Civil Engineering Reference
In-Depth Information
circuit diagrams for maintenance and easy access to fuses and other
consumable and replaceable components.
There are two opposing directions of T/R design at the moment. The first
is to make a simple, rugged reliable design with high-quality components.
This is checked manually every one to six months and an annual 'service'
carried out. The other is to attach a microprocessor and logger system that
can monitor and control the system. This means that data can be collected
remotely and in some designs the system can be adjusted without regular site
visits, requiring only an annual inspection as long as local personnel carry
out quick checks on the condition of the systems (loose wires, etc.).
The number of systems an organisation has in operation is one factor
in choosing remote control. It becomes more cost effective to collect and
review data without site visits as the number of cathodically protected
structures increases. The sophistication of the client and his consultant is
another factor.
The reliability of the microprocessor system has not been reported in
the technical press; the author's first few remote control systems installed
in 1986/7 worked until the structures were demolished, although most
of those were installed inside buildings, in very benign environments.
Some systems are comparatively simple and will only monitor on and off
potentials, current and voltage. It is not possible to change the current
or voltage settings remotely on some of these systems. With modern
microprocessors and the internet it is possible to store data online, and
send alarms by email or text message if the system malfunctions or exceeds
defined limit values of current, voltage or reference electrode potential.
Systems have been developed that will commission and operate a system
according to BS EN12696, the British and European standard for cathodic
protection of steel in concrete.
Design, installation, monitoring and maintenance
An impressed current cathodic protection system can be procured by a
number of routes:
• Design, build and commission by an experienced contractor, usually with
an independent design check with all responsibility on the contractor.
The client must provide as much information as possible about the
structure and the contractor may have to carry out investigations as part
of the works.
• Detailed performance specification and outline design by the client's
engineer with the contractor carrying out a detailed design. The client's
engineer should have carried out most of the necessary investigations
and testing prior to issuing the tender documents.
• Detailed design by the client's engineer with the contractor selecting
products to meet the design requirements and installing the system,
