UL Certifies Industrial Devices’ Safety

Thursday, March 31, 2011 @ 02:03 PM gHale

By Nicholas Sheble
Underwriters Laboratory (UL) is pushing its safety oversight of products and processes to the manufacturing and industrial stage.

Along those lines, UL staged a web conference Wednesday with Siemens regarding UL’s “Functional Safety Mark Program.”

Knowing products are safe and ready to go out of the box is more important today than ever. That is where the UL program comes into play. Machine builders, system integrators, and end users need to know if a component underwent evaluation for functional safety characteristics. They also need to know if the integrity of the system’s safety level will remain once they integrate the component into the system.

Functional Safety (FS) is part of the overall safety of a system or piece of equipment that depends on the system or equipment operating correctly in response to inputs.

FS would include the safe management of likely operator errors, hardware failures, and environmental changes.

Some products UL evaluates for functional safety include:
• Burner management systems
• Combustion controls
• Electro sensitive equipment such as laser scanners, light curtains and machine vision equipment
• Elevator components
• Gas detection equipment
• Motor drives
• Process control equipment
• Programmable components
• Programmable logic controllers (PLCs) and programmable automation controllers (PACs)
• Robotics and accessories

Functional Safety exists when every specified safety function takes place and the level of performance necessary for each safety function is satisfactory.

Normally the process includes these minimum steps:
1. Identifying what the required safety functions are. This means engineering has to know with certainty the hazards and the safety functions. A process of function reviews is necessary to identify these.
2. An assessment of the risk-reduction required by the safety function is necessary. This will involve a Safety Integrity Level (SIL) Assessment. A Safety Integrity Level (SIL) applies to an end-to-end safety function of the safety-related system, not just to a component or part of the system.
3. Making sure the safety function performs to the design intent, including under conditions of incorrect operator input and failure modes. This will involve having the design and lifecycle managed by qualified and competent engineers carrying out processes according to recognized functional safety standard. In Europe, that standard is IEC EN 61508, or one of the industry specific standards derived from IEC EN 61508.
4. Making sure and verifying the system meets the assigned SIL, by determining the Mean Time between Failures and the Safe Failure Fraction (SFF). The unsafe failure fraction is the probability of the system failing in a dangerous (or critical) state, derived from a Failure Mode and Effects Analysis or (Failure Mode, Effects, and Criticality Analysis) of the system (FMEA or FMECA).
5. There must be a Functional Safety management audit. The safety-lifecycle management audit is a mechanism used to help reduce systematic problems from appearing in the design of a product.

UL evaluates safety-related products to a variety of standards including:
EN 954 – Safety of machinery and safety-related parts of control systems
IEC 61496 – Evaluation of safety-related electro sensitive protective equipment
IEC 61508 – Functional safety of products, components, and systems: Evaluation covers electrical/electronic/ programmable electronic (E/E/PE) safety-related systems and assessment of the proper safety integrity levels (SILs) of your product or system
IEC 61511 – Safety for instrumented systems for the process industry sector
IEC 61800-5-2 – Safety of adjustable speed electrical power drive systems
IEC 62061 – Safety of machinery and functional safety of safety-related electrical, electronic, and programmable electronic control systems
ISO 10218 – Safety requirements for robots used in industrial environments
ISO 13849 – Safety of machinery and safety-related parts of control systems
UL 1998 – Assessment of software safety and evaluation of computer/software-controlled products
UL 991 – Assessment of controls that employ solid-state devices and are intended for specified safety related protective functions

Kevin Connelly, Industry Manager, Power & Controls, Functional Safety at UL said the certification process could start at $10-20K and go up from there depending on the complexity of the software and hardware that are part of the device or process.

Click here to learn about the UL Functional Safety Mark Program.

Click here for a white paper on the program.

Nicholas Sheble (nsheble@isssource.com) is a technical writer, engineer, and analyst in Raleigh, NC.