The Challenge of Two-Phase Flow

Entrained gas, which is air or gas bubbles mixed with liquid, has historically posed a major problem for Coriolis mass flowmeters. The presence of gas dampens the natural oscillation of the meter’s measuring tubes. This dampening intensifies as the gas volume fraction (GVF) rises, potentially halting the tube oscillation entirely. When this occurs, the device typically freezes on its last steady reading or enters an error state, thus interrupting effective process monitoring.

How Entrained Gas Management (EGM™) Works

In 2012, KROHNE introduced its Entrained Gas Management (EGM™) technology for the OPTIMASS series of Coriolis flowmeters to overcome the limitations of measuring flow when gas is present.

Instead of failing when gas is introduced, the EGM™ system, which uses powerful control algorithms and high-speed digital signal processing within the MFC 400 signal converter, monitors sensor and driver feedback in real-time. This allows it to make precise, continuous corrections to the tube driver level, maintaining the necessary oscillation frequency.

As a result, the flowmeter can continuously and repeatedly measure both mass flow and density, even when transitioning completely from a pure liquid phase to a gas phase and back again (covering 0% to 100% gas content).

Benefits of EGM™ Technology

KROHNE’s EGM™ offers substantial advantages for process reliability and efficiency:

  • Eliminates Downtime: Ensures uninterrupted measurement, even during challenging two-phase flow conditions such as plant start-ups, shutdowns, or the final stages of tank emptying. The meter operates continuously without stopping or requiring a reset due to gas inclusion.
  • Enhances Process Insight (Transparency): Provides operators with an alert or configurable indication when entrained gas is present. This real-time feedback is crucial for pinpointing transient gas issues and driving improvements in overall process quality.
  • Reduces Capital Costs: The ability of EGM™-equipped meters to accurately handle gas entrainment often minimizes or entirely removes the necessity for large, costly gas separation equipment.
  • Broad Compatibility (Versatility): This technology is integrated across the entire OPTIMASS Coriolis flowmeter portfolio, supporting both straight and bent tube designs.

Industries and Use Cases

EGM™ is highly effective in various sectors where managing two-phase (liquid/gas) flow is a persistent challenge:

  • Food & Beverage: Essential for measuring aerated products (e.g., beer, ice cream, dough), raw milk intake (which frequently contains air), and viscous items like mayonnaise.
  • Chemical: Suitable for demanding applications like processing polyurethane foams, measuring viscous monomers, and safety-focused “push-to-empty” tank processes where gas inevitably enters the line.
  • Oil & Gas: Applied in critical operations such as monitoring drilling fluids, facilitating safe truck loading and offloading, and continuous wellhead monitoring where natural gas entrainment is a factor.