Minnesota Special Engineer Boiler License Practice Exam

The purpose of a siphon or pigtail on a steam boiler is fundamentally to protect the steam gauge from high temperatures that may damage the gauge itself. When steam enters the siphon or pigtail, it condenses into a small amount of water due to the cooler metal of the connection, creating a barrier between the high-temperature steam and the gauge. This prevents direct exposure to the steam's temperature, ensuring that the gauge operates accurately and prolongs its lifespan.

This mechanism is essential because without this protective feature, the high temperature of the steam could lead to faulty readings or even failure of the gauge, compromising system safety and efficiency.