Why trap and Siphons are needed?
Many industrial processes utilize high-pressure steam for direct heating, performing mechanical work, combustion control, and as a chemical reactant. Measuring the pressure of steam is important both for its end-point use and its generation (in a boiler). One problem with doing this is the relatively high temperature of steam at the pressures common in the industry, which can cause damage to the sensing element of a pressure instrument if directly connected.
So that to create a barrier techniques such as pigtails are used.
Water trap and Pigtail siphons:
To avoid the direct contact of hot steam through the steam pipe a pigtail shaped curve is made at the impulse line to the pressure gauge. where condensed steam (water) will accumulate and act as a liquid barrier to prevent hot steam from reaching the pressure instrument.
The same effect is created when we made a water trap in the line. Water trap is a low spot in the impulse line.
When siphons are installed, it should be filled with water or any other suitable separating liquid.
Used to protect the pressure gauge from the effect of hot pressure media, temperature above 65°C
Used to reduce rapid pressure rise, which can affect the gauge.
Used at the inlet and outlet steam flow measurement of boiler