When specifying a sensor for an application, you can't just pick a product out of a catalog. A number of factors must be considered before you're ready to purchase a device. One area often forgotten is safety. The substance of these requirements comes from several sources—corporate standards; federal, state, and local mandates; and broadly accepted engineering guidelines, such as those provided by ISA. If you don't appreciate the imperatives of safety considerations, just wait. You will.
A Checklist for Success
Items sometimes overlooked by a new staff member when constructing a sensor specification are the corporate safety and power requirements for any system installed in an operation. Be sure the equipment you specify meets these demands. You may have to contact the corporate engineering and/or the safety group to find the related documents. ISA has contributed greatly to safety standards and sells many of them on their Web site.
The chemical industry also publishes a huge amount of safety information, some of which you may need to know about in detail, depending on the product you are measuring and the potential hazards your sensing system may introduce into a facility. Check out Interactive Learning Paradigms' 100 free Web resources on material safety data sheets.
If your sensor is to be installed in a location where flammable liquids and/or gases are present or could be present, you should review your preliminary specs with the local safety officer. You may need special isolation devices for your sensor or its support items, but you should have identified them already. They belong in your spec, too.
Additionally, if your sensor contains radioactive materials or potentially hazardous chemicals, the safety and/or nuclear safety officer will want to know about it. He or she can advise you about posting proper warnings and notices, special labeling, and action plans for proper disposal of any portion of sensitive items removed from the installation. Radioactive items require special handling and are required by law to be inventoried at several levels. The Nuclear Regulatory Commission maintains control over medical and industrial radioisotopes.
An engineer I knew actually found a radioactive thickness gauge in a trash bin at a facility where we worked. It was part of an obsolete instrument that was to be scrapped. No one had told the janitor about proper disposal procedures. Aside from the possible hazard to third parties, the company could have been subject to a significant fine from state and federal nuclear regulatory agencies.
Safety requirements are sometimes overshadowed by such issues as performance and cost. But a complete sensor specification includes all manner of safety requirements. It's better to be right the first time than to have to go back and fix it latter.