Power-Off Clamping for Safety in Industrial Press MachinesDec 19, 2019
If a large industrial press loses power and the platen comes crashing down it can cause catastrophic damage to the machine, serious injury to the machine operator, and in the worst cases, loss of human life.
For this reason, various governmental standards and regulations have established guidelines and directives to prevent against the damages of a gravity fall due to loss of power to the press. Power-off clamping devices can be designed into new machinery or added to existing machines to guarantee compliance for the safety standards throughout the world.
So, what are these standards and how can they be met?
The Four Major Safety Regulations for Hydraulic, Pneumatic, and Mechanical Power Presses
ANSI B11.2 – 2013 Safety Requirements for Hydraulic and Pneumatic Power Presses
The newly revised standard for press machines, "ANSI B11.3-2012 American National Standard for Machines - Safety Requirements for Power Press Brakes," is available at ansi.org. The requirements of this standard apply to those machines classified as power press brakes (referred to simply as "press brakes"), which are designed and constructed for the specific purpose of bending metal, where the press brake is provided with a plate-type ram and a plate-type bed with provisions for attaching standardized press brake tooling.
ANSI is a private, not-for-profit organization dedicated to supporting the U.S. voluntary standards and conformity assessment system and strengthening its impact, both domestically and internationally.
OSHA Directive CPL 02-01-043 Slide-locks Enforcement Policy, Inspection Procedures and Performance Guidance Criteria
OSHA defines press safety devices as “Slide-Locks”. A slide lock is an energy-isolating device applied to a power-press that engages mechanically to support the maximum anticipated load. All forms of slide locks are intended to address gravity hazards. Directive CPL 02-01-043 addresses slide-locks enforcement policy, inspection procedures and performance guidance criteria is available at OSHA.gov. Technically, there is no other rating for the U.S. apart from OSHA.
Although the CPL is a directive based on safety solutions, they do not spell out exactly what equipment needs to be used. Unlike the European or Canadian directives which take a “product” approach and specify the safety requirements down to the device level, OSHA takes more of a “systems” approach to safety, meaning they describe the measures that must be taken to ensure a safe system. While this offers some flexibility in choosing a safety device, it also places a greater burden on those responsible for ensuring that the chosen safety measures meet OSHA standards.
CSA Z142-02 Power Press Standard (Canada)
The Standards Council of Canada (SCC) is Canada’s national accreditation body responsible for the development and application of standards publications that establish accepted practices, technical requirements and terminologies for products, services and systems. The requirements of the CSA Z140-02 Power Press Standard apply to the design, manufacturing, installation, maintenance, and operation of power presses. CSA Z142-02 covers the occupational health and safety requirements for all classes of power presses that are fitted with a ram (plunger or slide) and dies for the purpose of blanking, cutting, trimming, drawing, punching, forming (bending), stamping, assembling, or processing metal and other materials and is available at scc.ca.
DIN EN ISO 16092-3 Safety Requirements for Hydraulic Presses (Germany)
DIN represents German interests within ISO, the International Organization for Standardization. The ISO is a non-governmental body consisting of over 160 countries. They are responsible for developing standards for various industries which promote quality, safety, and efficiency.
The requirements of ISO 16092-3:2017 apply to machine tools safety for hydraulic presses ranging in size from small high-speed machines with a single operator producing small workpieces to large relatively slow-speed machines with several operators and large complex workpieces and can be found at ISO.org or Din.de
A Systems Approach Versus a Product Approach to Press Machine Safety Standards
Today, in the U.S., most modern hydraulic and pneumatic presses have a variety of OSHA-mandated protection systems in place to ensure operator safety. Guards, interlocks, electro-sensitive and opto-electronic devices, emergency stop devices, and other redundant systems have helped make presses safer in recent years. But when it comes to safeguarding the presses themselves from expensive damage to the press or dies, standards in the U.S. fall short of their European CEN counterpart, which uses a product over a systems approach.
In Canada and throughout Europe, a safety catcher is a mandatory device. The primary advantage of the safety catcher over other safety methods, is that it will engage and prevent a crash anywhere in the travel stroke of the platen. A blocking device, such as slide-lock solutions that work by blocking the sliding platen with a swinging device or ram block or by preventing the platen from crashing down, can only prevent a crash when the platen is located above the blocking component.
Rod Locks Versus Safety Catchers
Rod Locks function similarly to safety catchers and can certainly make a press safer than they would be without a power-off clamping device, but rod locks differ from safety catchers in both form and function. Functionally, the purpose of a rod lock is not to catch the platen during a gravity fall condition, but to position and hold the load in a precise location. The primary reason a rod lock is not considered a safety device can be summed up in one word: springs.
Unlike rod locks, where springs create the holding force, with the safety catcher the load itself creates the holding force so it is self-intensifying…no springs to wear or break. Instead safety catchers utilize a tapered clamping system where the clamping force increases as the load increases.
Although it is unlikely that the internal springs of a rod lock would fail, it is possible. If the springs were to fail inside a rod locking unit, the unit could lose holding force which would leave the press susceptible to a crash in the case of a gravity fall.
Rod locks can certainly make your system safer, but technically, they aren’t a true safety device. Safety catchers are the clear and convenient solution for safety compliance throughout the globe. Presses equipped with safety catchers are guaranteed to protect against injury, liability, and loss.
How to be Certain Your Press Machines are Meet the Standards for ANSI, OSHA Directive CPL, CSA ZH2.02, and DIN 6391
Press machines have so much room for failure if not cared for or operated properly, or if a preparation step is skipped. With a heavy ram under a high amount of pressure and no failsafe, the chance of catching a body part in the press may be higher than you'd assume. That is why ensuring a compliant solution for industrial presses is a big part of what we do.
Though U.S. safety regulations offer some flexibility for meeting OSHA standards, we believe safety catchers are the clear and convenient solution for safety compliance, not just in the U.S. but throughout the globe. As the exclusive partner of SitemaⓇ since 1992, we at AME have done our due diligence. Not only have we have we successfully implemented thousands of SitemaⓇ safety catchers in press applications throughout North America, but we have had SitemaⓇ safety catchers evaluated according to OSHA Directive CPL 02-01-043. OSHA has determined that the SitemaⓇ Safety catcher meets all of the requirements of the directive.
We hope this post helps answer the most frequently asked questions about press safety regulations, but we know when it comes to safety compliance the devil is in the details. That’s why our experts are available to assist you with the implementation of the ideal press safety device to meet all your press safety needs. Please contact one of our factory representatives for a custom solution today.