DELPORT DU PREEZ AND ASSOCIATES

CONSULTING ENGINEERS AND PROJECT MANAGERS

BULK WATER METERING FOR VOSLOORUS

Index: Introduction, Design Consultants, Communication and liaison, Anticipated design problems, Flow analysis,Flow meters, Equipment housing, Implemented System, Civil works, Telemetry system, Central, Problems Encountered, Financing, Acknowledgements

It was therefor decided to implement a bulk metering system so that the flow of water through the main network of pipes could be monitored and analysed.  This would then enable the council to optimise the design and improve the service to it’s customers.

Changes to the Water Act also imposed a responsibility on the Council to implement measures to improve service delivery and reduce losses.

Design Consultants

An application was lodged with the EGSC for assistance and funding of the Bulk Water Metering Project for Vosloorus.

This was approved by the EGSC and the following team of Consultants were appointed:

• Delport Du Preez and Associates for overall management of the project and design of the Electronic systems
• Booyens and Koorn for the civil works portion of the project.
• Thari Entso Consultants for Social and community liaison.

All these consultants had extensive experience with the implementation of community water projects

Communication and Liaison

Mr. Clive Bapela of the firm Thari Entso assumed responsibility for community liaison.  With his team of helpers they arrange a number of introductory meetings with the communities, explaining the project and it’s benefits.

This was followed up with the issue of notices to occupants of affected zones during the course of construction of the works.

This process resulted in a relatively peaceful contract with no serious incidents of unrest or labour disputes.

Anticipated Design Problems

During initial discussions a number of items were identified as problems requiring specific attention:

• Flow Patterns
• Flow meter types
• Housing and support structures
• Power supplies

Flow Analysis

The water network for Vosloorus was divided into a low pressure zone gravity fed from the reservior and a high pressure zone serviced by a water tower. 

The flow rates and delivery pressures in the various zones were not known and a specialist consultant was appointed to undertake a theoretical analysis to determine flow rate and pressure parameters for the design.

This analysis also indicated desired points for the placing of flow meter stations

The study resulted in the selection of 22 bulk meter positions.

Flow Meters

Boksburg water department operated an existing network of bulk meters in Boksburg and had very good experience with the use of Meinecke’s propeller type flow meters (Type WPD).  It was therefor the logical choice.

As far as the electronic sensing of flow was concerned:  two methods were available - optical conversion and pulse counting.

Optical conversion - the speed of the gears is converted to a frequency, which in term is converted to a current. The double conversion process has inherent stability problems.

The pulse method provides an accurate accumulated flow reading, but flow rate is derived. The sensor is simple, cost effective and very reliable

For reliability reasons it was decided to use the pulse method

The Implemented System

Two main contracts were awarded for the construction of this bulk water metering system:

•Construction of civil works and the installation of flow meters - Du Toit Blasting and Digging

•Supply, installation and commissioning of the telemetry system - Prodesign (Pty) Ltd

The Telemetry System

Implementation of the telemetry system went well and no technical problems were encountered.

The project programme was seriously affected by two aspects that were completely beyond control:

• Provision of electrical power by ESKOM.
• Approval of a Radio Communication Licence by SATRA (now ICASA)

As part of the contract two sewerage pump stations had to be upgraded:

• The electrical switch panels were replaced and at the same time equipped with monitoring interfaces.
• The high level alarm switches were telemetered back to the control centre.

The Telemetry Central

The master station was configured to operate with the US DATA Factory link software package.  This is a standard application with very powerful reporting systems.

Distributed operation of the master station was implemented as part of the contract.

Four remote terminals operating over the Council’s WAN was provided at the service depots and at the control room of the Emergency services.

Essential alarms are reported to the control room, from where the standby officer is contacted.

Problems Encountered

The selection of the type of flow meter to be used eventually appeared to be unfortunate:

The first problem encountered was that of vandalism.  Some meters had been damaged before installation had even been completed.  This problem was eventually overcome through the use of substantial covers.

The second problem was internal damage to the meters.  Two causes were identified. 

In the first place the flow rates in some instances far exceeded the predicted values, causing premature failure.

In the second place it was found that the pipe network contained a lot of debris (stones, steel rods, etc).  These items cause a lot of damage to the mechanisms.  The problem is fixed by the insertion of strainers.  This however causes a maintenance problem, as these strainers need cleaning.

With hindsight it might have been better to have selected a non-intrusion type of flow meter:

• At the water supply scheme for Walvis Bay we were involved with the replacement of Meinecke meters with Orifice plate and ultrasonic flow meters.  In this instance the presence of fine sand in the water caused premature failure of moving parts.
• The Department of Water Affairs and Forestry as a standard practice make use of Sparling Ultrasonic bulk flow meters, with great success. 
• The Lepelle Water Board in the Northern Province make use of E&H electromagnetic flow meters for bulk flow metering purposes.

Although the initial cost of procurement appeared to be substantially higher, the cost is soon offset through the lower cost of maintenance and operation.

Some further problems of an irritating nature needs to be pointed out:

• The interruption of the mains supply to the telemetry stations continue to be a problem.  The control over power connections seem to have lapsed and the telemetry outlets are regularly replaced by illegal feeds to consumers.
• Urinating against the outstation housing is a further problem.  The fluid penetrates the structure through the door gaps and causes internal damage.  In some instances the council was forced to erect fences to keep people away.

FINANCING

Financing for this project was provided by the Eastern Gauteng Services Council.

The initial amount requested was   R 4 334 487.00

The amount approved was            R 3 500 000,00

The final amount was                     R 3 321 007,53.

The final amount was made up of:

–Civil works                        R  1 725 328,54

–Pipeline analysis               R       38 400,00

–Social consultant               R       40 500,00 

–Fees and supervision      R     257 371,89

–Electronic works               R  1 053 245,51

–Fees and disbursements  R     170 399,19

–EGSC levy                      R       33 502,26

Acknowledgements

 My appreciation and thanks to the following persons and organisation that made this project possible:

•EGSC: Mr. D van der Merwe and P de Vries

•Boksburg TLC: Mr. C Kroon, K Botha, A van Wyk

•Booyens & Koorn: Mr. P Swiegers

•Prodesign: Mr P Cherry, P Raines

• Thari Entso: Mr. C. Bapela.

© - 1998, 1999, 2000, 2001  DPA CC.

Prepared by P. Du Preez. Pr. Eng