plant. Reducing it does not always require new equipment. In many factories, the biggest savings come from how the existing sets are loaded, maintained and managed.
Understand how a diesel engine uses fuel
A diesel generator is most efficient when it runs between roughly 60 and 85 percent of its rated load. At very low load, fuel consumption per kWh rises sharply, because the engine still needs fuel to overcome its own friction and run its fan and pumps. A set that produces 100 kWh at 25 percent load may use considerably more fuel than the same set producing 100 kWh at 75 percent load.
Low load also harms the engine. Incomplete combustion leads to carbon deposits, unburnt fuel in the exhaust system, a condition called wet stacking, and oil dilution. Over time this raises maintenance costs and reduces reliability.
Match running capacity to the actual load
Many factories install one large generator sized for full production, then run it for hours at partial load during lunch breaks, night shifts or when only some lines are working. Where several sets are available, a paralleling system with automatic load-dependent start and stop allows the plant to run only as many sets as are needed. Even without automatic paralleling, a simple operating procedure that selects a smaller set for light-load periods can save significant fuel.
When adding new capacity, it is often better to add a second set that can be paralleled with the first rather than replacing it with a single larger unit. This also provides redundancy.
Measure before you manage
Fuel savings cannot be managed without measurement. A basic system records running hours, kWh produced and liters consumed for each set, so that specific fuel consumption, in liters per kWh, can be tracked. A sudden increase in this figure is often the first sign of an engine problem, a clogged air filter, injector wear or fuel losses. Remote monitoring makes this tracking much easier and also helps detect fuel theft, which is a real cost for many plants.
Power factor and motor loads
Garment and textile factories have many motors, from sewing machines to compressors and fans. A low power factor increases the current the alternator must supply. While the engine's fuel consumption depends mainly on kW, a poor power factor can force the plant to run more sets or a larger set than the real kW demand requires. Power factor correction on the factory side, carefully designed to avoid leading power factor when on generator, can free capacity and reduce the number of sets in operation.
Cem Özdemir, General Manager, Terex Diesel
