Process Analyzer System Safety and Ergonomics, Part I

This article is the sixth in series running in Control over the past several months.

By Gary D. Nichols

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Additional Analyzer Shelter Safety and Ergonomic Concerns

Other safety and ergonomic issues around analyzer shelters and systems that should be considered systems include:

  • Equipment and connection labeling,
  • Proximity to or inclusion of a safety shower and eyewash fountain,
  • Storage of chemical reagents for analyzer systems,
  • Inclusion of a counter and/or sink for preparing analyzer system reagents,
  • Inclusion of a desk or document storage area,
  • Inclusion of a floor drain to storm or process sewers to accommodate chemical spills, general cleaning and mud- or snow-caked boots and shoes,
  • Placement of analyzer systems and other equipment and devices in the analyzer shelter to permit access from front, back and both sides.

Including a desk or reagent handling and preparation area may cause the shelter to be categorized as “normally occupied,” thus necessitating additional safety and ergonomic features.

Lockout and Tagout

The Occupational Safety and Health Act (OSHA), cited in 29 CFR 1910, requires lockout and tagout of mechanical, electrical and chemical energy at key locations where not doing so could endanger the safety and health of workers performing maintenance and service on the equipment. For an analyzer shelter such as the one under discussion in this article, the lockout/tagout points include, but are not limited to, process line sample valves, utility line valves and electrical switches. The lockout/tagout points should be sufficiently close physically and topologically in the system branches, so that the analyzer shelter or individual devices can be isolated without affecting other control or process equipment.

Analytical Gases

Most analyzer systems require cylinder gases in individual cylinders or cylinder banks. Therefore, analyzer shelters should be sited at grade next to a truck-accessible roadway, so that the lifting device on the delivery truck can do most of the loading, unloading and moving work. When the analyzer shelter cannot be adjacent to a roadway, a concrete path between the roadway and the analyzer shelter is needed to minimize manual work when changing gas cylinders; the side of the analyzer shelter for the gas cylinders should face the roadway.

When the analyzer shelter must be above grade, gas cylinder storage, connections and manifolds should be at grade as close as possible beneath the analyzer shelter. A reinforced fiber-glass or metal grating between the concrete and the bottom of the cylinder is recommended to reduce cylinder corrosion, but cylinder storage should be at grade, even if the analyzer shelter is elevated a few inches above grade.

Utility gases and cylinder gases entering the analyzer shelter should be equipped with flow-limiting devices to prevent the house from becoming filled with the gas in the event of regulator failure. Gas manifolds may be equipped with automatic cylinder switchover devices so that gas flow is never interrupted; an alarm or telltale is activated after a switch over to alert the technician that a cylinder needs changing.

Users should always comply with the latest appropriate national, state and local codes, industry standards and practices, and corporate and site standards and practices before designing, engineering, constructing and operating these types of equipment.

In the next article, we shall discuss the safety and ergonomic design and construction of analyzer sample handling systems (SHS), personal ergonomics, constructability and designing, training and documenting for ongoing maintenance safety and ergonomics.

For additional reading on these issues, see the following publications:

  • Gruhn, Paul, PE and Harry L. Cheddie, PE, Safety Shutdown Systems: Design, Analysis and Justification, ISA, 1998.
  • “National Electrical Code,” National Fire Protection Association (NFPA), Quincy, Mass.
  • NFPA 496, Standard for Purged and Pressurized Enclosures for Electrical Equipment, National Fire Protection Association (NFPA), Quincy, Mass., 2003.
  • NFPA 497, Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, National Fire Protection Association (NFPA), Quincy, Mass., 2004.
  • U.S. Department of Labor, Occupational Safety and Health Administration, Code of Federal Regulations, 29 CFR 1910.

This article is the sixth in series running in Control over the past several months. Here are links to all of them in the order of their appearance.

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