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Integrity test of an ultrafiltration membrane

Integrity test in ultrafiltration

An ultrafiltration system is a standard component in industrial water treatment, and the central component are the membranes. If they start to leak, contaminants will make their way into the filtrate. You need to monitor the differential pressure between inlet and outlet closely in order to identify leakages as early as possible. Festo recommends automated, decentralized pressure control and pressure monitoring for this function.

Automated testing and control

Ultrafiltration systems and/or membrane filtration can be found in both waterworks and in industrial water treatment. The pressure retention test is a proven method to test the filter integrity and it is important to carry it out regularly in order to prevent contamination of the filtrate. In this test, controlled compressed air is applied to the individual membrane modules for two to three minutes and the pressure drop is measured. If this deviates from a reference value, this indicates leakage in the membranes.

The integrity test can be automated in a way that these days, is as reliable as the pressure retention test itself. The key to this is the CPX/MPA system from Festo as a remote I/O with integrated pneumatics. It allows you to record the pressure in the air hoses over an analog input card with a direct supply port, giving you an accurate leak test.

The CPX/MPA is installed directly in the field and can be connected simply to the central controller using standard fieldbus protocols. In addition, this dispenses with almost the complete cabling effort. Continuous process monitoring, even remotely, is possible, as is the protection of the pressure controller against operational error and manipulation.

We will show you the benefits over manual or semi-manual testing. To bypass this, go directly to the Festo solution.

Filter integrity test efficiency comparison

Disadvantages of the manual process

In many cases, the pressure retention test is still carried out manually, which has been the conventional solution. Here, all pneumatic valves are opened and closed manually. The applied pressure has to be set manually as well. Recording, evaluation and monitoring are also done by hand. This approach however, has significant disadvantages. Alongside the personal effort required, there is the laborious data acquisition. On top of that, the process is prone to error and is difficult to integrate in the control system.

Intermediate solution: Semi-automated process

Some water treatment plants are already semi-automated. In this case, many of the pressure retention test steps no longer have to be triggered and executed manually. The pressure value measurements are done automatically through a PLC. However, pressure adjustment and regulation generally still have to be done by hand.

Advantages of an automated solution

Complete automation, such as that offered by Festo with CPX/MPA, is integrated easily at the PLC level through the cabling of the field devices to I/O cards. This means that all process steps are automated. Pressure control and measurement are done directly in the field through integrated functions.

Semi-automated pressure retention test process

Semi-automated pressure retention test process

Integrated CPX/MPA solution from Festo

Festo offers you a solution for ultrafiltration systems that integrates the pressure retention test as a function on the I/O system: The CPX/MPA, a modular electric terminal (CPX) with integrated pneumatics (MPA). The compact system is installed directly in the system and listens to the standard fieldbus protocols, making it easy to integrate in the primary centralized controller. Alternatively, a local autonomous PLC controller can also be created decentrally through the control module that is integrated in the CPX/MPA. In any case, the cabling effort is minimal. The system guarantees continuous process monitoring, even over remote access, and protects the pressure controller from operational error and manipulation.

The pressure query is done through an analog CPX-4AE-P-xx input card, which you use to measure the pressure in the air hose through a direct supply port. The setting defined in the PLC directly resets a proportional pressure control valve that is integrated on the CPX/MPA, so you don't need a separate control valve or a pressure sensor in the field. The solution also controls magnetic on off valves that prevent the ingress of raw water into the pneumatics, through integrated digital output cards on the CPX.

The CPX/MPA can even take on further functions from your system: Pilot valves for isolation process valves, analog output cards for control process valves, digital input cards for positional feedback from the process valves or analog input cards for process sensors.

Fully automated pressure retention test solution

Fully automated pressure retention test solution

Advantages of automation with CPX/MPA

Festo is an a position to offer an innovative solution for ongoing ultrafiltration integrity tests, through the combination of electrics and pneumatics in one I/O system. Both operating companies and water treatment system design engineers benefit in equal measure:

  • Integration: The direct connection of the pressure regulator, the pressure query and the digital outputs through a back wall bus, keep the cabling effort down to a minimum. A hose and an electric signal cable are only needed for the on off valve.
  • Safety: The pressure level is defined through the PLC. In comparison to manual pressure setting, this protects the system against operational error by system staff. Safety is increased even more if the CPX/MPA is installed in a closed control cabinet.
  • Efficiency: Reproducibility of the correct pressure setting is optimal.
  • Monitoring: A pressure query to individual membrane modules is possible without any problem, through terminals.
  • Autonomy: CEC as the decentralized PLC function facilitates an autonomous system that works reliably, even in the case of fieldbus errors.
  • Management: Data acquisition and evaluation are done simply in the primary PLC or decentrally through Festo SCADA on the CPDX. That also applies in the case of remote access over the Internet or the mobile phone network.

And as has been said already, the CPX/MPA can integrate additional solutions.