A significant part of control system design for moving structures begins with a safety case which assesses how the structure impacts on the safety of the user, the public, maintenance personnel and its own potential loss of asset, for example how a failure of the control system can lead to damage to the structure itself. This study forms one of the cornerstones of the control system design by determining the required safety functions.
Working to the guidelines set out in ISO 13849 and IEC 61508 Functional Safety of Electrical and Programmable Control Systems, our TUV accredited functional safety engineers have extensive knowledge and experience in conducting Safety Integrity Level Assessments to determine how the control system can best deliver a safe operating environment to all stakeholders.
The Built Environment – On the move
The built environment comprises of places and spaces created by people in which, on a day-to-day basis, they can live, work and more importantly play! We have played a part in some fascinating, and often iconic, moving structures over the years – designed to improve the leisure experience of those who use them.
Fairfields specified, designed, built and commissioned the core control system which is responsible for controlling the movement of the roof. The final commissioning of the four year-long project was concluded in 2009, and our engineers have been providing ongoing maintenance for the system ever since.
The roof consists of 10 trusses running on two parallel tracks. Each truss is 77m long, weighs 100 tonnes and is equipped with two Schneider PLCs, each controlling up to 4 lock motors and 8 Moog servo drives. A master Schneider supervisory PLC controls the opening and closing sequences, ensuring that the 8 minute operation is controlled to a 0.1mm resolution and achieving a total end to end tolerance of only 30mm. This process requires 4000 I/O points which are monitored and logged every second through a bespoke SQL database and RSview 32 SCADA system, both of which were designed, configured and extensively tested by our own in-house design team.
Fairfields has had the honour of designing the control and monitoring systems for 2 of the UK’s most iconic structures; the Anderton Boat Lift and the Falkirk Wheel.
First built in 1875, this was the world’s first boat lift and was originally built to speed up the movement of cargoes between the River Weaver and the Trent and Mersey Canal. The plan was to restore the lift back to its 1875 hydraulic operation and Fairfields won the contract to design and install the new electrical system. This was made all the more challenging as the new hydraulic system had to be integrated into the original structure along with integrating the legacy of the gates and wedges into the modern day control system.
Fairfields designed and implemented a control system with a Rockwell Automation SLC PLC at its core, which interfaces with 6 flex I/O nodes, 11 E3 intelligent starters 4 Panelview HMIs and 2 RSView SCADA systems.
This is the world’s first rotating boat lift, measuring an impressive 35 metres in height. It was designed to ‘bridge the gap’ between the Forth & Clyde and the Union Canals, restoring the waterway between the cities of Glasgow and Edinburgh. Fairfields was awarded the contract to design and install the electrical system. This controlled the hydraulic drive system which is responsible for wheel control and whole site water management. This is pivotal for the continued operation of the wheel. From this PLC and SCADA based system, all other major functions can be viewed and controlled, including; the lighting system, CCTV, fire and intruder alarms, and the tunnel.
The boat lift consists of two support arms, each weighing approximately 500 tonnes and measuring 38 metres in diameter. These are linked by one centrally located load bearing axle and measure 26 metres in length by 3.8 metres in diameter and is of hollow construction. These support arms support the 2 gondolas. Each gondola houses a Schneider M340 PLC performing local control functions, data gathering and relay. The PLC network is made up of a number of Schneider momentum nodes which relay I/O back to the master Premium PLC. The PLC is housed within the main hydraulic MCC located in the central wheel building. Operators are able to control and monitor the Union Canal locks, the tunnel, aqueduct, the boat lift, basin and associated locks into the Forth & Clyde Canal from one of three SCADA systems. The system as a whole has an I/O count of over 600 points.
Automated Crane Handling Systems
An overhead travelling crane may not immediately spring to mind when considering moving structures, however, we have provided a number of bespoke handling solutions for automated cranes and handling gear in recent years:
- Nuclear power station de-commissioning cranes
- Nuclear power station de-commissioning retrieval masts
- Nuclear submarine fuel cell handling cranes
- Advanced aerospace engine handling and support systems
- Personnel emergency escape
A further development of the crane handling systems is the Automated Storage and Retrieval Systems, an example of which is the Aluminium Rolling Mill in Oman. Here, the systems are issued unique product storage locations, customer and tracking information by a top end SAP management system. The handling systems automatically instructs the crane(s) to transport the product to the required destination and unload in the desired location. The locations and all associated data are stored in a bespoke database which not only permits the product to be retrieved automatically at a moment’s notice, but also provides a fully auditable documentation trail. These systems are implemented using a ground based PLC which communicates with the cranes on-board PLC via a distributed industrial wireless network, permitting real time interaction and monitoring.
In an age where the need to get around is fundamental to both business and leisure activities, the reliability of transportation links is paramount. We have been involved in a number of transportation related projects over the years, from bridges to Ro-Ro (roll-on/roll-off) ferry loading systems.
The Isle of Wight Red Funnel
For the Red Funnel, hydraulic link spans are used to load and unload vehicles from their ferries at the Southampton and Cowes terminals. The control system employs two hydraulic power packs and one standby diesel generator to achieve maximum availability and minimum downtime. The operations of the link span are controlled by a Groupe Schneider Premium PLC. Four pressure transducers monitor the hydraulic cylinder pressures. Whilst inclinometers monitor the lateral movement of the linkspan, the PLC actively adjusts the position of the cylinders in order to maintain the level of the link span.
The Woolwich Free Ferry
The Woolwich Ferry provides a free Thames River crossing service. It comprises of a north and south bank terminal, operating with up to two Ro-Ro ferries with a third in maintenance/reserve. When a ferry is positioned at one of the terminals, two independent linkspans can be lowered down to meet the ferry. Once the linkspans are in contact with the ferry, the system enters a float mode, allowing the ferry to rise and fall with the tide, wash and load transfer whilst maintaining contact with the ferry.
The control system is based around a Siemens S7 TIA platform, incorporating:
- 4 off S7-1500 CPU1516F (Safety PLC)
- 800 I/O points
- 4 off CU320-2 Sinamic Drive systems
- 6 off SIL safety functions
- Siemens Scalance Network and Wireless Implementation
- GPS Ferry positioning system
Service Support & Frameworks
In order to further support our customers, we offer tailored service and framework agreements comprising routine PPMs and emergency 24/7 365 day response. Dependent upon specification, our systems are supplied with the ability to be remotely accessed, especially in the waterways sector, as assets are often located in hard to reach area’s – some even becoming inaccessible under certain conditions.