Interface network survives tough environments

Edited by the Engineeringtalk editorial team Jun 8, 2006

Control Lubrication uses AS-Interface to network proximity switches, zone valves, pressure switches, flow monitors and mobile plug-in reset pushbuttons in some of the toughest environments possible.

Control Lubrication, a Yorkshire-based system integrator specialising in lubrication systems for machinery in heavy duty industries, is using AS-Interface (Actuator Sensor Interface) to network proximity switches, zone valves, pressure switches, flow monitors and mobile plug-in reset pushbuttons in some of the toughest environments you could imagine.

One example is at Cleveland Potash - based at Boulby Mine, Saltburn, UK - where the company wanted to ensure all the hanger bearings that support the Archimedes screw conveyor shaft received the correct amount of grease every 60 minutes.

The product being conveyed can find its way into the bearing through the seals, so the bearing must be surrounded by a grease labyrinth to keep out any debris.

The replenishment of grease is essential, because if a single bearing should go down it would cost hours of production down time due to the difficulty in changing them.

To do this effectively by manual means was impossible due to the high levels of salt in the atmosphere and the working environment of up to 40C.

Instead, a centralised dual line lubrication (DLL) system was used.

The DLL system uses two grease lines to operate the grease injectors.

Using a diverter valve, the pump pressurises one line forcing grease into one side of the injector, this causes a piston inside the injector to move and dispense a measured amount of grease from the other side of the piston.

The movement of this piston actuates a switch confirming its operation.

When all the injectors on the system have been actuated, the line pressure rises to a switching point and stops the pump.

After a set period of time the pump is started again, the diverter valve switches to line two and the pressure in the line forces all the pistons back, dispensing grease from the other side of the piston and so on.

If any one of the switches is not activated an alarm is set to alert maintenance personnel.

If for any reason a bearing didn't receive the required grease, the control system gives out an alarm message stating which lubrication device was at fault.

An AS-Interface network designed and installed by Controlled Lubrication consisting of a range of pneumatic modules, a PLC and HMI supplied by LC Automation was installed to provide the feedback from each lubrication device.

AS-Interface is a highly efficient single cable networking alternative to the hard wiring of field devices.

It is extremely simple to install and produces savings in wiring installation time and costs.

Despite the extreme corrosive conditions the AS-Interface equipment, which meets IP67 rating, has worked without any problems.

The system had been running successfully for three years.

"The dual line lubrication (DLL) system from Controlled Lubrication has been extremely reliable despite the continuous harsh working conditions".

"This is essential to us as downtime can be extremely costly".

"The AS-Interface networking equipment has been unaffected by the environment as well", said Graham Beadle, Mechanical Maintenance Engineer, Cleveland Potash.

In 2005 the lubrication system was extended to feed the vibromotors on the hoppers, which required grease every four hours.

An AS-Interface air module was used to control a pneumatic zone valve to not only control the supply of grease, but also to receive an input from the grease confirmation switch.

The system is now at AS-Interface's 100m network limit.

At present the system doesn't cover all the critical bearings, however Control Lubrication is confident that if these needed to be connected they could be without the need for repeaters or line extenders.

"AS-Interface is a mechanically oriented system that is extremely easy to install and offers more than enough power for the lubrication applications".

"The equipment is being successfully installed in the harshest of conditions that can cause serious problems for traditional hard wiring", said Andrew Hoyle, Managing Director, Controlled Lubrication.