Question: Why do some covered tasks in the ASME B31Q standard list a span of control of 1:0? What does that mean?
Answer: Let me first define span of control. It is the maximum number of nonqualified individuals that a qualified individual can direct and observe performing a covered task. For example, locating underground pipelines is a covered task with a 1:1 span of control. This indicates that a qualified individual can direct, monitor, and observe one unqualified individual in performing all aspects of the pipe locating task.
A span of control 1:0 ratio indicates that the task may not be performed by any unqualified individual (even under the direct observation of a qualified individual). These are a few of the covered tasks: joining pipe by heat fusion, electrofusion, compression fittings, and welding. In other words, the individual performing any of these tasks must be operator qualified.
Tip: Operator qualification (OQ) covered task designations and related issues must be written into the company’s OQ program manual. Span of control ratio requirements may be established in accordance with approved methods described in the ASME B31Q standard (e.g., subject matter expert consensus, rational process to determine task importance).