Keeping safe and productive

19 October, 2022

I spend my time looking at technologies and applications to ensure manufacturing plants are efficient and the people who work in them are kept safe. It is encouraging to see that both these things are improving; workplaces are becoming safer and more productive.

We have been able to automate tasks and enbed control of the process and safety together in the control system. Operators are no longer required to disconnect the isolator to a manufacturing line before carrying out a task. Instead, the control system brings the line to an appropriate point and specially designed parts of the control system ensure hazards are not present while the operator is allowed access.

This concept of functional safety is not new. The type A standard that gives guidance on this approach was first published in 1998. Moreover, thanks to effective education by leading manufacturers of safety relays and safety PLCs these devices are now ubiquitous in control panels.

Three stages

Functional safety systems are based on three stages: inputs, logic and outputs. A typical system comprises an interlock or light curtain monitored by a safety relay or safety controller opening a contactor or holding a motor drive in a safe state.

The electrical engineer for the project will design relevant components into the control panel and carry out calculations to ensure the reliability of the system and validate its operation, proving that faults in the system are identified and there is redundancy in place to keep everyone safe under fault conditions.

The fluid power connection

So far, this article looks a little out of place in a periodical for the hydraulics and pneumatics industry. There have been references to PLCs, light curtains and control panels, all of which are electrical, and it is this that concerns me. Fluid power presents hazards the same as electrical energy does. Injuries caused by crushing or fluid injection can be devastating.

However, my experience from visiting sites is that these risks are not dealt with equally. I regularly see dual-channel interlocks and light curtains on the guarding, the panel contains the yellow or red flashes on the controller indicating safety devices and the contactors have redundancy all correctly monitored. However, the output from this safety system goes to standard valves, with no monitoring.

It only takes a single fault, a small piece of debris in the media stopping a spool from shuttling for example and whole safety system is defeated, exposing users to hazards. Although this paints a gloomy picture of fluid power being left behind by its electrical counterparts, there are major strides being made to correct this.

British Standards are considering a new document, giving more guidance than is currently available in ISO4413 and 4414. I have been working with the British Fluid Power Association (BFPA) to raise awareness in the industry, and with the National Fluid Power Centre to give the best training we can to the hundreds of engineers and apprentices that undertake its courses.

Training

Fortress Safety is also running fluid power safety courses alongside its existing portfolio of practical, application-based machinery safety training. In my experience of working with engineers, once they are aware of the potential issues, implementing appropriate systems is straightforward.

The risk assessment is reviewed to ensure that it includes the relevant entries and, in most applications a, block and bleed or safe exhaust safety valve can be installed in the system.

The input and logic parts of the safety system are usually in place and the valve is operated safely and the monitoring of its state is carried out just as it would be on a safety contactor. By purchasing a safety valve from a reputable manufacturer, all the necessary component testing has been undertaken and the safety data is ready to be included in the calculations to ensure the Performance Level or Safety Integrity Level meets the requirement of the system.

Testing of the fluid power parts is then carried out with the rest of the safety validation. We are now working with many customers where this approach is being used on all new projects and just as easily applied retrospectively, installing the valve before an existing valve stacks.

There are of course many different applications, but Fortress Safety has a team of product and machinery safety experts on hand to support you with these. Everyone has a duty to keep their colleagues safe and I am proud of the work we do at Fortress to provide the best safety solutions to allow everyone to achieve this.

Safety and productivity have come a long way, and with a little more awareness and some small changes we can continue to take big steps in the right direction.

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