This document summarizes a presentation on conveyor safety given at a mechanical engineering seminar. The presentation discussed advances in conveyor design that have increased complexity, challenging safety. It emphasized that simplicity yields reliability and safety. The presentation also described control system challenges on conveyors presented in three case studies, highlighting the need for rigorous risk assessment and closer collaboration between mechanical and electrical disciplines to develop safe isolation procedures for conveyors.

1. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
Safety and Isolation for
Conveyors into the Future
Edmond O’Donovan
25th September 2018

2. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
Outline of the Presentation
• No Risk No Control
• Advances in Conveyor Design
• Safety Implications of these Advances

3. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
No Risk - No Control
• If it’s not there, it’s not a risk
• If it’s not there it also can’t Fail
• It also does not need to be maintained

4. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
Simplicity in Design
Yields Reliability & Safety
• Drive Down the Component Count
• Simplify the Controls
• Thoroughly Document What is Built

5. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
More of This

6. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
Less of This

7. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
Advances in Conveyor Systems
Typical Conveyor 25 Years Ago
• 1,000m Long
• Uniformly Uphill/Flat
• 2,000tph
• Dual 250kW
• Delay Fill Fluid Coupling Drives

8. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
Typical Conveyor Today
• 5,000m Long
• Complex Geometry
• 5,000tph
• Multiple 750kW Drives

9. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Length (m)
-80
-60
-40
-20
0
20
40
60
80
100
120
Lift(m)
Panel 1
2 x 630kW
2 x 630kW
2 x 630kW
2 x 630kW
1 x 50kN.m
1 x 40kN.m

10. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Length (m)
-80
-60
-40
-20
0
20
40
60
80
100
120
Lift(m)
Panel 1
MG S7

11. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
Isolation Challenges
• The potential to store energy between Drives/Holdbacks and Brakes is
Significant
• Releasing a Brake (or the Winch) can result in Multiple, Significant,
Uncontrolled Movements around the Conveyor
• Standard Isolation by Locking Out the Electrical System Provides NO
Protection
• Procedures to De-Energise the System Need to be Developed by Rigorous
Risk Assessment

12. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
-10
0
10
20
30
40
50
60
70
80
0 2500 5000 7500 10000 12500 15000 17500 20000 22500
Lift(m)
Length (m)
2 x 1000kW
1 x 40kN.m
2 x 1000kW
1 x 250kW
1 x 40kN.m1 x 40kN.m

13. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
Long Conveyor Isolation Challenges
• All the Challenges of Short/Underground Conveyors
• Additional Challenge of Locked in Thermal Stresses
• Even if Relieved, These can Re-Develop as the Temperature Changes
• Procedures to De-Energise the System, and Keep it De-Energised,
Need to be Developed by Rigorous Risk Assessment

14. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
Control System Challenges
Case Study No 1
• Slightly Downhill Maingate System.
2,000m Long, 4,000tph
Brakes After the Take-Up and on an Intermediate Braking Tripper
-20
-15
-10
-5
0
5
0 250 500 750 1000 1250 1500 1750 2000
Lift(m)
Length (m)
Braking Tripper

15. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
Control System Challenges
Case Study No 1 (cont.)
• Tripper could not be de-selected if it was physically
connected
• Despite the best efforts of the controls people, a genius
figured out a way to do this.

16. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
Control System Challenges
Case Study No 2
• Slightly Downhill Maingate System.
2,500m Long, 4,500tph
Brakes Located on the Tail/Boot End Pulley
• To Enable the Brakes to be Lifted when the LW Substation is
off, the brake hydraulic system was powered from a
compressed air turbine. And lifted through the signal line
• Multiple control system defeats resulted in a near tragedy

17. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
Control System Challenges
Case Study No 3
• Standard Setup.
4 x 320kW.

18. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
Control System Challenges
Case Study No 3 (cont.)
• Both Drives Started to Slip
• Slip Detection Worked Perfectly
• Old Regulations Allowed Drives to Slip for up to 20s
• Conveyor Slowed to around 70% Speed
• Drive Pulleys Grabbed

19. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
Control System Challenges
Case Study No 3 (cont.)
0
50
100
150
200
250
300
0 250 500 750 1000 1250 1500
%RatedTorque
RPM
Torque When Drives Grip
Torque When Drives Slip

20. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
Case Study No 3 (cont.)

21. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
Case Study No 3 (cont.)

22. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
Case Study No 3 (cont.)

23. 28th Mechanical Engineering Safety Seminar – No Risk No Control – 25th September 2018
Conclusions
• Both the Mechanical and Electrical Complexity of
Conveyors is only going to increase
• Simplicity is a key to safety, as well as reliability
• Mechanical Isolation/De-Energising needs to be
considered far more seriously
• Closer interaction between Mechanical & Electrical
disciplines will be required to achieve acceptable
safety outcomes
• Historical Requirements need to be Rigorously tested
to ensure they are still appropriate