Flowmeter optimises concrete flow

Keller Ground Engineering is using an electromagnetic flowmeter to monitor the flow of fluid concrete in a technique known as continuous flight auger for producing piles for foundations.

A Yokogawa flowmeter is playing a key role in a novel application for one of the world’s leading ground engineering contractors.

Keller Ground Engineering is using the meter to monitor the flow of fluid concrete in a technique known as continuous flight auger (CFA) for producing piles for foundations.

The CFA technique involves boring a hole to the required depth using the corkscrew-shaped auger, and then pumping concrete through the auger’s hollow stem prior to withdrawing it and adding reinforcement.

The system provides a quiet, low-vibration form of piling that is ideal for providing foundation support in built-up or environmentally sensitive areas.

Constant monitoring is essential to the success of the CFA system: if too little concrete is pumped into the bore, the foundation will have insufficient strength; if too much is pumped, there is a chance of wastage and additional costs are incurred.

In order to optimise the delivery of concrete, Keller has developed an in-cab instrumentation system for its CFA rigs. This monitors the movement and position of the auger digging head as well as the rate of flow, amount and pressure of concrete delivered during formation of the pile shaft.

A ruggedised computer system assembled in-house, plus software written by Keller’s engineers, is used to provide a real-time display to the rig operator.

The display shows current values of depth, pressure, flow rate, and total volume pumped, and provides an indication to the operator of the ideal concrete pump speed at any particular instant. A hard-copy printoutprovides a permanent record of each pile constructed to give full assurance of quality.

Measurement of the concrete flow is clearly a key parameter in this process, but there are few flowmeters available that can withstand this particular environment. Early trials using ceramic-lined meters were discontinued when the original manufacturer stopped making the product, and a series of abortive efforts were made using alternative materials including plastics, urethane and rubber.

Eventually, after an Internet search, Keller engineers found a reference to Yokogawa flowmeters being used for concrete flow monitoring during the construction of the Channel Tunnel. They approached Yokogawa’s UK operation at Runcorn, who supplied an Admag AE electromagnetic flowmeter with a ceramic lining. Kelleris now using both 4-inch and 6-inch models on its CFA rigs.

Eventually, Keller Ground Engineering hopes to upgrade its entire UK fleet of Soilmec CM48 CFA rigs with Yokogawa flowmeters.

The Admag AE flowmeter uses Yokogawa’s patented dual-frequency technique for both noise immunity and zero stability, making it suited to applications such as batching, filling and the measurement of pulps and slurries as well as concrete.

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