Instrument Gauge Tubes - Siphon Tubes

A pressure gauge siphon tube, also known as a pressure gauge pigtail, is a device installed to protect the gauge from high temperatures. Siphons are used in hot vapor applications and are particularly common on steam systems.

These systems are important for monitoring vapor pressure for end-point use and generation in kettles. However, a problem arises because the high steam temperature at typical industrial pressures can damage the pressure sensor if connected directly.

 

1.     Types of Siphon tubes:

1.1       U-Tube Siphon

• Function: U-tube siphon tubes are shaped like a 'U' and are designed to trap condensate, creating a barrier between the hot steam and the pressure gauge.
• Pros: Good at preventing high-temperature steam from reaching the pressure instrument. Compact and straightforward design.
• Cons: Might not provide as much cooling as coil siphon tubes.
• Applications: Typically used in steam heating systems, boiler systems, and various industrial applications where space is limited.

1.2       Coil Siphon Tube

o   Function: Coil siphon tubes are wound into a helical or spiral shape. They allow the steam or hot fluid to cool down before reaching the pressure gauge or sensor.

o   Pros: Effective at cooling the fluid, preventing damage to the instrument. Suitable for high-temperature applications.

o   Cons: Can be bulky and require more space for installation.

o   Applications: Used in steam boilers, industrial steam systems, and high-temperature chemical processes.

1.3       Pigtail Siphon Tube

o   Function: Pigtail siphon tubes are shaped like a loop or pig’s tail. They trap condensate, which acts as a barrier between the hot steam and the pressure gauge.

o   Pros: Compact and easy to install. Effective in protecting gauges from high-temperature steam.

o   Cons: Less cooling capability compared to coil siphons.

o   Applications: Commonly used in steam heating systems, boilers, and other steam-driven equipment.

 

2.     Functions of Siphon Tubes

• Protection: Siphon tubes protect pressure instruments from high-temperature steam or fluids by cooling them down or creating a condensate barrier.
• Pressure Measurement: They enable accurate pressure measurement by preventing direct contact of high-temperature fluids with the sensing element.
• Safety: Siphon tubes enhance safety by preventing damage to sensitive instruments, which could lead to system failures.

3.     Pros and Cons of Siphon Tubes

• Pros:
• Temperature Control: They effectively reduce the temperature of steam or hot fluids before they reach pressure gauges.
• Instrument Protection: They prevent damage to pressure instruments, extending their lifespan.
• Safety: They contribute to the safe operation of industrial systems by maintaining the integrity of pressure measurements.
• Cons:
• Space Requirements: Some types, like coil siphon tubes, require more space for installation.
• Maintenance: Siphon tubes may need regular maintenance to ensure they are free from blockages or buildup.
• Cooling Limitations: Straight siphon tubes offer limited cooling, making them unsuitable for very high-temperature applications.

4.     Applications

• Steam Boilers: Siphon tubes are widely used in steam boilers to protect pressure gauges from direct contact with high-temperature steam.
• Industrial Steam Systems: They are employed in various industrial steam systems to ensure accurate pressure measurements and instrument protection.
• Chemical Processes: In chemical industries, siphon tubes protect instruments from high-temperature chemical reactants.
• Heating Systems: Used in steam heating systems to safeguard pressure instruments from hot steam.

By using siphon tubes, industries can ensure the reliable and safe operation of their pressure measurement instruments in high-temperature environments.