Great benefits when planning maintenance
The processes in the Rautaruukki Raahe production plant continue day and night. The furnaces, smeltery and rolling mill produce steel, and the power plant provides energy for them. An unseen production factor is compressed air; it is constantly required even during a shutdown.
“Loss of compressed air would be a catastrophe for us,” says Ruukki’s Work Planner.
“We have about 50 compressors, 19 of which are in the common system that serves the main processes in the plant.”
Ruukki uses compressed air in many and various tasks ranging from on the steel lines down to cleaning the lens of the camera that monitors temperatures. The air demand never ends, not even when the production processes stop.
“Our compressors used to increase network pressure whenever the air demand decreased.”
Ruukki started to survey its system and plan its control already in the 1990s. Sarlin was able to offer extensive proficiency in compressed air and experience in the use of the Sarlin Balance control system. The target when purchasing the system was to save 10% of energy costs, resulting in over 150,000 euros annually. Sarlin Balance has been working more than a year now, and the reports show that the savings target has been reached.
The pressure level was already fairly low to begin with, but could be dropped further with Sarlin Balance; the present level is 5.65 bar, except for the rolling mill which requires 6 bar.
“We experienced some initial surprises.” the Ruukki staff remember. “The power plant men would phone us asking what had happened to the compressor; its noise changed. The compressor had started to unload, and the men had never experienced that. This showed that unnecessary loading could be eliminated by Sarlin Balance.”
There were initial problems with compressor starts, as the units were not accustomed to stopping; they had always been running continuously. But soon the running sequences were organised, and Sarlin Balance yielded further benefits beside energy savings. The Work Planner finds centralised information a great benefit:
“You can check the overall status on the control room monitor the first thing in the morning. If there is a problem, you can rectify it before the operating staff are there to give the alarm. Earlier, the service men had to go around the compressor stations to know whether all compressors were running and whether there was enough compressed air to keep production running.”
“When you go and look at a unit on the spot, you only see how it is running at that moment. Sarlin Balance saves all the trend data from dew point fluctuations, compressed-air output temperatures etc. This is a great benefit when planning maintenance. We are able to intervene before problems arise in the production departments.”
“Balance also gives us graphical information about the resources and unused capacity of the compressed-air system in terms of extending it. The rolling mill has two new compressors which will also be connected with Sarlin Balance. The power plant, too, added two further compressors, as the air demand in the furnaces has increased.”