In process instrumentation, steam flow is typically measured in which units?

• A. Bar
• B. Pounds per Hour
• C. Celsius
• D. Gallons per Minute

Answer: (B)

Steam flow is expressed as a mass flow rate, because the amount of energy carried by steam depends on how much mass is moving, independent of its current density. In practice, pounds per hour (lb/h) is the common unit in many process environments (with kilograms per hour used in metric settings). This directly supports energy calculations—total energy transfer is mass flow times the steam’s enthalpy. Volumetric units like gallons per minute would vary with changes in density as pressure and temperature vary, making them less reliable for steam delivery. Bar measures pressure and Celsius measures temperature, neither of which represents how much steam is actually being supplied.