What are the applications of proportional valve?

Selecting a Proportional Valve for Medical Applications

Medical Device Valves

Proportional solenoid valves are highly efficient and ideal for medical applications that require precise electronic flow or pressure control. These 2-port valves come in various sizes and pressure settings, offering excellent repeatability and resolution, with quick responses to changes in solenoid current.

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The Mechanics of Proportional Valves

Proportional valves control both pressure and flow by producing a precise output in response to an electronic input. Coupled with flow or pressure sensors, these valves offer exact flow rates or pressure settings. These "closed-loop" systems use electronics to adjust to specific requirements in both static and dynamic applications.

The solenoid receives input current signals and employs an electromagnetic coil to precisely move an armature, allowing the valve to adjust its output flow accordingly. This enables precise control of downstream flow and pressure.

A pneumatic proportional valve can manage several variables, such as:

• Force
• Position
• Temperature
• Level

Humphrey Products’ ProControl Valve Series supports clients in three key types of variable output flow control:

• Dynamic Control: Continuous flow adjustment within a single cycle (closed-loop responses)
• Incremental Control: Predetermined changes within each cycle (e.g., reducing flow at the cycle’s end)
• Selectable Control: Variable output flow from cycle to cycle or job to job

Finding a Proportional Valve for Medical Devices

Proportional valves are suitable for medical devices as they offer a simple and cost-effective solution for precise flow or pressure control in various functions. When choosing a proportional valve for a medical device, start by considering the medium to be controlled. Ensure that the valve materials are compatible with the gas (O2, N2, CO2, air, etc.) in the flow path.

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

Medical Device Valve Applications

Proportional valve applications in medical devices 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

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Medical Device Valves From Humphrey Products

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

Proportional Valve Types for Different Applications

Proportional valves are versatile and suitable for various applications in machinery, basic processes, and hydro-pneumatic systems. They offer compact and cost-effective solutions for controlling low flow rate pressure or flow.

Given the variety and sources of supply, selecting the correct proportional valve is crucial. This article outlines important considerations for choosing the appropriate proportional valve.

Proportional Valve Set Points

Key considerations include:

• The maximum and minimum pressures the valve may encounter
• The flow ranges the valve may experience

Static Set Point

Fixed Pressure or Flow with Infrequent Changes

Typical Applications:

• Spot welding: Controls pressure to a cylinder that applies pinching force, with pressure set based on material type and thickness until setup for a different material
• Leak testing: Applies fixed pressure to check component soundness, adjustable for different applications

Dynamic Set Point

High-Frequency Pressure or Flow Changes

Typical Applications:

• Pressure control valves in flight simulators: Constantly adjusts cylinder pressure to move the simulator cabin
• Material testing: Steadily increases valve pressure output until the material fails

Step-By-Step Point

Low-Frequency Pressure or Flow Changes

Typical Applications:

• Filling systems: Adjusts flow rate down as the container approaches the required fill level for final filling at a lower rate
• Gas control to a burner: Requires different gas flow rates based on heat requirements

Adjusting Set Points

Another consideration is how to adjust the setting—whether it’s a set pressure or flow rate. Set points can be static, dynamic, or 'step-by-step'.

• Some valves allow set point adjustments via an analog control signal over power cables or fieldbus communications
• Others offer a local interface
• Some enable PC communication through an RS 232 interface for tuning and optimization

Actuation of Proportional Valve Operation

Engineers should also consider the type of operation required. Different methods include:

• Proportional solenoids: Adjust valve position based on varying coil voltage, offering short response times and low hysteresis.
• Pulsed solenoids: Use small solenoid valves to load and unload pressure in a control chamber, allowing the valve to open and close.
• Piezoelectric elements: Ideal for portable and tabletop machines like medical equipment, with very low power consumption, operable by batteries or solar cells.
• Pneumatically operated with a positioner: Suitable for large capacities and flow rates, using a positioner as a pilot to enable large valve operation.

This article discusses key factors to consider when specifying and purchasing proportional valves. For more information, leave comments below, post a technical question in the Solution Centre, or email us at [email protected].

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