How to replace Solenoid Valves with AMF’s Rotary Valves?

Solenoid valves are commonly used in various industrial applications for fluid control, including water, gases, and aggressive media. They operate by using an electric coil to generate a magnetic field, which moves a plunger to control the flow of fluid. Despite their widespread use, solenoid valves have limitations that affect the efficiency and reliability of microfluidic systems, especially in demanding applications requiring precise fluid control.

AMF’s rotary valves offer an interesting alternative for a lot of applications. Designed with low internal volume and high chemical compatibility, rotary valves provide precise control without the common issues associated with solenoid valves. They are ideal for applications requiring reliable and efficient fluid management in compact spaces. By replacing solenoid valves with rotary valves, industries can achieve better performance, reduced maintenance, and improved process efficiency.

Solenoid Valves in microfluidic applications

There are various types of solenoid valves, including one- or two-solenoid valves, direct current (DC) or alternating current (AC) powered, and those with different numbers of ways and positions. These valves are widely used across industries for applications such as general on-off control, calibration and test stands, pilot plant control loops, process control systems, and various original equipment manufacturer (OEM) applications.

Focus on 2/2 Solenoid Valves

These valves are designed for binary flow control, either allowing or stopping the flow of media. They are direct-acting and typically used in applications where simple on/off control is required. The valve consists of a body, solenoid coil, plunger, and seal materials like FKM or EPDM. When energized, the coil generates a magnetic field that moves the plunger, enabling flow. When de-energized, a spring returns the plunger to stop the flow. These valves are ideal for applications that demand reliable and rapid shutoff capabilities.

Limitations of Solenoid Valves

Volume displacement: The opening and closing cycles of solenoid valves cause volume displacement, resulting in pressure fluctuations. These fluctuations can lead to inconsistencies in flow rate, affecting process efficiency and product quality, particularly in precision-driven applications such as molecule to molecule interaction where one would track single events..

Internal volume and dead volume: Solenoid valves typically have large internal volumes, ranging from 54 µL to 100 µL. This large internal volume can increase dead volume, raising the risk of contamination and inefficient fluid management. Higher internal volume also leads to greater sample and reagent usage, increasing operational costs and reducing measurement accuracy.

Non-linear fluidic path: Unlike the schematic representations that suggest a straight path, solenoid valves typically feature several turns within the fluidic path (usually two 90° angle). These bends create obstacles, leading to turbulence and potential dead volumes where fluids can stagnate.

Droplet issues: In solenoid valves, droplets may collide or merge at these corners, disrupting the flow and potentially leading to inaccurate results. The non-linear flow path can also cause variations in flow speed, which is especially problematic in precision applications.

Flow inconsistencies: The irregular flow path in solenoid valves can result in uneven liquid circulation, leading to inefficiencies and inconsistent fluid management.

Heating issues: Continuous operation of solenoid valves (ie. maintaining the channel open)  generates significant heat due to the constant electric current running through the coil. This heat can negatively impact the valve’s performance and longevity, potentially leading to thermal expansion and seal failure. Additionally, the heat can compromise the integrity of heat-sensitive samples, such as biological cells or temperature-sensitive chemicals, causing stress or degradation that affects the accuracy and reliability of experimental results or industrial processes.

Power consumption: Solenoid valves need a constant power supply to remain open, which results in higher energy consumption. This can be a significant drawback in energy-sensitive operating contexts.

Material compatibility: Solenoid valves must be compatible with the media they control. Exposure to aggressive chemicals or high-temperature fluids can degrade materials like FKM or EPDM, leading to premature valve failure and potential safety hazards.

Solenoid Valve replacement with AMF’s Rotary Valve

Replacing solenoid valves with AMF’s rotary valves can significantly enhance performance and reliability in various industrial systems. Rotary valves, such as the RVM series, offer precise control and durability, addressing many limitations of solenoid valves. These valves are ideal for handling water, gases, and chemicals in demanding environments.

AMF’s rotary valves are designed to handle a wide range of media, including chemicals, steam, and air. They provide precise control and are capable of operating under various pressures and temperatures, ideal for demanding industrial environments. They feature a compact design, reducing the risk of clogging and internal volume issues. Their ability to maintain a closed position under high pressure makes them a reliable choice for critical applications, offering improved safety and performance over traditional solenoid valves.

2/2 Solenoid Valve replacement with On/Off Rotary Valve

2/2 Solenoid Valve overview

A 2/2 solenoid valve is a direct acting valve that operates with two ports—an inlet and an outlet—and two positions: open and closed. It’s controlled by an electromagnet that moves a plunger to either allow or stop the flow of fluids or gases.

On/Off Rotary Valve overview

An On/Off rotary valve uses a rotating mechanism to control the flow, providing precise control with extremely low internal volume and better fluid management.

Application example: Enhancing molecular analysis with Rotary Valves

In a real-life application, the goal was to analyze and detect molecules on a microfluidic chip. The setup initially used two 2/2 solenoid valves—one controlling the solution A inlet and one controlling the solution B inlet.

Both solutions were injected in a Y-shaped microchannel and the flow was to be stopped to enable the measurement of molecule-to-molecule interactions.

However, when stopping the flow by closing the two 2/2 solenoid valves, parasitic backflow led to volume displacement within the chip and ultemaltey to increased background signal. This negatively impacted the accuracy and quality of the measurements.

After replacing the two 2/2 solenoid valves with AMF’s rotary valves, the setup experienced no background signal, no parasitic backflow, and no volume displacement upon closing the On/Off valves, significantly improving the precision and reliability of the results.

Additionally, there was a desire to switch from solenoid valves to AMF’s rotary valves due to carryover issues. With solenoid valves, a significant volume of sample (50 to 100uL) needed to be pushed through the system to ensure no contamination between runs. This requires a large volume of sample in order to be certain that theres is no sample-to-sample contamination. In contrast, rotary valves, with their much lower internal volume (3uL), eliminated these contamination problems, leading to a dramatically reduced sample volume.

As these molecule interaction studies are mostly used in the pharma industry where the sample can be scarce and expensive, a smaller sample volume requirement leads to significant decrease in the overall costs of the measurement making the instrument more competitive.

Solenoid Valve limitations

Solenoid valves have several limitations. Their binary operation restricts fine control, leading to limited precision. They also have a larger internal and dead volume, increasing inefficiencies, carryover, and the risk of contamination. The non-linear fluidic path with two 90° bends creates obstacles, leading to turbulence, potential dead volumes, and flow inconsistencies. Droplets may collide or merge at these corners, disrupting flow and causing inaccuracies. The actuation process can also cause volume displacement (parasitic backflow), resulting in pressure instability. Additionally, continuous operation generates heat, degrading valve components and negatively impacting heat-sensitive samples, such as cells, potentially compromising experimental accuracy and reliability.

Advantages of Rotary Valves:

In contrast, rotary valves address these issues effectively. They provide enhanced control over fluid flow, allowing for more accurate adjustments and better process management. Their design features a lower internal volume, minimizing carryover and dead volume, which leads to more efficient fluid management and reduces contamination risks. The fluidic path in rotary valves is linear and unobstructed, eliminating the turbulence and dead volumes associated with solenoid valves, and ensuring smooth, consistent flow. Rotary valves also prevent issues like volume displacement and parasitic backflow, ensuring stable pressure and flow conditions.

Furthermore, rotary valves generate less heat during operation, contributing to consistent performance even in high-temperature environments and extending the valve’s service life. This also makes them a safer option for applications involving heat-sensitive samples, preserving the quality and reliability of the outcomes. The simplified, straight fluid path also prevents droplets from merging or getting trapped, ensuring homogeneous circulation of the liquid, which is crucial in precision applications.

Impact of switching to Rotary Valves

• Technical improvements: Replacing solenoid valves with rotary valves results in significantly enhanced precision and stability in fluid management. The lower internal volume of rotary valves minimizes carryover, ensuring higher accuracy and preventing contamination while using smaller quantities of sample.

• Improved fluid control: Rotary valves provide more precise control over fluid flow, eliminating issues like parasitic backflow and volume displacement that are common with solenoid valves. This results in better measurement accuracy and consistency in processes where precision is crucial.

• Streamlined fluid path: Rotary valves offer a streamlined, unobstructed fluid path, which eliminates turbulence and prevents droplets from merging or getting trapped. This ensures a smooth, homogeneous flow, further enhancing the precision and reliability of fluid management.

• Enhanced reliability: Rotary valves offer a more robust design, reducing the risk of valve failure. Their ability to handle a wide range of media, including aggressive chemicals, without compromising performance, makes them more reliable over extended periods.

• Operational efficiency: Although rotary valves are larger than solenoid valves, they typically consume less power, which can lead to lower overall energy costs. More importantly, rotary valves generate significantly less heat during operation, which helps protect heat-sensitive samples from thermal damage.

• Protection of heat-sensitive samples: Rotary valves generate less heat during operation, making them a better choice for applications involving heat-sensitive samples, such as live cells. This helps prevent thermal stress on samples, ensuring the integrity and accuracy of experimental results.

Conclusion

Switching from 2/2 solenoid valves to AMF’s On/Off rotary valves is not just about upgrading features—it’s about transforming your entire fluid management process. With rotary valves, you achieve unparalleled precision, drastically reduce sample usage, and eliminate contamination risks, all while maintaining the integrity of heat-sensitive samples. This leads to higher reliability and lower operational costs, ultimately enhancing the quality and efficiency of your processes. In demanding industrial applications, these improvements are crucial for staying competitive and ensuring long-term success.

Reference:

https://iopscience.iop.org/article/10.1088/0960-1317/16/5/R01