A pigtail siphon, also known simply as a pigtail, is a type of siphon tube commonly used in industrial piping systems to protect pressure instruments, such as pressure gauges, pressure transmitters, and pressure switches, from the effects of high temperatures or the presence of corrosive or viscous fluids.
The pigtail siphon consists of a coiled or U-shaped tube, typically made of metal (such as stainless steel), that is attached to the inlet of the pressure instrument. The tube is usually filled with a fluid, such as water, which acts as a thermal barrier or heat sink.
The primary purpose of a pigtail siphon is to isolate the pressure instrument from direct contact with the process fluid, which may be at elevated temperatures or contain corrosive substances. By routing the process fluid through the coiled or U-shaped tube, the pigtail siphon allows the fluid to cool down or condense before reaching the pressure instrument.
Key functions and uses of a pigtail siphon include:
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Temperature Protection: Pigtail siphons are used to protect pressure instruments from exposure to high temperatures in the process fluid. The coiled or U-shaped design allows the fluid to cool down as it travels through the tube, preventing overheating of the pressure instrument.
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Condensation Prevention: In steam or vapor applications, pigtail siphons help prevent condensation from entering the pressure instrument. The coiled or U-shaped design allows any condensate to collect at the bottom of the tube, preventing it from reaching the pressure instrument.
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Pressure Equalization: Pigtail siphons can help equalize pressure fluctuations or pulsations in the process fluid before they reach the pressure instrument. The coiled or U-shaped tube acts as a damping mechanism, smoothing out pressure variations.
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Fluid Separation: In applications where the process fluid contains solid particles or contaminants, pigtail siphons can help separate these substances from the pressure instrument. The coiled or U-shaped design allows any debris to settle at the bottom of the tube, preventing it from reaching the pressure instrument.
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Corrosion Resistance: Pigtail siphons are often made of corrosion-resistant materials, such as stainless steel, to withstand exposure to corrosive process fluids. They help extend the lifespan of pressure instruments by protecting them from corrosion damage.
Overall, pigtail siphons play a crucial role in ensuring the reliability and longevity of pressure instruments in industrial environments where high temperatures, corrosive fluids, or pressure fluctuations are present. They provide a simple and effective solution for isolating pressure instruments from harsh process conditions while maintaining accurate pressure measurements.
