What is the minimum manhole size for elliptical shapes?

The minimum manhole size for elliptical shapes is correctly identified as 280mm x 380mm or 250mm x 410mm. This specification is significant because it ensures adequate space for personnel to enter and exit safely while also allowing for the proper handling of equipment and maintenance tasks within the manhole.

In the context of design and safety standards, elliptical shapes offer certain advantages, such as structural integrity and better flow characteristics in some cases, making the size requirements particularly important. The specified dimensions provide enough clearance for operators and maintenance workers, which is essential for safety in confined spaces. This is particularly true in situations where equipment might need to be maneuvered through the manhole, or where tasks may require additional room to work effectively.

The other options listed, while they do specify sizes, do not meet the minimum requirements outlined for elliptical manholes, which is pivotal in regulatory compliance and operational safety in industrial settings. Understanding these dimensions helps ensure both the safety of individuals working in these environments and the efficient function of the infrastructure involved.