The unique characteristics and efficiency of proportional solenoid valves make them an excellent option for medical applications requiring precise electronic flow or pressure control. These 2-port valves are available in a variety of sizes and pressure settings, and are designed for excellent repeatability and resolution with fast response to changes in the current applied to the solenoid.
Breaking Down the Mechanics of Proportional Valves
Proportional valves are used to control pressure and flow. These devices produce a precise output in response to a controlled electronic input. They are coupled with flow or pressure sensors to provide precise flow rates or pressure settings. These are “closed loop” systems that use electronics to adjust the valve to meet exact requirements in both static and dynamic applications.
The solenoid receives input current (amperage) signals and uses the electromagnetic field of a coil to precisely move an armature, allowing the valve to correspondingly adjust it’s output flow. That allows the user to precisely control downstream flow and pressure.
A pneumatic proportional valve can control several variables, including:
Humphrey Products ProControl Valve Series are used by clients to accomplish three kinds of variable output flow control:
- Dynamic Control: Flow continuously adjusts within a single cycle (closed-loop responses)
- Incremental Control: Predetermined changes within each cycle (ie reduce flow at cycle end)
- Selectable Control: Prescribe an output flow that can vary from cycle to cycle, or job to job.
Finding a Proportional Valve
A proportional valve is a good fit for medical devices because it’s a simple and relatively inexpensive solution that produces precise flow or pressure in a variety of functions. When selecting a proportional valve for a medical device, consider the medium to be controlled first. Valve materials in the flow path must be compatible with the gas (O2, N2, CO2, air, etc).
Next, determine application parameters for the valve, such as:
- Inlet pressure and maximum controlled output pressure
- Required flow range
- Media temperature and ambient temperature
- Environmental factors, including location (hospital, clinical or portable), weight and space restrictions
- Power consumption, especially for portable or mobile applications
Medical Device Valve Applications
Medical proportional valve applications include:
- Anesthesia and ventilator gas mixing
- Ventilator patient delivery for controlled breathing
- Leak testing for medical components and packaging
- Positive End-Expiratory Pressure (PEEP) control
- Oxygen concentrators
- Patient simulators
- Clinical diagnostic equipment