Why use a proportional valve?

Why use a proportional valve?

A proportional valve provides a change in output pressure or flow directly corresponding to the change in the input. For instance, doubling the input will result in doubling the output.

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Key Features of Proportional Valves

Proportional valves are ideal for applications requiring variable output pressure, either in steps or continuously. Stepped output pressure means the pressure stays at one level before moving to the next, while continuous output pressure gradually increases at a set rate.

These valves can interconnect, using the output from one as the input for another, and many come with programmable, onboard diagnostics, making them highly compatible with Industry 4.0 systems.

Reliable and cost-effective, particularly air-pilot operated types, they offer quick response times and consistent control.

Benefits of Using Proportional Valves

Proportional valves help reduce cycle times by quickly stabilizing pressure. Their fast and precise response improves efficiency, and their consistent control ensures predictable outcomes every time.

Selection Considerations

Key parameters include:

• Type of variable: Pressure, flow, or another characteristic.
• Required input and output pressure ranges and flow rates.
• Operating temperature and environmental conditions, such as the presence of moisture or dirt.

Determine whether the process is static, step-by-step, or dynamic, as this dictates the need for specific response times and hysteresis performance. While cost is a factor, air-pilot operated valves offer a budget-friendly option.

Typical Applications

Proportional valves find use in analytical and test instruments, and process applications like tensioning, spraying, and blow molding. They're also used in medical and foundry applications, along with numerous other fields. For specific inquiries, feel free to contact us.

Industrial Applications of Proportional Valves

Many industrial applications utilize proportional solenoids for controlling hydraulic pressure and flow. These valves are designed for both mobile and industrial settings.

The terms pressure differential and pressure drop are often used interchangeably, referring to a difference in pressure. Proportional valves are typically rated for nominal flow at certain pressure differentials. However, actual systems rarely have exact differentials, necessitating a tailored valve size.

In industrial applications, proportional valves meter flow in and out of actuators to provide precise control. The flow rate through the valve is proportional to the square root of the pressure differential.

For example:

If QRATED is 10 lpm at ΔpRATED = 10 bar, then QACTUAL will double if ΔpACTUAL is increased by a factor of 4.

Conversely, pressure differential is proportional to the square of the flow rate. If the flow rate is halved, the pressure differential is reduced to a quarter.

Proper valve sizing maximizes actuator performance. Practical experience shows that the optimal point for this differential occurs at about one-third of the system's maximum pressure. For instance, with a system pressure of 150 bar and 100 bar applied on the load, the remaining 50 bar drives the valve flow.

Using an energy-efficient approach, one might consider a valve producing 200 lpm at 50 bar. However, smaller valves respond quicker to input changes, offering greater control even if less energy-efficient.

Proper sizing ensures optimal performance, and resources such as IFPS Electronic Controls Specialist Certification and Study Manual offer detailed guidance for advanced users.

Test Your Skills

1. When the inlet pressure to a proportional valve is doubled with no change to the outlet pressure, the resultant flow will be:

• a. reduced by 50%
• b. the same
• c. doubled
• d. increased by 141%
• e. increased by 400%

2. Increasing the Δp through a valve beyond 1/3 of the available system pressure:

• a. increases the power available to the actuator
• b. decreases the power available to the actuator
• c. causes the actuator to reverse
• d. has no effect on the system
• e. reduces the heat load in the system

See the Solutions

1.d, 2.b

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