There are times when it must be possible to measure the pressure of a pipe that circulates steam. The pressure gauges measure the steam pressure, but these pressure gauges must be safe from the heat and pressure surges of the circuit itself. This is where syphons (pigtail or U-shaped) come in. Syphons or pigtail syphons are looped pipes placed in the pipe before a pressure gauge to protect it from pressure surges or other problems caused by heat. Syphons help dissipate heat from a tube and protect instrumentation.