Machine & Operator Safety
Pressing safety-standard updates: Changes to CSA Z142 power-press guidelines
November 26, 2009 By Cory Newton
Five years ago, when the CSA Z142-02 power-press standard was first published, it was a major improvement on its predecessor. More stringent requirements for controls and safety devices were established, and it offered the first attempt at harmonization with other standards at the time, such as ANSI B11.1, RIA 1506 and EN693. Afterward, both the CSA Z434 for industrial robots and robot systems and CSA Z432 for machinery safeguarding adopted these same requirements.
As part of the CSA Standard process, standards are always being reviewed. During the five-year review process, a technical committee was assembled to determine if the current edition was still relevant and to assess whether there were any new technologies that would necessitate amending the document. It was then decided the standard would be updated to recognize new issues and maintain the existing technical requirements.
One of the first issues the committee faced was a coroner’s inquest into the death of an employee in Kitchener, Ont., during the maintenance of a power press. The inquest’s recommendation was for the CSA Technical Committee on Power Press Operation to develop maintenance safety requirements for the proper and safe removal of hydraulic tie rod nuts, because if the pressure on these nuts is released incorrectly, maintenance personnel can be placed at risk — and in this particular case, the error caused the death of a worker. Therefore, an additional technical requirement was added to the new standard: anyone attempting to use hydraulic tie rod nuts to release a press must use the equipment and procedures laid out in the standard.
The second issue the committee dealt with was the introduction of servo or direct-drive presses. Servo presses have been in the metal-forming industry for more than 20 years, but it’s only in the past several years that they have become more common in North America. Not only that, but they are common today in a large portion of new presses being sold, in part because of their flexibility, accuracy and efficiency. Unfortunately, these types of presses use direct and servo-drive technology that is not fully covered in the existing standard. Unlike conventional presses, starting and stopping is directly controlled by the press controllers. There are no valve actuators, so there is a prescriptive requirement on the safety performance level of the controllers. There is also a new requirement for holding brakes to ensure the slide is locked in position when power is removed from the drive controller.
Additionally, the committee looked at laser AOPD guarding devices, which have been commonplace on European press brakes for years but have not been widely used in Canada until the past few years. These laser safeguarding-systems are very flexible and allow the operator to be more productive than light curtains allowed. Unfortunately, under the existing edition of Z142, laser systems are not acceptable primarily because of the safe-distance requirements. The advantages these devices offer operators, and their flexibility in complex forming, make it very important that they be included in order to help Canadians compete in the global marketplace. Not allowing them places Canadian manufacturers at a disadvantage. The challenge facing the technical committee was to keep the intent of the existing ISO Standards for these devices intact while adapting Z142 to meet the needs of Canadian stakeholders. In the end, the committee decided to allow the use of 10-mm-per-second “slow speed” from Europe’s prEN 12622:2006 hydraulic press-brake standard as an acceptable condition for overriding these particular safety devices.
In developing the new standard, Z142 needed to be harmonized with other standards. During this time, the United States’ ANSI B11.1 was also in development, so it was important to ensure consistency with our largest trading partner.
Some items that were added to harmonize with the ANSI B11.1 included the addition of slide-lock requirements and references to issues with large presses previously not addressed. Other changes included the removal of brake monitors as a requirement when not used with safeguarding devices to signal a stop and the removal of RF devices as acceptable electronic safeguarding devices.
A final task by the committee was to try harmonizing with other standards for control performance level. In the previous edition of Z142, the term “control reliable” replaced the previous term “fail safe” as a performance requirement for all safety circuits, devices and safety-related control functions. The committee looked toward the recent ISO 10218 standard for industrial robots for assistance. It was decided the new term would be “safety circuit performance level” and allowed for the use of other standards that have equivalent levels to control reliability. It was not the committee’s intention to increase the performance levels but to allow equipment from other countries to meet requirements in Canada.
The updated version of CSA Z142 has finished the public review stage. The technical committee will be reconvened after the public review period and all comments submitted from industry will be reviewed. Assuming no major issues ensue, the new edition should be published by the end of 2009.
Cory Newton is the president and owner of Tekpress Solutions Ltd., a company specializing in power-press and machine guarding. He is the chair of the Z142 Code for Power Press Operations, the vice-chair of the CSA Z432 Safeguarding of Machinery Standard and a technical committee member of the CSA Z434 Industrial Robots and Robot Systems Standard.