Feature Drives & Controls


Keeping environCom hammering I


environCom, operator of the UK’s largest e-waste recycling plant, called on the services of Ralspeed following the failure of a 335kW AC variable speed drive on its hammer mill


nconveniently for environCom, the failure of the drive in question occurred over the Christmas break. However, once Ralspeed were called in, the company’s experienced engineers quickly located the source of the problem and supplied a replace- ment control panel, complete with a new drive, which was installed and commissioned less than three weeks after the original problem occurred. The hammer mill at environCom’s plant in Grantham is a key element of its operations at the site, which has the capacity for reprocessing up to 100,000 tonnes of waste electrical and electronic equipment (WEEE) per year. The mill is used to break down almost all of the waste handled on the site, which ranges from washing machines and electric toasters to televisions and computers, and when the mill is out of service, this causes serious disruption to the company’s operations. The failure of the mill’s AC variable speed drive in late December was therefore a major issue, and environCom contacted several poten- tial suppliers in an effort to find one that could help with remedying the problem quickly and cost effectively. On inspecting the failed drive system, Ralspeed’s engineers discov- ered that the principal reason for fail- ure was that all of the ventilation channels in the drive power sections had become blocked by the dust pro- duced during the operation of the hammer mill. This had led to the over- heating and failure of two converter modules, putting the existing drive beyond economic repair.


Ralspeed adopted the approach of arranging for the panel to be vented to clean outside air via ducting. In spite of the proximity of the holiday season, Ralspeed was able to source the new drive rapidly from Vacon UK, and then worked flat-out to complete and test the new panel, which was delivered to the environCom site early in January. “Throughout this whole project, we had outstanding support from Ralspeed,” said David Baldwin, head of engineering at environCom, “and we were very impressed by the com- pany’s ability to react quickly at what is, for any business, one of the most difficult times of the year. In fact, I think it would have been very diffi-


Automation JUNE 2013


cult, if not impossible, to find any other company with the capability and expertise needed to get our plant back up and running in just three weeks - let alone do it at such a com- petitive price.”


Taking control


In another major project for Ralspeed, the company has also developed and supplied a custom control system for use on the UK’s largest slurry tank. The tank, which was designed, manu- factured and installed by slurry han- dling specialist, Storth, is 40m in diameter, almost six metres high, and is capable of holding over seven mil- lion litres of slurry.


Slurry - which is essentially farm animal excrement mixed with water - is stored in the tank at certain times of year as an environmental protection measure, and then used on farmland at other times of year, where it acts as a valuable natural fertiliser that is rich in nitrates. Pumps are used to control the flow of slurry into and out of the tank, which is also equipped with motorised agitators to stir the slurry periodically during storage. To provide the control system for the pump and agitator motors, Storth approached Ralspeed, which had sup- plied control systems for a number of earlier Storth projects.


For the new slurry tank, the design of the control system had to take into account the limited capacity of the mains supply at the tank installation site. This meant arrangements had to be made to limit the inrush current when starting the pumps and agitators, and also to ensure that no more than


Above: the hammer mill at


environCom’s


Grantham plant is a key element of its operations at the site, which has capacity for


reprocessing up to 100,000 tonnes of waste electrical and electronic equipment (WEEE) per year


Below: the tank, which was designed,


manufactured and installed by slurry handling specialist, Storth, is 40m in diameter, almost six metres high, and is capable of holding over seven million litres of slurry


two agitators could run at the same time, and that the agitators could not run when the pumps are running. Storth also wanted to be sure that the agitators had approximately equal usage, in order to equalise wear and tear, thereby maximising their operating lives. Further requirements were that the control system should be as simple as possible to facilitate maintenance, and that the user controls should be straightforward and intuitive. To meet these special requirements, Ralspeed designed and built a fully customised control panel. The com- pany used 18.5kW Torq-master soft starters from its own range to control the motors. These units provide con- trol over the motor starting current, ensuring that the capacity of the supply is never exceeded, and also ensuring that the agitators and pumps start and stop smoothly.


Because no more than two of the motors on the tank could ever be run- ning simultaneously, the Ralspeed engineers realised that substantial cost savings could be achieved by using only two soft starters, and connecting them, via main contactors, to the appropriate motors as needed to meet operational requirements.


Ralspeed was able to provide a single selector switch to configure the operation of the system. This switch allows the user to rotate the duty of the agitators, and also to select operation of the pumps instead of the agitators when necessary. With careful design, it proved possible to implement this straightforward and effective form of control without needing to use a PLC or smart relay, thereby satisfying the end user’s request for simplicity.


Ralspeed www.ralspeed.co.uk T: 01254 582 345


Enter 208 19


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56