• • • TEST & MEASUREMENT • • •
How one of Australia’s key ports tackled corrosion
When New South Wales Ports embarked on a two-year programme to rehabilitate the structures and combat corrosion levels at its Bulk Liquid Berth 1 (BLB1), it commissioned Melbourne-based consultancy Infracorr to deliver a bespoke cathodic protection (CP) system
D
esigning the system presented several challenges because BLB1 houses hazardous gas, petroleum and chemical
pipelines that could be at risk of ignition if exposed to unsafe levels of voltages and currents. To safely deliver the system, the consulting firm
engaged cathodic protection specialist Omniflex to support the hazardous area and remote monitoring aspects of the CP system design. Over the last decade, reports have established
that chlorine-induced corrosion is affecting some of the major structures at NSW Ports, including Sydney Harbour and Port Botany, Australia’s largest container port. NSW Ports commissioned Infracorr to design a
CP system for use at BLB1, which is located at Port Botany and houses hazardous gas pipelines. The project also included the repair of defective concrete structures, which were suffering from the effects of corrosion and concrete spalling in the many pre-stressed beams and headstocks of the various bridges and catwalks at the port. The project consultant said: “The system needed
to be designed to allow for tight control of the currents and voltages used across the site for two key reasons. “First, Port Botany is NSW’s main bulk liquid
and gas port and BLB1 is a key part of this facility, playing an active role in loading and unloading volatile liquids and gases. These hazardous materials are present in the environment on an ongoing basis, meaning that any stray sparks caused by excess voltages and currents could become an ignition source for a major fire or explosion. “Secondly, because many of the structures present are constructed using pre-stressed
concrete, it was extremely important that all electrical currents applied were carefully controlled to avoid structural damage caused by over protection.” The consultant continued: “To control corrosion
in steel it is necessary to give it a more negative electric potential than its environment by 800 mV. However, if the charge applied results in the steel being more than 1 V negative than its environment, hydrogen embrittlement can occur, leading to failure of the steel and long-term structural damage that is not easily repaired.” Ashley Rangott, asset manager at NSW Ports,
said: “One of the big technical challenges for the project was that there is no off-the-shelf CP system available that has certification for use in zone 1 classified hazardous areas. “This meant that we had to go through the
process of designing a bespoke system that met the cathodic protection objectives, including dealing with the challenge of prestressed concrete, and a system that could be certified to meet the necessary requirements under AS60079 regulations.” The system designed for use at BLB1 by
Ian Godson, director at Infracorr, was a hybrid CP system that combines the properties of both passive galvanic and impressed current cathodic protection (ICCP). It works by inserting specially designed anodes directly into the structure in a matrix. A voltage is applied to force salt migration from the steel to the anode and passivate the zone. When the zone is sufficiently charged, the power source is disconnected and the sacrificial anodes are left to operate galvanically, providing passive protection to the structure.
“The decision to go with a hybrid CP system was
jointly made between NSW Ports and the project consultants. The hybrid system reduces the ongoing risk of hydrogen embrittlement on prestressed concrete elements that a standard ICCP system presents,” added Mr Rangott. The system uses remote monitoring technology
to provide asset managers with ongoing reassurance that systems are operating as intended and corrosion levels are under control. To deliver this, Godson requested the assistance of Omniflex to advise on the hazardous area and remote monitoring aspects of the design. David Celine, managing director of Omniflex,
said: “Because of the low currents required to meet the prestressed steel and hazardous area limitations, the hybrid CP system required an initial power-up phase of three to four months before the external power source was disconnected and the system left to operate galvanically. “The system comprises of nearly 35,000
embedded hybrid anodes that were installed in the structures at BLB1 and is designed to control corrosion for up to 50 years. Because of BLB1’s ongoing operational nature, extra controls were put in place to manage activities across the site during the system installation phase. Mr Celine continued: “Because this was the first
large scale implementation of hybrid CP used in a working hazardous area anywhere in the world, some components needed certification for the design to meet the requirements of AS60079 as an intrinsically safe certified system. “Most countries have their own certification
process so it can be costly and time consuming to get installations like this one certified as being intrinsically safe.
42 ELECTRICAL ENGINEERING • JULY/AUGUST 2022
electricalengineeringmagazine.co.uk
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52
