Fluvial Design Guide - Chapter 11

River and canal structures

11.7 Instrumentation, control and automation (ICA)

11.7.1 Forms of control

Ideally, gates and pumps should have only local manual operation for the following reasons.

  • This is safer for staff and the public in the area.
  • It is technically simple and economical.
  • It ensures that an operator is by the equipment for and during its operation. This allows items to be checked and ensures that signs of distress in the equipment can be observed and appropriate action taken.

In practice, remote and automated operation is frequently required. Remote operation can be:

  • within a short distance of the equipment, but where the operator is more comfortably housed and can probably see the equipment to some degree – in such cases remote operation may well be achieved by hard wiring;
  • truly remote from the site, where there is no visual contact (unless by CCTV) and where control links are achieved by telemetry or similar.

Considerable attention must be paid to safety when remote operation is adopted and local control facilities must be retained for maintenance purposes. Specific requirements are laid down when remote and automated operation is used for Environment Agency projects (Environment Agency, 2006).

Typical examples of where automatic operation is appropriate include:

  • drainage pumps;
  • gates that control the water level in a river or canal.

For gates, mechanical means of achieving automatic operation are possible – either as one-off designs such as the Pulteney weir in Bath or by traditional proprietary designs. These have the advantage of limited or zero energy consumption, and lack of dependence on a power supply.

For gates and pumps, automatic operation can be achieved readily in forms that range between:

  • those based on simple level switches and limit switches;
  • systems using PLCs to allow operation in accordance with sophisticated and readily changeable operating criteria.

11.7.2 Alternatives for remote linking

In most situations it can be uneconomic and/or environmentally unacceptable to provide traditional hardwired instrumentation and control systems over a distance of more than, say, one kilometre. Clearly exceptions to this can occur, for example on a large site where multi-function service corridors are provided.

For remote operation where such hardwiring is inappropriate, the principal options for the communication of instrumentation information and operating commands are described below. Combinations of these are also common.

Extended local area network (LAN)

Control and monitoring equipment is frequently connected using a LAN. Network distances can be extended by the installation of fibre optics, which can extend the traditional distance of an Ethernet network, for example, from 100m to several kilometres. They can be installed in ring configurations for redundancy.

Fibre optic networks are suitable for large sites where access is available to lay cables in service corridors and ducting without interruption.

Radio system

The use of radio systems is declining, as other systems achieve higher reliability and flexibility. Where the use of telephone systems or similar is difficult, such a system could be considered for linking over a distance of a few kilometres.

In principle, radio systems are suitable for a central site communicating to one or more outstations. The limitations are down to radio reception and usually require line of sight between the transmitter and the receiver for communications to work.

Public switched telephone network (PSTN) system

This analogue alternative is also declining in use, superseded by more comprehensive and advanced systems (see below). This system uses modems to allow transmission and receipt of digital signals through either dedicated lines rented from BT and others or on-demand dial-up arrangements.

PSTN or leased line communications are suitable for small amounts of data that are not required to be updated very frequently. Such systems can be expensive and slow.

Broadband-based system

These use the traditional wired telephone system at both the site of the equipment being controlled or monitored and the remote location, connected via a modem or a router. This arrangement can provide access from anywhere with an internet connection, provided that the correct security privileges are used. A virtual private network (VPN) can be configured in addition, providing a dedicated connection between systems if required.

Broadband-based systems are suitable for connecting several different locations that can be large distances apart, nationwide or even worldwide.

Successful use of this technology relies on a good broadband connection.

3G cellular telephone system

This uses the 3G (third generation) cellular telephone network to achieve broadband data communication between sites without the need to use the traditional wired telephone system. This system is not suitable for permanent connections as connection time can be expensive. It is suitable for remote outstations, provided they have good 3G cellular telephone coverage.

 

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