Air Consumption in a Pressure Regulator: Exhaust, Bleed & Leakage Explained

Do pressure regulators consume air? The answer depends on the regulator design and operating conditions. Air can leave a pressure regulator through normal exhaust, intentional bleed, or unintended leakage.

Understanding the difference between these three types of air consumption is important when selecting a pressure regulator, particularly for applications involving compressed air, inert gases, specialty gases, or systems where minimizing air consumption is important.

In a typical pneumatic pressure regulator, there are three primary ways air or gas can escape:

• Exhaust or relief
• Designed-in bleed
• Unintended leakage

Although each results in air leaving the system, they occur for very different reasons.

What Is Pressure Regulator Air Consumption?

Pressure regulator air consumption is the amount of compressed air or gas that leaves a regulator through intentional bleed, pressure-relieving exhaust, or unintended leakage.

Not every pressure regulator continuously consumes air. The amount of air consumption depends on the regulator’s design, whether it is relieving or non-relieving, and the requirements of the application.

Precision regulators, for example, may intentionally consume a small amount of air to improve pressure sensitivity, accuracy and repeatability.

Understanding where the air is going is the first step in determining whether air consumption is normal or indicates a problem.

What Causes Air to Escape From a Pressure Regulator?

Air generally leaves a pressure regulator in three ways: exhaust, bleed and leakage.

These terms are sometimes used interchangeably, but they describe different conditions.

Pressure regulator air consumption can result from normal exhaust, designed-in bleed or unintended leakage.

Pressure Regulator Exhaust

Exhaust is the normal release of downstream pressure to atmosphere when pressure rises above the regulator setpoint or when the regulator is adjusted to a lower pressure.

This is a normal function of a relieving pressure regulator.  When the regulator is in a steady state condition, and there is still some exhaust, it maybe do to a damaged valve seat.  In some precision regulators, there will be a very small amount of air coming from the exhaust port.  This is intentional to put the regulator into a dynamic state to make the regulator more sensitive.

For example, if a regulator is maintaining 60 psig downstream and the regulator is adjusted to 40 psig, a relieving regulator can vent excess downstream pressure until the new pressure setting is reached.

A non-relieving pressure regulator, on the other hand, does not automatically vent downstream pressure to atmosphere.

When using a non-relieving regulator, downstream pressure must be reduced through normal system flow or by another pressure-relief device.

In applications where releasing air or gas directly into the surrounding environment is undesirable, a regulator with a tapped exhaust port can allow the exhaust to be captured and routed to an appropriate location.

What Is Bleed in a Pressure Regulator?

Bleed is a small, intentional and continuous flow of air incorporated into the design of some pressure regulators.

It is particularly common in certain precision pressure regulators.

The controlled bleed allows the regulator to continuously respond to very small pressure changes, which can improve:

• Pressure accuracy
• Sensitivity
• Repeatability
• Response to changing system conditions

This air typically exits through a small bleed orifice or through the regulator’s exhaust port.

Because the bleed is intentionally designed into the regulator, a small continuous airflow does not necessarily mean the regulator is leaking or malfunctioning.

This distinction is particularly important when troubleshooting precision pneumatic systems.

What Is Pressure Regulator Leakage?

Leakage is unintended air or gas escaping from a pressure regulator through internal valve seats, relief seats, seals or external connections.

Ideally, leakage would be zero. In actual pneumatic components, however, manufacturing tolerances, sealing materials, elastomer compression and regulator design can result in a small amount of allowable leakage.

Potential leakage paths include:

• Relief valve seats
• Main valve seats
• Diaphragm seals
• O-rings and other elastomer seals
• Threaded connections
• External body seals

The acceptable amount of leakage depends heavily on the application.

A small amount of leakage that is acceptable in a general industrial compressed-air application may not be acceptable when controlling an expensive specialty gas or in an application requiring extremely low leakage.

Exhaust vs. Bleed vs. Leakage

These three terms describe very different types of pressure regulator air consumption:

The important distinction is that exhaust and bleed can be normal regulator functions, while leakage is unintended.

Relieving vs. Non-Relieving Pressure Regulators

One of the most important considerations when evaluating regulator air consumption is whether the regulator is relieving or non-relieving.

Relieving Pressure Regulator

A relieving regulator can vent excess downstream pressure through its exhaust.

If downstream pressure rises above the regulator setpoint—or the pressure setting is reduced—the regulator can automatically relieve the excess pressure.

Non-Relieving Pressure Regulator

A non-relieving regulator does not vent downstream pressure to atmosphere.

If downstream pressure rises above the setpoint, the pressure must be reduced through downstream consumption, system flow or a separate relief device.

Non-relieving regulators can be advantageous when the regulated media should not be released into the surrounding environment.

Do Precision Pressure Regulators Consume Air?

Some precision pressure regulators intentionally consume a small amount of air through a designed-in bleed.

This controlled airflow can help the regulator respond to extremely small changes in pressure and provide greater sensitivity, accuracy and repeatability.

However, not all precision regulators have the same air-consumption characteristics.

When compressed-air consumption, gas cost or environmental considerations are important, regulator bleed specifications should be considered during product selection.

A regulator with some designed-in bleed should therefore not automatically be ruled out. The required pressure-control performance should be considered alongside the amount and cost of the gas being consumed.

Why Is My Pressure Regulator Leaking Air?

Air coming from a pressure regulator does not always indicate a leak.

Before assuming that the regulator has failed, determine where the air is coming from and under what operating conditions it occurs.

Air coming from the exhaust port may be normal if:

• Downstream pressure has risen above the setpoint.
• The pressure setting was recently reduced.
• The regulator incorporates an intentional bleed.
• Downstream equipment is creating pressure that must be relieved.

Air escaping continuously from an external seal, fitting or unintended location may indicate actual leakage.

If air consumption is unexpectedly high, inspect connections, seals and operating conditions and compare the regulator’s performance with the manufacturer’s specifications.

How Can Pressure Regulator Air Consumption Be Reduced?

Several regulator design options can help minimize air or gas consumption.

Use a non-relieving regulator when appropriate.
A non-relieving design prevents the regulator from intentionally exhausting downstream pressure.  These are usually used in steady flow applications.

Select a low-bleed regulator.
If precision regulation is required, compare the bleed or air-consumption specifications of available models.

Consider soft valve or relief seats.
Special sealing designs can help reduce leakage across regulator seats.

Use a tapped exhaust.
A tapped exhaust port allows exhaust or leakage through the relief seat to be captured and routed to another location.

Consider bubble-tight regulator designs.
Applications requiring extremely low leakage may require special sealing materials and manufacturing processes designed to achieve bubble-tight shutoff.

Properly size the regulator.
Selecting the appropriate regulator for the required pressure and flow can improve system performance and help avoid unnecessary pressure-control problems.

Why Air Consumption Matters

Minimizing unnecessary compressed-air consumption can improve overall pneumatic system efficiency.

Air consumption becomes particularly important when the regulated media is:

• An inert gas
• Nitrogen
• Specialty or expensive gas
• Process gas
• A gas that should not be released into the surrounding environment

In these applications, regulator selection should consider not only pressure and flow requirements but also bleed rate, leakage specifications and exhaust characteristics.

How Do You Select the Right Pressure Regulator?

When selecting a pressure regulator, consider more than inlet pressure, outlet pressure and flow.

Important factors include:

• Inlet and outlet pressure range
• Required flow capacity
• Pressure accuracy
• Sensitivity and repeatability
• Relieving vs. non-relieving design
• Bleed or air-consumption rate
• Allowable leakage
• Media compatibility
• Materials of construction
• Exhaust requirements
• Operating temperature

The correct regulator is the one that provides the required pressure-control performance while meeting the application’s allowable air or gas consumption.

Frequently Asked Questions About Pressure Regulator Air Consumption

Do pressure regulators continuously consume air?

Not necessarily. Some precision pressure regulators intentionally use a small continuous bleed to improve sensitivity and pressure-control performance, while other regulators have little or no designed-in continuous air consumption.

Why does a pressure regulator exhaust air?

A relieving pressure regulator exhausts air when downstream pressure exceeds the regulator’s setpoint. This may occur because downstream pressure increased or because the regulator was adjusted to a lower pressure setting.

Is air coming from a pressure regulator normal?

It can be. Air from the exhaust port may be normal pressure relief or intentional bleed. Continuous air escaping from an unintended location may indicate leakage.

What is the difference between bleed and leakage in a pressure regulator?

Bleed is an intentional airflow designed into certain regulators to improve performance. Leakage is unintended air or gas escaping through seals, valve seats or other components.

What is a non-relieving pressure regulator?

A non-relieving pressure regulator controls downstream pressure without automatically venting excess downstream pressure to atmosphere. Excess pressure must be removed through system flow or another relief method.

How can I reduce pressure regulator air consumption?

Select a regulator with appropriate bleed characteristics, consider a non-relieving design where suitable, use low-leakage or special sealing options when required, and properly size the regulator for the application.

Need Help Selecting a Pressure Regulator?

The appropriate pressure regulator depends on the application’s pressure range, flow requirements, accuracy, media and acceptable level of air consumption.

ControlAir offers a wide range of pressure regulators and precision pressure regulators for pneumatic and process applications. Contact ControlAir for assistance selecting the appropriate regulator for your application.