There are many myths related to the calculation of the running costs of can washers, says Joe Bohlen, vice president of two-piece can technology at Cincinnati Industrial Machinery.
The items that contribute most to running costs are treatment chemicals (35 percent), electricity (27), natural gas for heating the washer’s water (15) and natural gas for heating the dryer (13).
Bohlen says there are complex variables involved in estimating the cost of ownership, which varies widely from region to region, in addition to the cost of the wear parts.
In some regions, water conservation and sustainability are geopolitical issues. While water itself may not be expensive, Bohlen warns that waste water can become expensive to discharge, if allowed at all. Electrical power costs vary worldwide, and gas costs differ if delivered in liquified form rather than piped in as natural gas.
When considering areas where cost savings can be made, Bohlen says premium high-efficiency electric motors, direct drive fans and variable frequency drives help to reduce power consumption when full output of the pumps or blowers are not required. While oil coalescers, belt suction devices, split rinses and drag outs with multiple small pumps may require more power, they normally pay back with chemical savings and water reduction goals.
Reducing water consumption is best achieved with pre-treatment, says Bohlen, who suggests that the optimum water back-flow system is where flow is controlled in response to can throughput. This function matches water consumption to the metal surface being processed and in modern can washers, gravity back flow further reduces electrical usage.
Bohlen also suggests a change to reverse-osmosis (RO) water rather than de-ionised (DI) water since, although there is an electrical power cost to RO, the reduction of effluent from resin column regeneration could help with overall water reduction.
Washers are generally hot water or steam heated, and utility consumption is largely driven by tank operating temperatures, says Bohlen. When the chemical system is set up properly, the temperature can be set at the chemical supplier’s minimum recommended level. When problems arise, he suggests checking the chemical set-up, spray pressures, spray pattern and looking for clogged nozzles rather than raising the tank temperature.
Chemical costs are influenced by factors such as water hardness, use of treatment chemicals, surface condition of the wash stage, cleaning problems with the bodymaker coolant and the possibility of switching away from common fluorides. A reduction in chemical consumption will also provide reductions in water and waste water treatment costs, says Bohlen.
Dryer fuel consumption is mostly a function of operating temperature, the volume of water being evaporated and the exhaust rate – all three factors accounting for around 70 percent of the heat load. Bohlen dismisses suggestions that making savings in heat losses through the insulated walls of the dryer is worthwhile when just five percent escapes.
Cutting energy consumption in the dryer is achieved by reducing the water, exhaust rate and operating temperature. The dryer’s heat load can be reduced with the use of a synthetic Kevlar conveyor belt, which doesn’t absorb heat or releases it in a similar manner to metal belts.
Bohlen reckons that, based on this approach, washer/dryers should be able to process 2,400 cans per minute at a cost of 75 US cents per 1,000.
More information from Cincinnati Industrial Machinery, 4600 N Mason-Montgomery Road, Mason, Ohio 45040, USA. Tel: 1 513 923 5601.