Safe Operating Limits Definition

Safe Operating Limits Definition

Documentation of safe operating limits, and an evaluation of the consequences of deviations, is required by OSHA 29 CFR 1910.119(d) to be in compliance with the process safety information requirement of the Process Safety Management (PSM) regulation.

Value beyond compliance. In addition, a systematic evaluation and identification of the normal and safe operating and design envelopes as well as deviations from their upper and lower limits is invaluable in developing or adjusting procedures to:

  • maintain efficient and effective operations,
  • meet environmental restrictions, and
  • ensure process safety.

These limits may include temperature, pressure, flow rate, level and composition, and are often interdependent and correlated, making the process of identifying not only appropriate limits but also appropriate control variables a challenge. Our experience and background in evaluation of overpressure protection and temperature boundaries across numerous processing units and a wide range of unit operations makes Inglenook Engineering well suited for assisting our clients in the:

  • definition of safe operating limits, and
  • the evaluation of deviations from those limits.

It is important to note that the SOL definition loses some value when performed as an ex post facto exercise.  At Inglenook, we believe the SOL definition is best utilized as a baseline document which can inform other, necessary safety studies such as PHAs or relief system design.  There can still be value when performed after installation, if effort is made to use the definition for future improvement, particularly in recognizing nonlinear and/or additive effects, and if the SOL definition is performed based on true operating parameters rather than original design parameters.


Check out our Resource Library, particularly our Fireside Chats blog, for more insights. We have a multi-part blog dealing with Safe Operating Limits:

Use the CONTACT US form to ask specific questions about safe operating limits.