What is the allowable deflection of 1.5" steel pipe based on the length of span?

The allowable deflection for structures, including 1.5" steel pipe, is commonly determined by industry standards to ensure safety and structural integrity. In this context, the correct answer reflects the guideline for allowable deflection, which is defined as the length of the span divided by a certain factor.

A factor of 180 is often used for deflection limits in structural applications, particularly for materials like steel. This means that the maximum allowable deflection of the steel pipe should not exceed the length of the span divided by 180. For instance, if the span were 1800 mm, the maximum allowable deflection would be 10 mm. This limits the sagging that could occur under load, ensuring that the pipe remains within safe operational parameters and does not compromise the structural integrity of the installation.

Other factors mentioned in the options represent more restrictive or less common limitations in different contexts, but the most widely accepted standard for this specific material and usage falls under the 180 factor. This ensures a balance between safety and material efficiency in theatre rigging applications.