Testing Requirements of Safety Mats

By Joe Lazzara, Scientific Technologies Inc.


Floor mats as a safety device were originally derived from the commercial use of the simple electric doormats. The sole purpose was to trigger the opening of an automatic door to permit hands free entry or exit. These mats were used everywhere from hospitals to grocery stores. In fact, several U.S. manufacturers today still offer safety mats in many sizes with exceedingly odd dimensions derived from, as you probably guessed, the ideal sizes for automatic doormats.

As these commercial mats evolved into industrial safety mats, they began to be referenced in safety standards, such as ANSI B11.19. The notations in the American standards were primarily concerned with the proper installation. There was little regarding the actual construction and testing of the mats. For example, B11.19 vaguely specified that a "safety mat device shall be designed and construction to detect the presence or absence of the operator or others." What it did not provide was any suggestion on how to test or verify this requirement.

In March 1997, the European Committee for Standardization, or CEN, (the letters are derived from the French translation), approved EN1760-1, a new standard directed at the design and testing of pressure sensitive mats. Let’s examine some of the design and testing requirements for a safety mat to meet this standard.

Testing Requirements

Where B11.19 was non-specific, EN1760 excelled in details. The major contribution of the European standard was a comprehensive sensitivity and durability testing specification. Safety mats that meet the stringent requirements of EN1760-1 will display the CE mark and a supporting certification from a European Union authorized, third party test agency.

For example, a safety mat designed for use with persons weighing more than 30 kg must be sensitive enough to detect a test piece 11 mm in diameter with an actuating force of 300 Newtons (67 pounds), a test piece diameter of 80 mm and 300 Newton force, and a 200 mm test piece with a 600 Newton force.

Safety mat operational durability is verified by its ability to function properly after one million operations with a 75 kg mass. A second test employing 100,000 operations at five separate locations on the active area of the mat, for a total of 500,000 operations, is also required. Additionally, the mat must also withstand a static force application of 2,000 Newtons (450 pounds) over a test diameter of 80 mm for a period of 8 hours. A two minute recovery period is allowed, after the force is removed.

Mat Edge Trim

Although EN1760-1 has no specific design test for mat edge trim, it does require that the mat be provided with a means for securing the device in a permanent location. The standard also requires the slope of edge trim shall not exceed 20°, to minimize the risk from tripping. The trim must be identified by a contrasting color or marking.

Multiple Safety Mat Installations

When a safety mat installation involves the use of two or more mats adjoined in a contiguous manner, the joints and junctions must also be active. This is verified using the 80 mm test piece at the joint locations.

Safety Mat Control Unit

EN1760-1 contains some specific requirements for the safety mat controller, such as vibration, electrical shock, power supply, labeling and enclosure requirements. The safety related categories and control systems for the mat controllers are covered under EN954, Safety of Machinery – Safety Related Parts of Control Systems.

It is clear from the EN1760-1 standard that mats and control units are tested together, and are certified to EN1760-1 as a system. It is not possible to maintain the CE certification by using mats and controllers from different manufacturers, unless the individual components are again tested as a complete system.

With the influence of EN1760-1, safety mat systems have evolved from a simple device used to open automatic doors at the supermarket to a sophisticated and rugged means of guarding machinery, complex manufacturing cells and robots. However, the extra testing and durability is only ensured if a mat is independently certified and CE marked to a standard, such as EN1760-1.

I would like to thank all of you for making this column on automation safeguarding a success during 1999. I look forward to next year as we explore further developments in safeguarding techniques, methods and standards. Until next month, be safe out there!

Lazzara on Automation Safeguarding is a monthly column written for Safetyonline.com and Plantautomation.com

Joe Lazzara is president and CEO of Scientific Technologies Inc. (STI, Fremont, CA), the largest provider of automation safeguarding solutions in North America. Lazzara began his career with Hewlett Packard in 1973 where he had responsibility for safety and environmental issues for one of HP’s largest divisions. He joined STI in 1981 as vice president and became president in 1989 and CEO in 1993. Lazzara received a bachelor’s of environmental engineering degree from Purdue University and an MBA from Santa Clara University.