How are steam pressure gauges protected from high temperature of steam?

Steam pressure gauges are protected from the high temperature of steam through the use of siphon tubes. A siphon tube, also known as a siphon or steam siphon, is a U-shaped pipe that is installed between the steam source and the gauge. It serves to cool the steam before it reaches the gauge.

The structure of the siphon tube allows steam to condense into water within the tube, which acts as a barrier. This condensate prevents the high-temperature steam from directly contacting the pressure-sensing element of the gauge. As a result, the gauge can provide accurate readings without being damaged by excessive heat. This is a critical component in ensuring the longevity and reliability of the pressure gauge in systems handling steam.

In contrast, the other options do not serve the purpose of protecting gauges from high steam temperatures. Welded flanges are used to connect pipes or equipment but do not provide thermal protection. Heat exchangers are designed to transfer heat between fluids, and nubs are not relevant in the context of steam pressure gauge protection.