Promass Q 500: Reliable Density Measurement in Dual-Phase Processes
Accurate density measurement is critical in many industrial processes, especially where product quality, blending accuracy or custody transfer depend on precise data. However, when the process involves dual-phase fluids, such as water–oil mixtures, measurement stability becomes significantly more challenging.
The Challenge: Air Bubbles and Unstable Density
Entrained gas, non-homogenized flow and intermittent phase distribution can often lead to density values that fluctuate or behave unpredictably. Endress+Hauser's Promass Q 500, designed specifically for demanding applications involving entrained gas and variable process conditions, has proven to be an exceptional performer in these environments.
One of our customers operating a water–oil transfer system faced persistent density instability. Although Promass Q 500 is engineered for high performance density measurement, the process conditions included entrained air bubbles, non-homogenized flow, and shifting phase fractions. These factors caused the reported density values to fluctuate, making it difficult for the customer to maintain reliable control.
Step-By-Step Optimization
To address the problem, we guided the customer through several advanced configuration tools built into Promass Q 500:
1. Multi-Frequency Technology (MFT)
Promass Q uses dual operating frequencies to better interpret the sensor tube behaviour in aerated or inhomogeneous media. Multi-frequency technology "increases the measuring accuracy in the event of micro bubbles in the medium… viscous heavy oils, gas-saturated media, etc."
This helps mitigate:
- Micro bubbles
- Fine dispersed gas
- Light dual-phase inhomogeneity
2. Gas Fraction Handler (GFH)
GFH mode can be adjusted to detect and compensate for entrained gas by stabilizing readings in real-time thus improving measurement reliability.
3. Medium/Bubble Index Optimization
The Medium Index suite contains three tools that help detect, diagnose and filter the influence of bubbles and dual-phase conditions:
- Inhomogeneous Medium Index: Shows overall scale of two-phase flow (0 = no entrained gas, >10 = very high/slug flow)
- Suspended Bubbles Index: Indicates amount of micro-bubbles (0 = none, 10 = strong bubble presence). Useful for bubble-rich emulsions and gas-saturated liquids.
4. Wet Gas Cutoff Adjustment
We refined the cutoff settings for wet-gas applications, filtering out values influenced by transient gas pockets or phase separation.
5. Oscillation Monitoring
Oscillation amplitude drops when two-phase flow or bubbles disturb the tube, indicating added excitation power needed due to dual phase. These diagnostics help confirm:
- When bubbles enter the meter
- Whether your cutoff settings are appropriate
- When GFH needs to be adjusted
6. One-Point Density Adjustment
A final fine-tuning using the one-point density adjustment allowed the meter to be aligned to a known reference point, ensuring highly accurate and repeatable readings.
The Result
Despite the challenging process conditions, the Promass Q 500 delivered stable density trends, improved repeatability and trustworthy performance. The client now has accurate density and volume measurements. This case demonstrates why it is widely regarded as one of the most capable Coriolis meters for multiphase and aerated fluid applications.
Conclusion
The Promass Q 500 stands out as a robust solution for dual-phase and aerated processes. With its advanced diagnostics and compensation algorithms, it consistently delivers dependable measurement, even when the process itself is unpredictable.