“It is no use running the process at excessive pressure just in case.”
“Compressed air falls into the same category as electricity: it is required to keep our process going; but compressing air is not our core skill,” says the Maintenance Manager of the Karhula Foundry of Sulzer Pumps Finland Oy.
Sulzer Pumps is a world-leading pump designer and manufacturer, established in 1834. Its foundry, pump factory, service centre and research laboratory in the Karhula industrial park meet industrial pump and mixer needs all over the world. The Karhula foundry casts acid-proof and high-alloy special steel at a rate of about 50,000 castings annually.
The foundry uses compressed air in grinders, hand tools, pneumatic transmitters, filter cleaning, and occasionally also in large amounts in AOD converter cooling. Melting takes place a couple of times per work shift i.e. four times a day, so consumption fluctuates greatly.
“We now compress air with three screw compressors, two of which provide the basic load, and the third one, a speed-regulated compressor, evens out the load fluctuations. The total compressor capacity is 109 m³/min, and the compressed air is treated by four adsorption dryers and filters.”
A significant component in the present compressed-air system is the control and monitoring system, Sarlin Balance, which keeps the pressure steady.
“It is no use running the process at excessive pressure ‘just in case’,” the Maintenance Manager reminds.
“We agreed last winter that the pressure level would be lower than 6.5 bar by autumn. We started in January in increments of 0.1 bar, and the level is 6 bar now, which already yields significant energy savings. It can certainly be lower still.”
“But if my phone starts ringing,” says the Maintenance Manager, “that will be the end of dropping the pressure further. Reliability is absolutely vital in all our processes. We also provide compressed air to other companies in the Karhula industrial park, and the supply must be unbroken and reliable.”
When air demand rises, Sarlin Balance engages the stand-by capacity and then disconnects it as soon as the situation is normal again. Sarlin Balance provides comprehensive data about the system status, and can be programmed to raise alarms via SMS to mobile phones.
When the new system was launched, the entire network was searched for leaks, and dozens of leak points were discovered. The cost of repairing leaks is often marginal compared to the expense they cause. When leaks are eliminated, a lower pressure level can be maintained, which, of course, saves energy.
“We are still looking for added savings by optimising the pressure level and by introducing a dual pressure system: the air demand is low at night, and we could drop the pressure level then. On the whole, we are very happy with the solution. We save energy and other costs, and our operational reliability has improved.”