DELPORT DU PREEZ AND ASSOCIATES

CONSULTING ENGINEERS AND PROJECT MANAGERS

EBENEZER PUMP STATION

UPGRADING OF EBENEZER PUMP STATION AND PURIFICATION

 PLANT FOR THE SUPPLY OF ADDITIONAL POTABLE WATER

TO RURAL COMMUNITIES IN THE PIETERSBURG AREA

Index: Introduction, Water needs, Description, Civil works, Mechanical works, Electrical and Electronic works, Technical Characteristics, Planning, Contractors, Costs, Acknowledgements.

INTRODUCTION

Ebenezer Dam, situated near Haenertsburg in the Northern Province, is a well known recreational resort both for boating enthusiasts and fishermen. However, few people realise that the one major resource of life - fresh drinking water - is supplied from this dam to a very large portion of the population of the Province.

 The Board of Lepelle Northern Water operates the purification plant and pumping station at the dam and supplies potable water to rural and developing communities in the vicinity of the University of the North and to the town of Pietersburg.

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WATER NEEDS AND INCREASED DEMAND FOR PURIFIED WATER

The original water scheme was completed in 1973 on the grounds of a White Paper WP-D-63 by the Department of Water Affairs. The scheme was known as the Pietersburg Regional Water Supply Scheme and the main objective was to supply Pietersburg, Boyne, Turfloop, Dalmada, Haenertsburg and other small consumers with drinking water.

The original works consisted of a raw water line of 762 mm overall diameter, a flash mixing unit / aerator and four sand filters providing purified water into the 3360 cubic metre fresh water forebay at the pump station. Four pumps with induction motors of 520kW each, employing resistive and auto transformer starting, were used to supply water to the Rustfontein Reservoir (capacity 18 million litres), from where water gravitated to the consumers. The peak delivery was 38 million litres per day.

The guaranteed yield of Ebenezer Dam is 31,7 million cubic metres per year whilst the portion available to the Board for the Purification Works is 18.53 million cubic metres per year.

The original scheme was earmarked for extension in the White Paper WP-I-84 to have an eventual peak delivery of 74 million litres per day. The pump station and purification plant were taken over by the Board in 1992, who then also assumed responsibility for the extension of the scheme to provide the increased demand to new consumers in the adjoining rural areas.

In line with the Reconstruction and Development Programme (RDP), several expanding communities were consulted and a number of water reticulation schemes were planned and some contracts had already commenced at the time of writing this report. On the grounds of the studies undertaken, the Board decided to expand the Ebenezer works so that the projected peak demand figures can be met. With the first phase of implementation the peak delivery of the installation was increased to 51 million litres per day. This will be further boosted to 74 million litres per day with the doubling of the rising main (Phase 2).

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DESCRIPTION OF THE PROJECT WORKS

The original pump house accommodated four pump sets. As no spare space was available in the existing building for the additional pumping equipment, it was decided to add an extension to the eastern side of the building. For aesthetic reasons it was decided to construct the new section using the same design philosophy that applied to the existing facilities.

It was further necessary to increase various components in the water transfer system in order to get the increased flow of water through the purification plant so that the ultimate peak flow of 74 million litres per day through the plant can be realised.

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CIVIL AND STRUCTURAL WORK

 Rustfontein Reservoir in order to allow for the higher operating pressures. As the throughput of water from the purification works had to be increased, it was further found necessary to increase the raw water supply, to construct an additional aerator / flash mixing unit on the northern side of the plant and to enlarge and improve the chemical dosing installation.

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MECHANICAL WORK

The mechanical work consisted of the provision of two dual pump sets, working in tandem (main/booster) configuration, complete with all the necessary valves, actuators, cooling water pumps and ancillary equipment required.

The horizontal split-casing single-stage type HPDM 250-670 pumps were produced locally by Sulzer. The pumps were tested successfully at the factory under SABS supervision before shipping to site.

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ELECTRICAL AND ELECTRONIC WORKS

The electrical work entailed the upgrading of the existing 33 kV/6,6 kV substation with the provision of two 4 MVA power transformers, an incoming 33 kV circuit-breaker and neutral earthing resistors.

In the pump station each pump was fitted with a 6,6 kV squirrel-cage induction motor of 836 kW rating. Due to the weak supply network it was necessary to install a bank of 2500 kVAr line compensating capacitors at the pump station to facilitate direct-on-line starting of the motors. Run-up time for the tandem pump set pair is less than 4 seconds per pump unit with the voltage drop limited to 10% at the point of common coupling.

The switching of capacitor-banks and starting sequence of the pump sets are automatically controlled by means of PLC equipment mounted in the MV capacitor control panels and the motor control consoles. The control system also manages the station power factor so that the station is operated at close to unity power factor.

Each pump-motor set is equipped with a comprehensive set of transducers and instruments linked to the Programmable Logic Controller to provide full operational monitoring and control. The monitoring system is designed to fail to safety. Parameters such as temperature, vibration, pressures and flows are monitored and controlled by the PLC.

Pump set parameters as monitored in the pump station are relayed to the operator's control room by means of a telemetry system over an optical fibre link. The monitoring system was further extended to include monitoring of the existing four pump sets.

The overall electrical consumption is monitored in the main substation by means of electronic equipment, also linked to the supervisory system using a fibre-optic link. The supervisory system provides the operator with warning signals should the demand monitor indicate that the set demand limit is in danger of being compromised. Under voltage protection locks out pump starting during low supply voltage conditions.

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TECHNICAL CHARACTERISTICS OF THE NEW EXTENSION

PROJECT PLANNING AND CO-ORDINATION

Various specialists were employed for certain civil and mechanical parts.

The instruction to proceed with the planning of the Works was issued in June 1992. The Feasibility report was submitted in August 1992. Tenders for the main contract were received in May 1993 and the contract was awarded to Siemens Ltd in June 1993.

The successful tenderer offered a contract period of 67 weeks with the completion date as 23 September 1994.

Practical completion of the works was achieved on 1 September 1994 at which stage the testing and commissioning of the works commenced. Acceptance of the installation took place on 7 October 1994 after successful completion of the test periods.

Official hand over of the installation took place on 25 October 1994.

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CONTRACTORS

PROJECT COSTS

THE CONTRACT WAS COMPLETED WITHIN THE BUDGET AND ON TIME

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ACKNOWLEDGEMENTS

The Project Engineers wish to extend their appreciation and gratitude to the following persons for their dedicated participation to make this a successfully completed project:

The Members of the Board and Staff of Lepelle Northern Water.

The Engineers and support staff of DPA responsible for the planning and design:

The Contractor's Project Engineer and support staff for the dedicated work on site:

P. D. DU PREEZ. Pr. Eng.

PROJECT LEADER

DELPORT DU PREEZ AND ASSOCIATES.

24 OCTOBER 1994.

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