When is a bullseye water sight glass acceptable on a miniature boiler?

A bullseye water sight glass is acceptable on a miniature boiler specifically when there is insufficient space for a gauge glass. This situation arises when the physical limitations of the boiler's design or installation prevent the incorporation of a traditional gauge glass, which is necessary for monitoring water levels in a boiler effectively.

The bullseye sight glass provides a clear view of the water level and is a crucial safety feature that allows operators to check the water level visually without needing additional space for larger gauge glass fittings. In cases where the boiler's size or configuration restricts the standard gauge glass installation, the bullseye alternative still ensures that the operator can assess water levels adequately, thus maintaining operational safety and efficiency in the system.

Choosing this option emphasizes the importance of adapting safety measures to fit the constraints of different boiler designs, ensuring that proper monitoring can still occur even in restricted environments.