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.
Applications:
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Used to protect the pressure gauge from the effect of hot pressure media, temperature above 65°C
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Used to reduce rapid pressure rise, which can affect the gauge.
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Used at the inlet and outlet steam flow measurement of boiler