Page 11 - EngineerIt April 2021

MEASUREMENT AND INSTRUMENTATION

Keeping our bridges standing

Taking on the challenge of unmonitored concrete assets

By Gary Bradshaw, director of Omniflex

Most bridges are constructed using steel rebar reinforced concrete, and many of these structures
use cathodic protection (CP) systems to keep the vital steel reinforcement from corroding.
This article discusses the problems inherent to CP system monitoring, and describes
the modern approaches that make it feasible.

xpected to be completed in 2024, An endless task
the Msikaba bridge, spanning the So, how are you supposed to know if a CP system is even working if it is not being
EMsikaba River in the Eastern Cape monitored?
of South Africa, will stand at a height of When left unmonitored, there is no way to be sure that the system is functioning.
approximately 580m. Using 2,700 tonnes of It could have been damaged or could even have been installed incorrectly in the first
steel in its construction, it will be the largest instance — the install-and-ignore approach leaves endless scope for malfunction while
bridge on the continent and promises to be exhibiting no external warning signs until it is too late.
a real feat of engineering. When compared to impressed current CP systems, remotely monitoring galvanic
A big part of keeping road infrastructure CP systems are a far more difficult proposition, because they work with passive
standing and safe over many decades is by electro-chemical currents. This makes them ideal when power and telecom access
using CP, both impressed current (ICCP) is not available, but it can be very costly and time consuming for the engineers who
and galvanic CP. These systems induce need to travel to the structure and physically measure the galvanic CP current with a
a positive charge in the reinforcing steel multi-meter.
rebar, which repels the positively charged Furthermore, there may be hundreds of discrete galvanic CP circuits on a bridge,
chemical radicals that would normally which quickly adds up across the many bridges in South Africa.
corrode the steel. In ICCP systems, this
charge is induced by an external power Using the data highways
supply, while galvanic systems use a So, how do you monitor tens of thousands of critical assets, spread over thousands of
sacrificial anode, formed from a material miles and often found in remote places? One way is to send the monitored data over
with a greater electro-chemical potential the internet.
than the steel rebar, such as zinc. Manufactured in South Africa, Omniflex’s iGAL galvanic CP monitor is unique in this
arena. It is battery powered so can be installed quickly and easily. It really is as simple
Unmonitored variables as connecting the anodes, reference electrode half-cells and switching it on.
The monitoring of CP systems is not The wireless and SMS capabilities further remove the requirement for any local
mandatory in South Africa, unlike in the networks. Instead, the iGAL transmits its data entirely wirelessly to the web-based
UK where legislation states that all CP PowerView CP portal, which can be accessed through a web browser via a secure
systems should be designed with full in-built password from anywhere across the globe.
monitoring. By using galvanic CP remote monitoring systems, the imposing, intensive and time-
The Southern African Universities consuming job of physically monitoring galvanic CP assets becomes so much easier.
Power Engineering Conference tried to Instead of jumping in the van and closing part of the highways to physically measure CP
change this in 2019, by publishing an article equipment thousands of times over, engineers can monitor CP assets from anywhere in
aimed at establishing a CP system design the world through the PowerView CP portal. Any problems are immediately reported by
framework, inclusive of analytical monitoring SMS and emails and tests can be remotely performed.
via a computer software package. This acts It’s remarkable, the work that goes into keeping seemingly stationary pieces of
as a guideline to petro-chemical industries infrastructure safe and standing. To find out how Omniflex remote monitoring CP
but is also implied for larger steel structures. solutions can help keep your assets structurally sound, visit www.omniflex.com. n

EngineerIT | April 2021 | 9