WFI circuit: Increasing security and saving operating costs with local control loops of valves and sensors

If too much WFI is taken out of the loop it results in unnecessary additional costs. Diaphragm valves can be used to regulate WFI extraction because they comply with the demanding legal hygiene standards in the pharmaceutical industry. The problem is that they are rather imprecise. To compensate for this, expensive and heavy control actuators are often designed specifically for this task.

Target

Control behaviour (actual)

Constant monitoring of the WFI loop is intended to secure production processes and guarantee system availability – all with the least possible human effort. At the same time, it serves to comply with the a number of rules and regulations in the pharmaceutical industry, which require complete documentation of the measurement parameters to produce clear traceability.

To control WFI flow rates at tapping points, conventional systems often use Coriolis measuring devices, but these are usually expensive to purchase and operate. Because they reduce pipelines, they also increase pumping costs. In addition, their size and weight make them cumbersome to install.

The speed and temperature in a WFI loop should always correspond to the guidelines so that no harmful biofilms can settle in the pipelines. It would contaminate the purified water and thus the pharmaceutical products. This is why flow rate and temperature sensors monitor the process. Ultrasonic clamp-on sensors are often used in conventional applications, but they require extensive calibration work, and are prone to errors and are relatively imprecise.

Temperature

Speed

Treatment and storage of water for injection is especially beneficial when it comes to operating costs. As such, daily WFI consumption is measured as precisely as possible. In addition, conclusions can be drawn about possible errors or defects in certain process steps in case the daily consumption is unusually high. Measuring is often done with the help of ultrasonic clamp-on sensors, but they are prone to errors, so determining exact daily quantities is difficult with them.

Flowmeters, temperature sensors, control valves and other components are often installed in hard-to-reach places in a system or a machine. The devices are also usually large and heavy. These factors usually complicate both the installation and subsequent maintenance in day-to-day production.

Bürkert regulation solutions exactly match each customer’s requirements. A local control loop for extracting ultrapure water for the production process ensures extremely precise water dosing in conjunction with individually designed components. Thanks to swift reaction times, the valve can immediately activate in case of an unwanted process deviation. Excessive doses are thus a thing of the past, while system efficiency increases.

Process control

Position control of the valve

Set-point value

For applications that require highly precise control and where compressed air is not available or is undesirable, valves driven by electric motors offer a perfect solution. A higher resolution lets the closed-loop control be more precise than with pneumatically operated valves. Nearly seamless activation of the valve allows very precise regulation of the flowing WFI, which prevents an over-shoot when activating the control valve.

Conventional valve        Pneumatic diaphragm control valve Type 2104        Electromotive diaphragm control valve Type 3363

Target

Control behaviour (actual)

Most precise regulation without over-shoot

Power is required to create compressed air – and that costs money. Conventional valve technology requires a constant supply of compressed air in order to regulate the steam supply through the process valve and thus ensure precise control of the WFI. By contrast, Bürkert uses solenoid valve technology, which only consumes compressed air when the valve position needs to change. This considerably reduces energy consumption and therefore operating costs.

Compressed air consumption nozzle flapping plate principle

Compressed air consumption Bürkert solenoid valve principle

Movement

When manufacturing pharmaceutical products, the exact regulation of the WFI circuit and documentation of the corresponding parameters are specified. However, extraction processes from the WFI loop can only be precisely controlled if the control valves are designed appropriately. Bürkert provides assistance here so that, with the proper dimensioning, the stroke range of the valve is optimally utilised and a sufficient flow reserve is ensured.

           Valve is too small                            Valve is optimal                             Valve is too large

Cv value (Cv)

Flow rate (q)

Stroke range

Flow reserve

Bürkert engineers developed FLOWave to help you carry out hygienic, high-precision flow rate measurements. Thanks to our innovative SAW technology, volume flow and temperature can be determined without any sensor elements in the measurement tube – regardless of the conductivity of the media. The new type of measurement within the pipe is particularly precise, eases integrated into the WFI loop, and minimises the risk of contamination: There is no contamination in areas with no dead space.