What is the minimum dial arc required on a 2-1/4" gauge?

The minimum dial arc required on a 2-1/4" gauge is 270 degrees because it allows for sufficient visibility and readability of the pressure measurements being taken. A larger dial arc enhances the ability to clearly distinguish between different pressure levels, which is crucial for safe operation in high-pressure boiler systems.

A 270-degree arc provides a broad range of scale that encompasses more pressure values, allowing operators to have a better visual understanding of the pressure state without straining to interpret a more limited arc. This is especially important in environments where accurate pressure readings are vital for safety and operational efficiency.

In contrast, a smaller arc such as 180 degrees or 90 degrees would restrict the range of view, making it more challenging for operators to quickly assess the pressure conditions, potentially leading to hazardous situations. A complete 360-degree dial is unnecessary for practical readings since it would repeat information and could lead to confusion.