FEATURE u Machine Building
Complete skip drive solution offers superior control
Increasing the safety and reliability of quarrying operations
M
otion control is paramount in hazardous industries like quarrying. If a skip laden with a ton and a half
of product were to go hurtling off its rails at 80mph, the consequences could be devastating. Here’s how motor and drive manufacturer WEG and the company’s premier partner Technidrive, developed a new skip drive with a brake control solution to upgrade TH Moore (Contracts) Ltd’s quarry equipment to improve reliability and safety on site. TH Moore is a supplier of quarry materials, high grade aggregates and CE marked bituminous products. Before the project, the quarry in question used an outdated skip drive system on a set of rails powered by a motor to move product on site. The system saw a skip drive up the rails to sit below a mixer or above three different bin positions — one used for loading straight into a lorry and two for storage bins. The system’s usage was dependent on
the product, operational intermittently with no set running hours. Plagued with a wide range of electrical problems, and equipment breakdowns leading to multiple safety concerns, these faults were made harder to identify and rectify as the system was only operational for two to three months each year. An entire system upgrade was necessary. Technidrive was brought on board to design and commission a new skip drive solution and control system with a programmable
22 September 2022 Irish Manufacturing
logic controller (PLC) and full touch screen integration. The company turned to its long- term partner WEG to supply a motor and a variable speed drive (VSD) for the skip upgrade project.
One of the main problems associated with the old system was the excessive brake wear on the skip motor, as it wasn’t used with a VSD. If an operator selected bin one and pressed start, the skip would firstly drive down to the mixer. As soon as it would hit the limit switch it would slam the brake on and disengage the motor, resulting in a harsh stopping time. Once the system had sent the message that the deposit was complete, it would then engage the motor and run harsh acceleration to drive up to bin one’s position. For the upgrade, Technidrive turned to WEG
who provided a 22kW 4 pole B5 cast iron brake motor with an integrated 1024 pulse encoder. With superior efficiency levels, this motor was selected as it offers excellent cost effectiveness, greater productivity and the durability required for quarrying applications. For the skip drive, WEG recommended the CFW700 VSD with integrated high torque brake control. This integrated brake control, along with some intelligent programming of the on board soft PLC, means that Technidrive have been able to virtually eliminate brake wear and significantly reduce motor maintenance. The new skip system features an auto slow down function, which allows the motor to stop
on the VSD before the brake is applied. Now the brake is only used as a holding mechanism and the system is no longer driving against an engaged brake. Furthermore, virtual positions programmed for each location, allow for a slow ramp up using the VSD. Before the skip arrives into its final position, the new system leaves space for slow down. This allows the skip to stop from a slower speed in the same position every time. This has further reduced wear and tear on the mechanical system.
REPLACING AN OBSOLETE SYSTEM Another glaring issue with the old system was that it used an outdated, unreliable and obsolete PLC system. This meant that if there was a digital input or card that went faulty, replacements were not readily available. The original PLC system worked off a series of limit switches used as part of the control system as a safety interlock. Technidrive designed a new PLC system that was able to read the encoder. The new system features a 10-inch Hitachi human machine interface (HMI) instead of a series of push buttons and controls on a busy panel.
Due to the encoder feedback and the live skip position function, the operator knows exactly where the skip is at any point. This results in easier and safer control between the four positions, visible on the touch screen display.
WEG
www.weg.net
www.irish-manufacturing.com
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
