“Healthy“ Pumps Due to I/O Remote-I/O-System Facilitates Condition Monitoring of Pumps for Desalination of Sea Water
At the beginning of the year, a large desalination plant was put into operation on Australia‘s Gold Coast. It delivers 125 million liters of drinking water each day, which in this dry region corresponds to 20% of drinking water requirements. For this project, Nijhuis Pompen BV of Winterswijk – part of the Norit Group – delivered and installed 42 pumps.
At the customer‘s request, some pumps use condition monitoring, where the vibrations are measured using sensors and measurement modules on the Wago-I/O-System. Precisely on the day on which André Betting visited the seawater desalination plant, the Gold Coast Desalination Plant in Tugun, Southeastern Queensland in Australia, it was raining cats and dogs. André Betting is a project manager at Norit Nijhuis who was on-site for some final work on the pump systems. It is almost a little depressing after people have worked for nearly two years on this 1.2 billion dollar project when shortly before start-up, fresh water (rain) simply falls from the sky. The necessity of such a plant is nevertheless controversial: it should bring to an end the threatened shortage of drinking water in a region whose economy is growing steadily. For years, this region has struggled with ever-drier conditions, and the population is growing by 55,000 people per year, which puts constant pressure on the water supply.
Drinking water from the sea
To make drinking water from sea water, a 2.2 km tunnel with a diameter of 3.7 m had to be drilled in the bedrock in Tugun in order to draw sea water from the coast approximately 1.4 km away. At the height of the desalination plant, a 70 m deep shaft was dug that opens into this tunnel. The other side of the tunnel ends in the sea approximately 40 m under the subsiding sea floor. Here too a shaft was dug, from which sea water is drawn at low speed via an intake approximately 20 m under sea level in order to protect the sea flora and fauna. The law of „communicating pipes“ ensures that the sea water climbs passively until approximately 20 m below the ground level of the system. The remaining level difference is pumped up with four vertical turbine pumps. Each of these pumps has a capacity of 5,000 m3 per hour – with a hydrostatic head of 23 m.
In a pre-treatment phase, organic material is removed from the water. Subsequently, the water is subjected to additional treatments in order to correct the acidity and chlorination, and it is then pressed at high pressure through several membrane filters (reverse osmosis). The reverse osmosis procedure performs the actual desalination: the water molecules pass through the membrane, while the salts and other particles are left behind. This process is very effective and filters out 95 to 99% of the salt. In a post-treatment step, the water is brought up to drinking water quality and stored in huge containers. From there, it travels through two newly-built pump systems and a 24 km pipeline into the drinking water network. The volute casing pumps used for this have a capacity of up to 2,400 m³ per hour, with a hydraulic head of up to 135 m. Various pump models from Norit Nijhuis are used in the whole project.
Machine health is determined
Condition monitoring is being used ever more often in order to be able to detect damage to pumps early. Here, the state of the pump is monitored, among other things, using vibration measurement and analysis. The client also requested this method for some pumps. The information about the „health“ of the pumps should be made available to a SCADA system via a Profibus network. Since in the desalination plant a majority of the automation was already equipped with Wago components, Norit Injhuis sought contact with Wago Holland. For the condition monitoring, information such as the temperature of the bearings and coils and the vibrations of the pump had to be forwarded to the SCADA system. The multi-faceted Wago-I/O-System 750/753 with Profibus coupler was used for this. On the intake side of this modular automation system, special sensors for vibration and temperature signals are connected via I/O modules. The entire system could be assembled completely on the respective pump. The installation and start-up of the system took place at Norit Nijhuis in Winterswijk. Karel Gering, Manager of Project Engineering at Norit Nijhuis: „We only participated in a morning-long training session at Wago; after that everything was clear and we were able to set the entire apparatus correctly.“
Flexibility pays off
The installation went smoothly in Australia. But as often happens with a project, the client made changes on-site. First, it should be possible to process all information centrally via the SCADA system. Later the request was to implement local information processing for the larger pumps. The pumps must function independently and be able to react directly to signals, even with possible disturbances in the network. Furthermore, it must be possible to operate the functions using a local display. These changes required a programmable controller, which in turn required the corresponding software. Norit Nijhuis itself did not have the expertise to do such specific programming. The completion date for the project was coming ever closer, therefore, haste was required. Wago Holland suggested three software companies; IACT of Haaksbergen received the order. Within a few weeks, it programmed an application for the controller based on CoDeSys 61131-3. Karel Gering confirms: „This time too the installation and start-up went smoothly and we were able to adhere to the deadline. A next order for a large project in Australia has already been placed!“