How to cope with frequent safety standard changes

To help companies meet changing safety standards and specifications a turnkey management approach has established for the design, installation and commissioning of safety systems.

Integrated Safety Solutions (ISS) is an independent company that specialise in the complete management of safety projects relating to processing plant and machinery safety.

Frequent changes and additions to Safety Regulations and Standards, coupled with the introduction of new safety technology, make it difficult for companies looking to introduce new or up-grade existing processing plant and machinery to choose the most cost effective safety control systems.

Of primary consideration will always be the need to ensure the design and use of plant and machinery is inherently safe, that it meets the organisations production requirements and that it is compliant with the relevant Health and Safety Regulations and Standards.

To help companies achieve this objective ISS provide a turnkey management approach to the specification, design, installation and commissioning of safety systems for processing plant and machinery.

A recent project undertaken by ISS to design and install the safety control system for a robot materials handling station provides a good illustration of the scope of a typical safety related turnkey project Game Engineering, a materials' processing and handling engineering company based in Lincolnshire, had been contracted to design and build an automatic robot station.

The function of the robot was to off-load large sacks of bird seed from a conveyor and to stack them on pallets located either side of the robot.

Full pallets were then removed from the robot cell by forklift truck (FLT).

The first stage of the project was to draw up a comprehensive safety specification and to agree the operational requirements of the machine with Game Engineering.

This included, the full range of its foreseeable use, potential misuse and possible malfunction of the machine.

The next stage was to identify all the hazards associated with the operation of the robot cell, identify the relevant "Essential Health and Safety Requirements" as required by the Supply of Machinery (Safety) Regulations 1994 and undertake a risk assessment to quantify the risks.

Having identified and estimated the main areas of risk, a combination of different protective measures were evaluated to determine if the required level of risk reduction would be achieved - taking into account: * the probability and severity of injury arising from a failure of a safety function.

* the ability of the machine to perform its intended function with the control measures in place.

* the control technology used in the operation of the machine.

* the usability of the machine from the operators perspective.

* the overall cost, effectiveness and reliability of the safety related control measures.

An important factor when considering the reliability or performance level of the safety system was the need for frequent human interaction because of the use of an FLT to remove the stacked pallets whilst the robot remained active in an adjacent cell.

The final specification for the safety control system, agreed with Game Engineering, was to create three monitored zones within the operating field of the robot using a combination of fixed perimeter guarding, type 4 light curtains, electrical interlocks and emergency stop switches.

At the heart of the safety system was a programmable safety PLC used to monitor the position of the robot arm and the condition of the other safety components.

It also activates the relevant light guards to ensure the robot could not operate in a zone when an FLT was present and powers down the robot in the event of a hazardous condition.

A safety PLC, which is regarded as a high complex system, was chosen to monitor and control the safety functions because it conformed to a Safety Integrity level 3 as defined by the standard IEC 615081.

The operating characteristics of the safety PLC also combined with the other safety components to provide a category "d" performance level for the overall system as defined by ISO 13849-12.

Which, in turn, provided the required level of risk reduction as calculated using BSEN 10503 and defined by BSEN 121004 Another benefit of using a safety PLC, over the more traditional individually wired safety relays, was the considerable savings in component and installation costs.

In summary, knowledge and understanding of current safety Standards and Regulations coupled with the application of new safety technology enabled Game Engineering, with the help of ISS, to incorporate a reliable and cost effective safety control system into their robot materials handling station.

1 - Functional safety of Electrical/electronic/programmable electronic safety-related systems.

2 - Safety of machinery - Safety related parts of control systems.

3 - Safety of machinery - Principles of risk assessment.

4 - Safety of machinery - Basic concepts general principles of design parts 1 and 2.

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