Department of water affairs and forestry technical guidelines for the development of water and sanitation infrastructure

12.7Control systems

12.7.1Control modes

Local and remote control modes are required, i.e.. it must be possible to switch between local and remote control.

Both control modes can be either automatic or manual.

Distributed control should be employed with override and monitoring by the telemetry system.

Failure of the telemetry system should not affect the local control.

Telemetry must not be able to start or stop in local control.

12.7.2Man machine interface

Computers must be specified as follows:

• 
  17 inch monitor;
  
• 
  Pentium IV 2GHZ or higher
  
• 
  40G Hard Drive
  
• 
  At least 512 MB memory.
  

A display unit must be provided or the existing display upgraded or reprogrammed at the master control panel to display all the data and control parameters from the out stations, including all alarms, equipment status, valve positions, levels, etc.

All controls should be effected from this interface, either automatically or by the operator when selected.

Sufficient data storage capability must be provided for backup and data storage.

12.8Power supplies

Suitable power supplies with adequate battery back up facilities must be provided.

The batteries may be charged from one of the following sources:

• 
  AC main supply with rectifier and protective equipment
  
• 
  Solar cells
  
• 
  WIVA chargers.
  

Solar cells will be used where no mains power is available.

Alarm signals should include the following:

• 
  Low battery voltage;
  
• 
  Mains failure (if applicable);
  
• 
  Solar panel (if applicable);
  
• 
  Intruder alarm;
  
• 
  Communication failure.
  

In general the power supplies must conform to the following:

• 
  Output voltage: 12 Volt for normal use or 24 Volt for transducers;
  
• 
  Protection: Overcharging, under voltage, cut out, power surges, reverse polarity.
  

Rating:

• 
  Data transmission only: 30%Transmit/Receiver 70% standby for 48 hours;
  
• 
  Data and Voice transmission: 50% Transmit/Receiver 50% standby for 48 hours.
  

12.9Lightning protection and earthing

Suitable protection must be provided to protect equipment, including:

a) Earth Electrode System

• 
  Maximum resistance 5 ohms. 1 ohm if possible;
  
• 
  Test points are to be provided;
  
• 
  SANS 10199 is applicable;
  
• 
  Concealed joints and interconnections brazed or welded.
  

b) Bonding all exposed steelwork and other steelwork that may become "live" due to equipment faults, static build up or lightning strikes are to be bonded.

c) Lightning Protection
All equipment should be considered exposed to lightning strikes and suitable protection must be provided.
All instrument boxes should be earthed by a 70 mm copper earth wire.

12.10Documentation and training

Complete maintenance and operating manuals must form part of the scope of supply.

As-built documentation must be provided and must include:

• 
  Control logic;
  
• 
  Cabling; and
  
• 
  Physical layout.
  

Operating and Maintenance manual must also be provided.

12.11Spares

A full set of spares must be included with the manuals.

13PIPELINES

13.1General

Water supply is delivered under pressure either by gravity or by pumping.

Water supply pipelines are generally designed to convey water free of suspended matter and generally of potable quality.
Laying and jointing are important operations that contribute to the life of a pipeline and to the level of service provided. These can constitute a significant factor in pipe selection, especially where labour based construction methods are utilized.
The prime function of any pipe and pipe material is that, for the expected life of the pipeline, there is adequate resistance and strength to withstand all forces that can be expected to be imposed on the pipe. These forces and requirements include:

• 
  Internal forces including internal pressure and pressure surges;
  
• 
  External forces including earth pressure and superimposed loads;
  
• 
  Water tightness; and
  
• 
  Corrosion.
  

Generally refer to DWS 1110 Clause 4 (included in the Specifications Folder) for the design and setting out of pipelines.

13.2Design capacity

See Planning and Design Parameters in the Preliminary Design Section.

13.3Pipeline materials

The pipeline material that provides the lowest life cycle cost should be selected. The selection procedure as proposed in Section 3 of Darling and Hodgson’s “Pipe Selection Manual, 1996” is recommended.

Suitable pipeline materials are tabulated below:

Pipe Materials, Classes and Acceptable Sizes:	DWAF DWS Specification	Class (bar)	Sizes (mm)
Minimum pipe size for reticulation: 50mm nominal diameter
HDPE (SANS 533)	None	Min. Class 6	15 - 75
uPVC (SANS 966 or ISO 4422)	DWS 1160	Min. Class 6	50 - 250
Note: 125 and 140 mm sizes are not recommended for uPVC pipes, due to the lack of standard fittings.
21GRP	DWS 1150	Min. Class 6, Max. 25 bar	Min. 150
Galvanised Mild Steel (SANS 62)	None	Medium Duty	15 – 150
Steel (> 150mm)	DWS 1130	Min. API 5L Grade A Min. wall thick. t = 4,5 mm Slenderness, D/t < 120	Min. 200
	Max. Press. incl. surge (m) = 120*t/D, where S = Yield Point Stress (MPa) and D = Outside Dia (mm). Formula assumes max. of 60% of yield stress mobilised.
Protection to steel pipes (> 150 mm):	Generally bitumen fibre wrap coating with cement mortar lining or epoxy lining and cathodic protection – see DWS 1131.