Which device is used when connecting instrumentation to a steam boiler to prevent backflow?

Which device is used when connecting instrumentation to a steam boiler to prevent backflow?

• A. Anti siphon device
• B. Relief valve
• C. Isolation valve
• D. Check valve

Answer: (A)

Preventing siphon backflow in instrument connections to a steam boiler. When you attach gauges, sensors, or sampling lines, a siphon effect can pull boiler water back into the instrument line if pressures change. An anti-siphon device breaks that path, often by providing an air gap or vented path, so the instrumentation stays isolated from boiler fluids and readings remain accurate. Relief valves are for venting excess pressure, not backflow prevention. Isolation valves can shut off a line but don’t stop siphoning when flow or pressure reverses. A check valve does block backflow, but for instrumentation lines in steam systems, the anti-siphon device is the purpose-built solution to prevent backflow and protect the instruments.

Preventing siphon backflow in instrument connections to a steam boiler. When you attach gauges, sensors, or sampling lines, a siphon effect can pull boiler water back into the instrument line if pressures change. An anti-siphon device breaks that path, often by providing an air gap or vented path, so the instrumentation stays isolated from boiler fluids and readings remain accurate.

Relief valves are for venting excess pressure, not backflow prevention. Isolation valves can shut off a line but don’t stop siphoning when flow or pressure reverses. A check valve does block backflow, but for instrumentation lines in steam systems, the anti-siphon device is the purpose-built solution to prevent backflow and protect the instruments.