OVERVIEW

Application Overview

Our consultants worked with the University, FreFlo and stakeholder group including research technicians and engineers to understand and capture all the requirements for the new system. Based on this understanding we were able to provide a detailed system specification including hardware and software design, based around the prespecified NI platform but also incorporating additional hardware, sensors and safety features to ensure safe operation.

The specification was then shared with the stakeholder group for review and validation before any work was undertaken, ensuring that, once begun, the project delivery was able to progress efficiently and without the need to accommodate further change requests that can add both cost and time to a project.

The scale of the system and the volume of the water being controlled means the design of safeguards are essential to minimise risks and keep the system safe whilst in use. The imposing project is responsible for controlling the flow of up to 200 litres per second, from two large constant head tanks each fed by a large storage tank with overflow system, into a stilling tank before entering a large test cell 45m long by 5m deep by 6m wide, capable of containing up to 1350 m³ of water. The flow of water through the tanks is used to test a variety of environmental and infrastructure materials and features. From the test tank, the water flows into two sump tanks, from where two large pumps circulate it back to the storage and header tanks.

The flow control system is critical for safe operation and is responsible for controlling the user set flow rate from the constant head tanks while maintaining the required water level in the sump area, refilling loops and the header tanks.

The custom algorithms controlling the sump pumps need to balance and maintain a constant flow of water back to the storage tanks to ensure that the tanks can maintain a constant head of water. The algorithms also need to ensure that there are no sudden changes in flow rate to avoid undue mechanical shock to the pipe mounts.

Each constant head system requires its own control system that can be operated independently of each other, with its own dedicated PC. This configuration allows two experiments to run independently. When there is a requirement for the system to be configured as a combined large-scale test bay, both systems are controlled via a single PC with the second PC available in a viewing mode only.

When in the single system mode, a sluice gate in the sump area must be opened to allow both systems to drain evenly. In addition to this, a pair of balancing valves in the sump return pipes must be opened; this is done automatically by the control system. Using flow meters on the sump return pipes, the four sump pumps are controlled in a coordinated manner.

Software

ICAIR User Interface

Using NI LabVIEW our consultants were responsible for the design, development and deployment of the control system software. The system provides access, control and safety management, test configuration and scripting, reporting and data logging, as well as system alarms and warnings.

Permissions Based Access

The control system software is designed as a series of modules. Access to configure and perform the various system functions is restricted via password-controlled permissions based on ‘operator’ ‘supervisor’ and ‘administrator’ profiles.

Test Setup

The automated test routine is the key feature of the control application. A user-friendly graphical user interface allows users to create, edit and save an unlimited number of test profiles. A test profile can be configured to varying timed flow setpoints that can be selected and executed.

The flow setpoint is, in fact, four separate setpoints, one for each valve/flow meter from the constant head tank. As not all the control valves are not equal in size, the maximum and minimum set points for each control valve is fixed in the software. To assist the user in setting up the correct desired total flow rate, the total aggregate flow that will be achieved based on the user inputs is displayed on screen.  It is also possible for a test profile to select which control valves are in use for a test. The minimum being one, the maximum is four. In the event of a full test being configured, involving both constant head tanks as one system, the user must select this option and then the aggregated total flow displayed is doubled to take both tanks into consideration. The user is still only able to set up four flow setpoints however the software automatically mirrors the settings to both systems.

A test profile is built up with the following parameters:

• Flow setpoints – one for each flow meter/control valve
• Stabilisation wait
• Dwell/delay time in seconds or wait for user input
• Fixed setpoint for spare digital out and analogue out signals
• As many flow set points as required by the user.

Error Handling

The application includes an integral error handling routine and dialogue that is if the user selects the errors status icon on the common system indicators bar. It includes a history of any errors reported by the system. Selecting an error provides more information about the error and suggests a possible resolution. It can only be cleared once the error has been resolved.

System Settings

The manual control screen and the test screens both allow the user to configure the systems setting and limit parameters without the need to change or update any of the application source code, thus making the system very flexible and configurable for not only commissioning and set up but also potential future expansion and changes.

The system manages the required soft start for the recirculation pumps and provides full closed-loop control of the sump pumps and control valves. Drop down options allow the user to enter separate settings for each system independently. Users are also able to set system directories for results logging, the logging rate up to a maximum of 500 Hz, and the scaling and conversion factors where applicable for the transducers. The software automatically adjusts the hydrostatic pressure measurements for the water viscosity based on the temperature measured by each of the submersible combined temperature and pressure sensors.

Alarms

A critical feature of the software system is to allow warnings and alarms to be set to protect both the valuable equipment and personnel. Each constant head system can be configured independently. The alarms include level warnings and level shutdown/abort limits for storage, sump and overflow tanks, pressure and temperature limits.

The system allows global email alerts to be set for both systems to notify alarm limits. All warnings and limits are downloaded and stored on each NI cRIO to ensure they are retained even after a power cycle.

In the event of a warning being detected the system illuminates the warning (Amber) beacon and sends a message to the PC Application. In the event of a limit being reached the system illuminates the alarm limit (Red) beacon, and sends a message to the PC Application, as well as invoking the “Safe Shutdown Engine” and sending an email to inform of the alarm and that action may be required.

The water level in the sump and storage tanks is safety critical. To prevent the tanks running dry and damage to the pumps or flooding and rupture, the system ensures that all sump pumps are automatically stopped immediately if the water level falls below the user set limit and that all control valves and end stop pumps are automatically shut down immediately once the tank reaches a user set limit.

The storage tank water temperature is safety critical. At 30 °C the bonding method of the tank begins to break down. If the storage tank water temperature rises to 26 °C, a warning is triggered. At 28 °C an automatic drain/refill procedure is executed to prevent tank failure. Any storage tank draining needs to be done in a manner that ensures the overflow drain is not flooded.

The valve positions are monitored within the alarm engine. Each valve has a method for flow proving. If a valve is opened but no flow occurs there will be an option to either alert the user or shut the system down.

Outcome

By using the flexible National Instruments framework, the system can be adapted or modified to meet future requirements thereby providing the University with an element of future proofing and greater return on this substantial infrastructure investment.

As part of the UK Collaboratorium for Research on Infrastructure in Cities, ICAIR hosts the National Distributed Water Infrastructure Facility (NDWIF); a unique laboratory for research into the performance of distributed urban water infrastructure. Together with the Urban Flows Observatory, these facilities position the University of Sheffield at the forefront of research into next-generation infrastructure.

ICAIR delivers state-of-the-art engineering testing capabilities designed to identify practical and efficient solutions for research collaborators and industry, meeting needs across the disciplines of construction, control engineering and infrastructure design, construction and operation.

• Provides unique experimental facilities for investigating interactions between above and below ground infrastructure and other capital-intensive national infrastructure assets.
• Brings the power of data, AI, robotics and advanced manufacturing to the field of infrastructure, to help increase productivity in the sector – a key target of the UK Industry Strategy.
• Is part of the water infrastructure theme of the “UK Collaboratorium for Research on Infrastructure and Cities” (UKCRIC), focused on making the nation’s infrastructure more resilient to extreme events and more adaptable to changing circumstances.
• Is designed to deliver translational research and development capacity in infrastructure construction and asset management to accelerate innovation within the construction industry and to broker long-term collaboration between innovation and technology providers and the infrastructure sectors.
• Provides a focus for interdisciplinary effort and expertise, state-of-the-art laboratories and technical facilities to generate world-class research on problems of relevance to infrastructure.