Providing SIL3 protection for mine hoist systems

30 December 2020

A safety programmable logic controller (PLC) has enabled a series of mine hoist systems to attain the highest SIL3 functional safety certification.

The three functional safety systems cover speed and position monitoring, additional protections using emergency stop functionality that incorporates mine shaft safety devices and a SIL 3-certified mine hoist brake system.

The new SIL 3 Hoist Monitor (SHM) is said to provide accurate safely limited speed, position control, acceleration and deceleration for a mine hoist, replacing a traditional system. It uses PROFINET/PROFIsafe safety encoders connected to the AC500-S safety PLC. 

SHM is implemented using safe function block diagrams and structured text programming languages which can help reduce development times, offering greater flexible when creating complex safety logic.

In addition, fast safe floating-point calculations and trigonometric functions enables the mine hoist to run quickly – up to 20m/sec. 

The AC500-S is also able to protect against overspeed and over- or under-winding by running within safe limits set by the control system. Should the control system fail to stay within the pre-defined safe speed, position, acceleration or deceleration range, the safe hoist monitor triggers the safe machine stop and applies the mine hoist brakes to bring the hoist to a safe stop. For drum hoists, additional safety protection is provided for functions such as correct coiling supervision and clutch monitoring.

An advanced version of SHM, called the SIL 3 Hoist Protector (SHP), is available which uses emergency stop functionality, specifically tailored for the given mine hoist installation and customer functional safety requirements. The AC500-S safety PLC provides a safe, flexible configuration, with pre-certified functional safety protections. 

The SIL 3 certified Safety Brake System (SBS) features up to four independent and redundant mechanical and hydraulic systems. Each system (channel) is controlled by a separate safety controller, making up a complete SIL 3 brake system. To synchronise multiple safety controllers, safe communication with more than one master system is required. To address this ABB provides safety CPU modules that function as both a safety controller and a safety device using PROFINET/PROFIsafe shared device functionality.

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