How do you choose a proportional valve?

Medical Device Valves

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 various sizes and pressure settings, and are designed for excellent repeatability and resolution with fast response to changes in the current applied to the solenoid.

For more information, please visit proportional hydraulic solenoid valve.

How Proportional Valves Operate

Proportional valves are integral in controlling pressure and flow precisely by responding to controlled electronic inputs. These devices are part of closed-loop systems that make use of electronic adjustments to meet both static and dynamic application requirements. The solenoid receives input current signals and uses an electromagnetic field to move an armature, thus allowing precise control of the downstream flow and pressure.

A pneumatic proportional valve can control several variables, including:

• Force
• Position
• Temperature
• Level

Humphrey Products ProControl Valve Series help clients achieve different types of variable output flow control:

• Dynamic Control: Flow continuously adjusts within a single cycle (closed-loop responses)
• Incremental Control: Predetermined changes within each cycle (e.g., reduce flow at cycle end)
• Selectable Control: Configure an output flow that can vary from cycle to cycle, or job to job

Criteria for Selecting a Proportional Valve for Medical Devices

When choosing a proportional valve for medical devices, key considerations include the medium to be controlled. Ensure that valve materials in the flow path are compatible with the gas (O2, N2, CO2, air, etc.).

Next, determine the 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

Applications of Proportional Valves in Medical Devices

Proportional valves are applied across various medical device functions, including:

• 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

Medical Device Valves from Humphrey Products

Explore our proportional solenoid valve inventory and contact us at 844-447-9009 or procontrolway@humphrey-products.com for assistance with proportional valve application and selection.

Understanding Proportional Valve Types

Proportional valve technology encompasses several operating methods, each suitable for different applications:

• Piezoelectric valves operate by deforming to open or close when voltage is applied, ideal for low power consumption needs.
• Pneumatic positioners act as pilots to control air entry or venting in a diaphragm or cylinder, opening or closing larger valves.
• Electrical motor-actuated valves utilize a linear actuator to manage valve position, varying in design dimensions and sizes.
• Pulsed air-piloted solenoids adjust pilot control chambers for air pressure regulation, advantageous for specific cost and power consumption needs.
• Direct-acting proportional solenoids manipulate pistons or spools directly by varying coil voltage, ideal for dynamic applications with robust performance requirements.

Static vs. Dynamic Applications

Static applications maintain a fixed pressure set point most of the time, ideal for systems like leak testing where pressure consistency is crucial. Conversely, dynamic applications continuously adjust the set point, demanding a durable valve capable of frequent changes, such as in material testing scenarios where pressure must incrementally increase until failure.

Pulsed Air-Piloted Solenoids

These valves control air pressure via pilot chambers, suitable for applications with fixed requirements. However, they may struggle with accuracy under dynamic conditions due to limited adjustment capabilities and reliance on pilot valve cycle rates.

Direct-Acting Proportional Solenoids

Best for dynamic environments, these solenoids offer superior performance with fewer components. They provide fine control, quick response times, and are less susceptible to wear, ensuring reliability and precision in demanding applications.

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