Adopt Machine Safety standards now, says Pilz

As the Machinery Directive EN 13949-1 standards better reflect state of the art in Machine Safety System design, machine builders should adopt these standards sooner rather than later, says Kevin Ives, Machinery Safety Consultant at Pilz Automation Technology.
 
The latest version of the Machinery Directive has now been with us for some time. 2006/42/EC was introduced in 2006 and published in the "Official Journal" (OJ) in September 2009. The publishing of any article, directive or notification of a standard in the OJ is the point at which the use of the document becomes mandatory.

Adopt Machine Safety standards now, says Pilz.

Ever since the first Machinery Directive, the recommended method of meeting all of the Essential Health and Safety Requirements (EHSR's) was to follow the advice in the "Harmonised Standards". These are standards that have been written in support of the directive. A list of the standards applicable for use against the directive is printed in the OJ following the ratification of the directive.
 
As with the directives, the standards are being improved/upgraded with new versions being announced in the OJ as being harmonised against the relevant directive. In 2007, the long awaited replacement for Safety of Machinery - Design of safety related control systems EN 954-1 was printed. This standard, EN 13949-1, has the same title and seeks to achieve the same ends but uses a risk-based approach. The standard introduces new criteria such as Diagnostic Coverage (DC) and Mean Time To Dangerous Failure (MTTFd), which need to be taken into consideration when designing the system.

The normal situation, when a standard is rewritten, is to allow a two-year "change over" period. This is provided to enable manufacturers to modify their design and documentation to align with the new requirements. Using this rule, EN 954-1 should have been revoked and replaced by EN 13849-1 in late 2009. The inclusion of EN 13849-1 as a harmonised standard against 2006/42/EC was announced in the OJ in September 2009.
 
At this point, the problems started to emerge. There were a few complaints made to the commission claiming that two years did not allow sufficient time for some manufacturers of components to provide the information and data needed to calculate failure rates, as required by the latest standard. The commission agreed and therefore delayed revoking EN954-1 until the end of 2011. The latest list of harmonised standards that can be used to demonstrate compliance with the directive, does not list EN 954-1. This list was printed in the OJ dated 20^th October, 2010. This clouds the issue further. In theory, manufacturers cannot use standards that are not harmonised to claim compliance with the directive, but EN954-1 will not be revoked until the end of 2011.

All of the machine-specific standards (C standards) that were written before the introduction of EN 13849-1 list EN 954-1 as an appropriate standard to use for the design of the safety-related controls. This raises even more confusion.
 
As the newer standards better reflect state of the art in Machine Safety System design, Pilz therefore recommends that machine builders adopt these standards sooner rather than wait until the end of the transition period. Why? Because we believe the future of automation and machinery lies in flexible, modular architectures, which will provide users with the high level of availability and adaptability required for agile, lean manufacturing plants. Modern plant and machinery will therefore require intelligent safety systems.
 
The new standard reflects this increased tendency to use electronic and programmable systems for safety rather than traditional electromechanical devices that were used when EN 954 was published. EN 13849-1 provides requirements for the design and integration of safety-related parts of control systems, including software. It has wide applicability as it applies to all technologies, including electrical, hydraulic, pneumatic and mechanical.
 
While acknowledging the decision of the EU, we believe that the probabilistic approach of the new standards provides machinery designers and users with many advantages when assessing the reliability of safety systems. While there is an increased complexity in requirements to make design calculations, tools such as Pilz's PAScal Safety Calculator are available to calculate the required Performance Level (PL) and Safety Integrity Level (SIL). This software also evaluates a safety system designs and then generates the necessary documents to be included in the machine's technical file. Training courses are also available on the new Machinery Directive 2006/42/EC, including one, two and four-day City & Guilds Machinery Safety Courses, Safety Design and CE Marking.
 
Furthermore, those companies designing and manufacturing new machinery who apply one of the new standards now, will not incur additional costs of design, validation, and documentation when the transition period ends in December 2011.

For further information, e-mail: v.smith@pilz.co.uk or view website: www.pilz.co.uk  Refer to page 178

Ensuring a much safer working environment
for operators of a hand-fed platen (die cutting) press

With the Health & Safety Executive about to commence on-site inspections of hand-fed platen presses, users of this high-risk machinery need to ensure that their presses meet the required safety standards. By working closely together, two companies have developed a novel, high integrity safety solution for a hand-fed platen press, which uses an array of light beam sensors and a modular safety control and monitoring system.

A collaborative development project between two UK-based companies has resulted in a much safer working environment for operators of a hand-fed platen (die cutting) press.

Refer to the two pictures: High integrity safety solution for hand-fed platen press, based on Pilz's PNOZmulti modular safety system.

In November 2009, machinery safety specialist Pilz Automation Technology and SCA Display UK, a manufacturer of Point-of-Display (POD) products for retail customers, began working together to improve the safety of a hand-fed platen press at SCA Display's production plant in Shenstone.

Part of SCA, SCA Display UK's Shenstone plant employs around 80 staff and manufactures a wide variety of point-of-sale and POD products, mostly custom designed products made from cardboard. The factory uses a wide range of machinery, including digital and silkscreen printers, die cutters, folding & gluing machines and platen presses. Most of the die cutting uses semi-automatic presses, but one of the presses is hand-fed, which is used for short runs and one-off customer specials.

Ian Clews, Facilities Manager at Shenstone, has been working with platen presses for more than 30 years and SCA are members of the Confederation of Paper Industries, where machinery safety is high on the agenda. "Quite frankly, the use of these machines has been a concern for many years, particularly in the dwell mode. With two fatalities in the UK in recent years, users of these machines need to review their safety systems."

"A typical hand fed platen press closes with a tremendous force, often with the operator's body in close proximity. This means that operator safety is extremely critical. At Shenstone we have a continual improvement policy which instigated further upgrades to our platen press to ensure that additional operator safety measures."

HSE Safety Alerts and Inspections
Ian Clews is not alone in his views on the need to improve the safety of hand-fed platen presses. In the UK, the Health & Safety Executive (HSE) has recently issued safety alerts to users of hand-fed platen presses. It is estimated that in the UK alone, there are between 1,000 and 2,000 such presses that require safety upgrades, mostly operated by companies in the printing and packaging industries. Most of the high-risk machines fall into the 1.4m to 2m-width range.

The HSE is currently considering issuing alerts to users in order to raise awareness of the potential dangers of whole body access between the platens of these machines when operating in the 'dwell' mode. The alerts are in response to two fatalities since 2008 in the UK, where operators were crushed between the platens as they intervened during normal production. In both cases, the hand-fed machine was being used in the dwell mode and the power to the platen was not isolated before the intervention occurred and so the safety devices fitted to the machine did not prevent the platens closing on the operator.

"During the setting process, waste removal, replacement of lay stops or mis-feed retrieval, even with the most safety conscious operators may try to beat the dwell and climb onto the platen press bed or lean into the machine. Whilst between the fixed and moving platen beds the operator is not detected by any of the usual safety systems," explains Ian Clews.

According to the HSE, the latest hand-fed platen presses are much larger than their predecessors and many users now use the machine's dwell mode to either give them more production flexibility or to speed up the machine's output, as this mode can often double the speed of operation. On most hand-fed platen presses, climbing onto the platen from the normal operating position in front of the machine can be done without operating the safe edge that is normally fitted to the leading edge of the lower platen. This means that if a safe system of work is not followed, including isolating the machine, the platen may then continue to cycle if it is being used in the dwell mode and the protective devices will not automatically be triggered.

Further investigation by the HSE has showed that standards of guarding and working practices on many existing, larger hand-fed platen presses need to be improved significantly. HSE has announced that it will commence on-site inspections of hand-fed platen presses in October 2010.

In his presentation to a group of machinery safety suppliers at the HSE's Birmingham offices on 12^th July 2010, Tim Small, HM Principal Inspector at the HSE, stated:  "The HSE deems hand-fed platen presses as high risk machines. Enforcement action will be taken against any UK firms that aren't taking appropriate action to meet these new safety expectations."

Employee Safety-Driven Approach
In November 2009, SCA Display UK decided to improve the safety of its hand-fed platen press at Shenstone to better protect employees. Ian Clews contacted Pilz Automation Technology to discuss possible safety solutions. "By this time, I had already devised several concepts for upgrading the safety of the platen press, but needed to talk to a machinery safety specialist supplier such as Pilz about how the solution could be realised from a technological viewpoint. I also wanted the solution to be modular, enabling a best option for employee protection rather than a cost option. It was critical that we worked with a supplier that had in-depth knowledge of current machinery safety legislation and standards, but with the ability to then apply that knowledge to developing the most appropriate safety system for our machine," says Ian Clews…../Continued on the next page.