Flow measurement on a cutter suction dredger

The operator of a dredging fleet in Egypt specialises in the construction and maintenance of canals, ports and other waterways. It also utilises cutter suction dredgers (CSD), which are considered one of the most effective types of dredging vessels. CSD feature rotating cutter heads and large pumps to remove sediment from a sea or riverbed to transport it into storage tanks on board.

Process efficiency and the ability to record the amount of material moved are crucial in dredging operations. A key factor here is the flow velocity of the dredged material, which must be kept within a defined optimum range to prevent clogging, excessive wear and tear of equipment and piping, or pump cavitation. Controlling flow velocity and volume requires reliable and accurate flow measurement of the dredging slurry.

The operator was therefore looking for a heavy-duty flowmeter capable of accurately measuring the flow velocity and volume of the medium to maintain the highest dredging efficiency. Since production speed is high and the dredging slurry is an extremely abrasive mixture of water, sand, rocks, and occasionally sharp unknown particles, only flowmeters with a proven track record in dredging applications were taken into account. For this project, the customer specified an electromagnetic flowmeter (EMF) as the preferred solution.

KROHNE’s OPTIFLUX 4300 flowmeter proved to be the perfect match for this dredging application. The EMF has long since established itself as the preferred flowmeter for leading companies within the dredging industry. It was supplied in a special design for dredging applications, featuring a liner with extremely robust and abrasion-resistant ceramic tiles and a protective hard steel inlet and outlet ring to provide a high degree of durability at the flange connections. The full-bore flowmeter has no intruding or rotating parts that could be damaged by the slurry. It is further equipped with rugged, flush-mounted “low-noise” electrodes designed for slurries with very high solid content to ensure stable and reliable measurement.

The electronics of the mag meter feature a wide range of diagnostics to monitor the meter health and support long-term stability. The flowmeter is always specifically calibrated for dredging applications and their flow velocities. It holds all the important marine type approvals relevant to the dredging industry.

RMS, KROHNE’s sales and service partner in Egypt, installed and commissioned the flowmeter in the customer's DN1000 (~44”) suction pipe onboard the dredger. The customer's performance requirements were met immediately, despite the pipe being a descending vertical one with downward flow, which can be challenging and requires controlled back pressure.

The OPTIFLUX 4300 provides accurate, real-time measurement, enabling the dredging company to keep dredging velocity constantly within the optimal range of 3…4.5 m/s. This ensures a well-balanced process, preventing clogging and costly interruptions due to flow velocities that are too low, while also preventing excessive pipe wear and unnecessary energy costs caused by flow velocities that are too high. By continuously monitoring flow velocity and volume flow directly in the dredge control room, the customer can run the dredging process at maximum efficiency, while keeping maintenance costs and operational expenditure (OPEX) low.

The OPTIFLUX 4300 has established itself as the mag meter of choice for the demanding conditions of dredging. Specifically engineered for measuring the flow of liquids with very high solid content, the OPTIFLUX 4300 offers unparalleled durability in applications involving highly abrasive slurries. Compared to conventional EMF, the KROHNE meter’s unique ceramic tile design boasts reduced wear, maintenance interventions and downtime. This installation adds up to the flowmeter’s long track record in dredging applications worldwide.