Minnesota Boiler License Practice Exam

Each steam gauge connected with a valve must be connected to at least what size siphon?

1. 1/4 inch

2. 1/2 inch

3. 1 inch

4. 3/4 inch

The correct answer is: 1/4 inch

The correct size for a siphon connected to a steam gauge is 1/4 inch. A siphon serves to protect the gauge from high temperatures and pressures by providing a water column barrier that cools the steam before it enters the gauge. A siphon that is too small may not adequately protect the gauge, while larger sizes are generally unnecessary for standard applications. Using a 1/4 inch siphon strikes a balance between sufficient protection and practical installation size. In practice, the sizing must ensure that the water column can effectively stabilize the steam pressure fluctuation, avoiding damaging effects that can lead to inaccurate readings or equipment failure. Larger siphon sizes, such as 1/2 inch or 3/4 inch, may be used in certain high-capacity systems but are not a requirement per standard connection practices for steam gauges. Thus, for typical arrangements, the minimum size of 1/4 inch is considered adequate for the effective operation of the siphon in protecting the steam gauge.