DIVA Flowmeters

The DIVA flowmeter operates on the well established spring loaded variable area (SLVA) principle, where the area of an annular orifice is continuously varied by a precision shaped moving cone. This cone is free to move axially against the resistance of a spring.

However, unlike other SLVA flowmeters, the DIVA does not rely on the measurement of differential pressure drop across the flowmeter to calculate flow, measuring instead the force caused by the deflection of the cone via a series of extremely high quality strain gauges. The higher the flow of steam the greater the force. This strain is then converted into density compensated mass flowrate and is transmitted via a single loop powered 4 -20 mA and pulsed output. This removes the need for expensive differential pressure transmitters, reducing installation costs and potential problems.

The DIVA has an internal temperature sensor, which provides full density compensation for saturated steam applications.

The DIVA steam flowmeter has a system uncertainty in accordance with EN ISO/IEC 17025, of:

• ± 2% of actual flow to a confidence of 95% (2 standard deviations) over a range of 10% to 100% of maximum rated flow.
• ± 0.2% FSD to a confidence of 95% (2 standard deviations) from 2% to 10% of the maximum rated flow.

As the DIVA is a self-contained unit the uncertainty quoted is for the complete system. Many flowmeters claim a pipeline unit uncertainty but, for the whole system, the individual uncertainty values of any associated equipment, such as DP cells, need to be taken into account.

The turndown of a flowmeter is the ratio of the maximum to minimum flowrate over which it will meet its specified performance, or its operational range. The DIVA flowmeter has a high turndown ratio of up to 50:1, giving an operational range of up to 98% of its maximum flow.