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Product category: Waste-water handling, monitors + treatment
News Release from: Emerson Process Management - Mobrey Measurement | Subject: MSP900 and MCU902
Edited by the Processingtalk Editorial Team on 22 April 2003

Flow monitoring system saves Beckton STW
GBP20k

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Innovative use of a new differential level monitoring system from Solartron Mobrey has saved Thames Water thousands of pounds on a flow meter refurbishment project at Beckton Sewage Treatment Works

Ultrasonic MSP900 level meters and new dual input MCU902 controllers from Solartron Mobrey are being used to monitor mixed liquor flows to 16 final settlement tanks The system allows re-use of existing pipe-work with no need for large scale rebuilding, or special instrumentation

Serving a population of nearly 3,000,000, Beckton is one of the oldest, and also one of the largest sewage treatment works in Europe.

As part of the on-going refurbishment at the plant, contractor MJ Gleeson was tasked with finding a way of monitoring mixed liquor flows from the aeration lanes, so that Thames Water would be able to balance the flow to sixteen of the final settlement tanks.

The original mechanical flow meters had exceeded their design life and were no longer functional, although all the pipe work was still in situ.

The system consisted of sixteen venturi primary flow elements feeding each of the sixteen final settlement tanks.

The head-loss across each venturi is measured in two vertical stand pipes, the difference in level being indicative of flow.

In the past, this was measured using a mechanical float system with a gauge display, but this part of the system had long since ceased to operate with any degree of accuracy or reliability.

MJ Gleeson, working with Thames Water under the Trident West Alliance, has replaced the maintenance-intensive float system with the new differential ultrasonic level system.

The MSP900s monitor the level in each stand pipe, and the MCU902 calculates the difference in level, and so calculates flow.

The information is used by the operator to adjust the flow to each final settlement tank using a penstock valve, and the system requires virtually no maintenance at all.

Neil Cuthbert Electrical Enginer, MJ Gleeson explains: "The neat thing about this solution is that the MCU902 does the differential calculation automatically.

It is designed for exactly this type of application.

Without it, we would have had to commission custom instrumentation which would have been very much more expensive.

The system saved Thames Water about GBP20,000".

Designed for use with the MSP range of level transmitters, the innovative MCU902 features two inputs for a highly cost effective measurement of the sum or difference of two signals, a common need in the water industry.

It is a compact controller with a built-in display, which is easily programmed to show the required sum or difference data in user-specified units.

A 4-20mA output is provided for direct connection to a PLC or computer control system, and five voltage-free relays are available for alarm and/or screen cleaning/gate control.

The robust, HART compatible unit is suitable for installation in harsh outdoor conditions, and is IS-rated suitable for Zoned applications.

MCU902 is mains powered and has EMC, LV and ATEX approvals.

Beckton operators use the information from the local MCU902 displays on the sixteen controllers to balance the flow to the settlement tanks.

In the future, Thames Water plans to connect the controllers to the site supervisory control and data acquisition (SCADA), system allowing flow data to be logged and supervised from the comfort of the control room.

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