Harmonized safety standards bring continuity and clarity to robot use

Recently the International Standards Organization and the Robotics Industry Association in the U.S. harmonized their robot safety standards. Now ISO10218 and ANSI/RIA15.06 are, for all intents and purposes, the same document with minor country-specific deviations.

Canada will soon follow suit with Z434-13, which is out for public review at the time of writing and follows a similar path. This will be an industry first to have a C level or machinery specific standard that will be globally harmonized.

This new standard is a merger of ISO10218-1 (for robot makers) and ISO10218-2 (for the user or integrator). Some major changes have taken place and some editorial changes were made. Since U.S. English and British English are slightly different, the first order of the day was to agree on new terms. The more significant changes to language are:
• Envelope is now space (restricted, operating and safeguarded)
• Reduced speed is now slow speed
• Safety stop is now protective stop (no change to emergency stop)

Functional safety

The first major change is replacement of “control reliability” of the safety systems with Performance Levels (written as PL) and Safety Integrity Levels (written as SIL). The internationally agreed upon benchmark has now changed from Category 3 (or 4) to PL d or e respectively.

The new minimum is called out as being PL d with a structure category 3, as described by ISO13849-1:2006, or SIL 2 with a hardware fault tolerance of 1, as described by IEC62061.

Safe motion

Next up is the (safe) control of robot motion; these functions are generally called collaborative operations. The new ANSI/RIA15.06-2012 defines four kinds of collaborative working: safety-rated monitored stop, hand guiding, speed and separation monitoring and, lastly, power and force limiting. For example, new robots today have safety stopping inputs and safety rated soft limiting capability. This has led to not requiring mandatory hard limits, but it is important to understand that this applies to new robots only.

Risk assessments and validations

Last but not least, the scope of the new standards will require a Risk Assessment and Validation of the safety systems. This requirement will be new for the U.S. market and other parts of Canada, but is not something new to the Ontario market as a result of prestart health and safety reviews.

The overall methodology is not specified within the robot standard but general guidelines are given. Other standards are referenced for this purpose (e.g. IS0 12100, ANSI B11.0) as well as company-specific standards for risk assessments.

Ian Brough is a Certified Safety Applications Specialist with SICK Inc. Reach him at www.sickusa.com.

This column originally appeared in the September 2013 issue of Manufacturing AUTOMATION.