Product category:
Industrial Drives/Controls
News Release from: ABB Automation Tech (Drives and Motors) | Subject: Variable-speed drives
Edited by the Engineeringtalk Editorial
Team on 10 October 2003
Quarry control helps maintain river
levels
ABB drives, controlled by an ultrasonic level controller, are helping maintain the water levels in the Mells River in Somerset.
ABB drives, controlled by an ultrasonic level controller, are helping maintain the water levels in the Mells River in Somerset The equipment is used by Hanson Aggregates to pump water from its limestone quarry near Frome, Somerset, producing 3Mt a year from work levels up to 90m below the water table
This article was originally published on Engineeringtalk on 29 Mar 2004 at 8.00am (UK)
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The water was previously pumped to a discharge channel.
As part of its planning permission to extend the quarry, Hanson Aggregates proposed using the water to augment river levels and maintain the region's ecological balance, particularly during dry periods.
To ensure the scheme's success, a sump was built in the quarry floor, creating a 7m-deep reservoir.
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The Whately Pumping Scheme relies on a 355kW pump to augment the river and two 250kW levelling pumps.
In addition to augmenting river levels, the reservoir is also used to provide high-pressure water from a 55kW pump that is primarily used for washing stone in the quarry.
To control the pumps, Hanson Aggregates worked closely with ABB's local distributor, South West Industrial Drive Centre (SWIDC), to find a solution.
Because the pumps are on a level in the quarry some 30m below the surrounding land, SWIDC decided to fit four variable-speed drives in a 32ft container, which could be lowered down as a unit.
A 55kW drive is used to control the high-pressure pump and three larger drives are used for the augmentation and levelling pumps.
The container was fully outfitted and tested outside of the quarry and then lowered by crane in a single lift to the pump flat.
The container is cooled separately as it is exposed to direct sunlight and the four drives generate heat inside the container.
SWIDC supplied an ABB ultrasonic level controller to sense the reservoir water level and the augmentation water is tested for turbidity using an ABB controller.
If turbidity exceeds the agreed minimum, a proportional-and-integral (PI) controller operated by the 355kW drive automatically stops the pumps for 30min to allow the water to settle.
Two ABB flow meters monitor the exact flow rates of water.
Similarly, if the water level in the reservoir exceeds 7.2m, the two PI-controlled 250kW levelling pumps are used to maintain the level.
These pumps operate in cascade with one pump starting initially.
In most cases, the first pump has sufficient capacity to handle any excess water.
However, if the water level continues to rise, the 250kW drive reduces the first pump to 80% output before starting the second pump.
It then increases the speed of both pumps in tandem to control the water level.
The water is discharged through a common main into the river.
The ABB drives are programmed to stop all pumping if the reservoir level falls below 6m.
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