Syphons

Syphons are commonly used in the heating & ventilation industry on hot water or steam lines to protect pressure gauges from the effects of the high temperature. Pressure gauges with brass wetted parts typically are only rated to a maximum of 60C so can not be fitted directly to the process line.

"U" Syphons (also known as Swan Neck Syphons) are used for pressure tappings on the side of the pipe or vessel and "Ring" Syphons (also know as Pig Tail Syphons) where the tapping is located at the top.

When first installed, the syphon should be primed by filling the trap with the process media, on steam applications water should be used.

Please note that maximum pressure and temperature varies depending on the materials of construction and syphon design, please see table below. 

The isolating gauge cock should be mounted between the pressure gauge and the syphon.