A Van Stone flange is fitted ___________ on a pipe:

A Van Stone flange is designed to be fitted loosely on a pipe to allow for ease of alignment and connection. The loose fit is intentional to accommodate any adjustments needed during installation and to facilitate the attachment of the flange to other fittings or components. This type of flange often allows for slight variations in pipe dimensions and helps in achieving a proper seal when clamped in place.

The other options do not accurately reflect the nature of Van Stone flanges or their typical installation process. For instance, evenly spaced set screws are used in types of fittings that require a more secure attachment, which is not the case here. Similarly, coarsely threaded connections would not provide the necessary flexibility and adaptability that a Van Stone flange requires. Tack welding, while it may provide a temporary hold, is not the standard practice for securing these flanges, as it could hinder future disassembly and maintenance.