Cost-effective risk reduction with trapped key interlocks

Can you make safety modifications on machinery that might be ageing, without a massive overhaul? Well, in some cases, it is possible to make practical, budget-conscious improvements - especially when working with legacy machines - while still achieving a high level of protection for personnel and meet machinery safety standards and regulatory requirements.

Fortress Safety helped a company with upgrading a 50-year-old concrete mixer. A facility needed to install a second set of blades to make cleaning easier. However, after a risk assessment it became clear that there was a high potential for severe injury. These new blades would be within easy reach, potentially exposing personnel to a hazard if the machine were to run while the guards were open.

The replacement of the control system to automate and monitor guard safety would cost in the excess of $300,000 - an unrealistic option for such an old machine. Fortunately, there are cases where risk reduction can be accomplished without changing the machine control system.

A mechanical trapped key system offered a simple, low-cost solution. This type of risk reduction measure is particularly effective for older machines where upgrading the control system is impractical.

Trapped key interlocking is a tried and tested method of mechanically safeguarding machines and processes. Mechanical keys eliminate most of the electrical wiring associated with other types of interlocks making them cost effective to install.

The Fortress Safety mGard trapped key system is a flexible solution that can be adapted to enforce specific key sequences depending on the unique requirements of different applications. This means that the system can be configured to require the predetermined sequence of operations. This ensures accurate compliance with security procedures. Different configurations can be designed to provide solutions for specific needs. Key benefits of mechanical trapped key interlocks include:

- Physically preventing the machine from operating until all safety conditions are met

- Ensuring access doors can only be opened once power to the system is turned off

- Enforcing a key sequence to manage access to areas with hazards

- Preventing accidental re-energising of the machine while the guards are open

Not only did this solution reduced the risk of unexpected start-up of the mixer and eliminate the need for a full control system overhaul, but it also provided considerable monetary savings. The final cost for the entire upgrade, including the new blades and interlocks, was under $1,000, which is a fraction of the cost of a full retrofit. And it brought the equipment into compliance while significantly enhancing worker safety.

As the concrete mixer example shows, mechanical solutions, thoughtful planning and proper use of safety standards can deliver major safety gains, even on old machines. Fortress Safety brings extensive expertise in designing and supplying trapped key interlock systems that can meet each application's requirements.

The mGard range of mechanical trapped key interlocks, made from durable metal alloy (with stainless steel options available), is built to perform even in the most demanding environments. mGard interlocks can be seamlessly integrated into both new installations and legacy equipment, providing a robust, cost-effective safety solution, suitable for use up to SIL3 (IEC 62061) and Category 4 PLe (ISO 13849-1).