This trail of breadcrumbs has led us back to ISO 13849-1:2006, Safety of Machinery – Safety-Related Parts of Control Systems. This new standard is the basis for the PL and B10d ratings you see on many safety devices today. The ratings are ranked “a” through “e” in increasing risk to the operator, with “e” being the greatest risk. Within this standard, the EN-954 categories for circuit types survive, but are only part of the implementation. More common-sense approaches are allowed, taking into account variables such as mean time to dangerous failure (MTTFd) for devices, monitoring devices for failure, circuit types (cat.1-4), and even those hazards which cannot be guarded without impeding the work to be done (such as PPE, signage, training, etc.). All of these are on the table if the situation supports them. ISO 13849-1:2006 was developed with the support of ANSI, as this organization supplied representative engineers to help with development of this standard. ANSI is a contributing member of ISO standards development and adoption boards.
A few years ago, I was working with an internal integration group for a manufacturing company which had facilities in many domestic and international locations. One of the initiatives I had undertaken was to redevelop procedures for assessing safety hazards on automated equipment.
When you see a talk about safety, your first expectation is probably something on proper PPE, procedures or other aspects of safety that are typical fodder for safety “toolbox talks.” What I’d like to discuss in this post, at least in a very general way, is how to design safety into your process control system.
In the wake of the Deepwater Horizon disaster, alarm management has moved once again into the forefront for many companies as they ask: “What is the best way to keep an operator from missing a key alarm when things start to go wrong? What are the obstacles to having an effective alarm management system?” In my experience, the decision to have, or not have, an alarm is more often cultural than it is based on a good operational analysis of the process. That’s why the alarm rationalization process is so necessary and beneficial. It strips away the cultural, “I want the operator to know about…” and replaces it with, “This is the most important thing the operator has to do.”
You can tell a lot about a company, by taking a quick look at their annual report and website. In today’s economy, it’s the results that count — that’s easy to understand —but leading companies take a more holistic approach to measuring safety. If you can only find results or lagging measures, look elsewhere; the lagging measures are functionally useless when it comes to evaluating a company’s future success. Instead, look for companies that provide results along with proactive or leading measures. When you find one, you’ve likely found a company known for its product or service quality, customer service, productivity and financial success.
Would you stand idly by while a two-year old chews on an electrical cord plugged into a live electrical outlet? Would you watch a relative stand on the top rung of your wobbly wooden ladder to help you hang Christmas lights?