Pressure measurement for high-pressure reactors: In an ammonia reactor operating at elevated pressure, which instrument is typically used for direct pressure indication?

Introduction / Context:
Ammonia synthesis reactors run at high pressures (tens to hundreds of bar). Selecting an appropriate pressure instrument depends on the pressure regime and robustness needs in hazardous, high-temperature environments.

Given Data / Assumptions:

• Process pressure far above atmospheric.
• Need for rugged, on-skid indication and compatibility with industrial conditions.
• Vacuum-level accuracy is not the requirement.

Concept / Approach:
The Bourdon gauge converts internal pressure into elastic deformation of a curved metallic tube, which is translated to pointer motion. It is the standard choice for medium to very high pressures in industrial service. Manometers are best for low to moderate pressures and lab settings; vacuum gauges (Pirani, McLeod) are specialized for low pressures, not high-pressure reactors.

Step-by-Step Solution:

Verification / Alternative check:
Plant P&IDs commonly show Bourdon-type gauges and transmitters (with diaphragm seals) on high-pressure ammonia loops.

Why Other Options Are Wrong:

• U-tube/Inclined manometers: Bulky, fragile, suited to low differential pressures.
• Pirani/McLeod: Vacuum measurement devices, not applicable at high pressure.

Common Pitfalls:
Choosing vacuum instruments by mistake due to familiarity with lab equipment; reactor services demand rugged industrial devices.

Final Answer:
Bourdon gauge