Redeveloped aquatic centre utilises EtherNet/IP
The Ruth Everuss Aquatic Centre at Lidcombe in Sydney’s west has been closed since June 2015 for extensive redevelopment. However, the reopening in April 2017 unveiled a site that had been transformed into a state‑of‑the‑art facility.
While the transformation has undoubtedly been significant, great care has been taken to preserve the heritage status of the facility, which was built in 1959. Some of the existing buildings were demolished, but many have remained or been refurbished: examples include the grandstand, stanchion and shelters around the main 50 m pool, which will include a ninth lane and ramp for wheelchair access. While many new facilities were built, it was mandated that the look of any new construction fit in with the existing facilities.
Apart from the main outdoor facility, the revamped centre also includes two water polo pools (indoor and outdoor), a six-lane 25 m indoor pool and a program pool for rehabilitation. For families, there’s an outdoor splash pad and an indoor leisure pool, complete with numerous jets, air blowers and spas. Other new features include lighting for night-time use and heating for year-round patronage.
Keeping all these facilities running is a surprisingly complex control system. It monitors a range of parameters for each pool, including water levels, chemical dosing, water temperature and filtration. For this, the plant rooms have an intricate web of reticulation pipes, with accompanying pumps, sensors and filters.
An advanced filtration system is used to remove solids from the water. Each pool has two filtration pumps to sift and remove both coarse and fine particles. The active filtering agent is DE (diatomaceous earth). For DE regeneration and backwashing, the controller is required to run a separate vibratory routine for 30 seconds on each of the filters. This operation shakes the DE from the socks in the filter and extends its life.
Pool water is kept clean by an automated chlorination system, also controlled by the central controller. Two types of chlorination are used — inline salt water chlorination for the saltwater pools and granulated chlorine for the freshwater pools. Chlorines are an effective disinfectant but can be expensive. So to prolong their life, the pH level of the pool water is maintained at 7.2 by dosing with CO2. This required special controlling circuits to be constructed within the PLC program.
For further purification, the indoor pools have UV steriliser treatment to remove remaining chloramines and other impurities.
The water temperature is maintained by the use of heat pumps. Heat pumps exchange heat with the complex’s air-conditioning system, recycling heat that would otherwise be dissipated into the atmosphere. They are used in preference to gas heating, as they are more economical to run.
The temperature needs to be strictly controlled within a 0.4°C band, requiring a series of high-precision RTD sensors to be employed. One potential problem found in many heating applications is temperature inconsistency, where the whole load is not at one uniform temperature. This is overcome by constantly cycling water through the pools.
In order for the many water features to work properly, constant water pressure needs to be maintained.
“Controlling water flows to maintain constant pressure proved surprisingly difficult. PID is normally adequate for this type of control, but in this case, the pressures fluctuated too erratically and PID loops could not respond quickly enough,” said Bob Bishop of Engineered Control Systems. A dedicated function block needed to be designed for this and it ensures constant water pressure.
Omron’s CJ2M series PLC was selected as the controller. It supports a sophisticated set of instructions needed for the control systems, including user-defined function blocks. It can also handle in excess of 2500 I/O and has an EtherNet/IP port on board for networking. A remote network was needed as both machinery and control panels were distributed across the five main areas within the complex.
The digital and analog remote I/O is connected to Omron’s NX remote I/O blocks, which are linked to the CPU via EtherNet/IP. All wiring is ferruled, meaning it can be quickly pushed into screwless terminals without tools. The terminals apply consistent pressure to the wire for a secure, lifelong connection, which is also more resilient to vibration that standard screw terminals.
For operator control, some parts of the complex plant use conventional indicator boards and push-buttons. Other areas use HMIs, which are linked over the same Ethernet connection as the I/O.
Originally published here.
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