Which of the following conditions is monitored for both safety and operational efficiency in systems?

Monitoring vibration in systems is crucial for both safety and operational efficiency. Excessive vibration can indicate underlying issues such as misalignment, imbalance, wear, or deterioration in machinery components, which can lead to equipment failure if not addressed. Such failures can pose safety risks to personnel and the surrounding environment, making vibration monitoring a key safety measure.

From an operational efficiency standpoint, managing vibration helps maintain optimal performance levels of equipment. High levels of vibration can result in increased wear and tear, more frequent maintenance needs, and reduced lifespan of machinery. By ensuring that vibration levels remain within acceptable limits, operators can enhance reliability and performance, leading to improved overall efficiency and cost-effectiveness in operations.

This focus on vibration monitoring is distinct from the other options. While low viscosity may relate to fluid dynamics, it's not directly tied to both safety and operational efficiency in the same way as vibration. Pressure balance focuses on the stability of pressure in a system but might not serve as a broad indicator of general machinery condition. Flow uniformity is important for certain processes but doesn't encompass the comprehensive monitoring needed to predict equipment failures or safety hazards as vibration does.