Which instrument is used to monitor engine speed during the churn test?

• A. Circulation relief valve
• B. Tachometer
• C. Temperature gauge
• D. Pressure relief valve

Answer: (B)

The churn test relies on confirming the engine is turning at the prescribed speed to ensure the pump operates at the expected performance. The instrument used for this is the tachometer, which directly measures revolutions per minute (RPM) of the engine, giving you a clear readout of whether you’re at the target speed and how rpm may change under load.

Temperature gauges only show heat, not how fast the engine is turning. Pressure relief valves and circulation relief valves are safety components that manage pressure or flow, not speed measurements. So, the tachometer is the essential tool for monitoring engine speed during the churn test.