Where Is an Air Bellow Used in Papermaking?

An air bellow is mainly used in papermaking wherever a machine needs flexible pneumatic movement, controlled force, vibration isolation, or automatic position correction. Common applications include forming fabric and press felt guiding, fabric tensioning, guide-roll positioning, selected press and calender mechanisms, and other pneumatic adjustment systems around the paper machine.

Its role is particularly important where a rigid mechanical spring or fixed actuator would provide insufficient flexibility. By changing compressed-air pressure, an air bellow can provide smooth movement and adjustable force while absorbing part of the vibration generated by high-speed rotating equipment. Sun Hong Group supplies Paper Machine Rubber Air Bellow products and related pneumatic guiding components for different paper-machine positions.

What Does an Air Bellow Do on a Paper Machine?

A paper machine air bellow is a flexible reinforced-rubber pneumatic element. Compressed air enters the bellow and changes its height or supporting force, allowing it to move or position a connected roll, frame, or guiding mechanism. Unlike a conventional rigid pneumatic cylinder, the flexible rubber structure can tolerate controlled movement while also helping isolate vibration and mechanical shock.

In papermaking, this is useful because forming fabrics, press felts, dryer fabrics, rolls, and doctor systems operate continuously under changing tension and load. Paper-machine components also experience vibration, thermal expansion, moisture, and speed variation. A pneumatic bellow can respond to these changes without relying on a completely rigid mechanical linkage.

Its main functions can include:

The actual bellow design must match the stroke, load, pressure, mounting height, and surrounding machine structure.

Air Bellows in Forming Fabric Guiding Systems

One of the most common papermaking applications is automatic forming fabric guiding.

The forming fabric travels continuously around multiple rolls in the forming section. Even when the fabric and rolls are installed correctly, small differences in roll alignment, fabric tension, contamination, wear, or machine conditions can cause the fabric to move gradually toward one side.

If this lateral movement is not corrected, the fabric edge may rub against machine components. Continued deviation can damage the edge, distort fabric tension, create wrinkles, and shorten the service life of the clothing.

A pneumatic bellow guider solves this problem by combining a sensing element with a pneumatic actuator. The sensor detects fabric movement, while air pressure changes inside the actuator cause the guide roll to move slightly. Changing the roll angle guides the fabric back toward its normal running position.

Sun Hong's Paper Machine Pneumatic Bellow Felt Fabric Running Guider is designed around this principle. The pneumatic guider combines a signal sensor and actuator to control the guide-roll position and correct fabric deviation automatically.

The objective is not to make large movements. A properly operating guider makes small, progressive corrections so the fabric remains centered without being subjected to sudden lateral force.

Why Is Air Bellow Guiding Important for Forming Fabrics?

Forming fabric is one of the most important types of paper machine clothing because it supports the stock immediately after the headbox while allowing water to drain through its structure. Stable tracking is essential because the fabric may run continuously at high speed over many rolls and dewatering elements.

If the fabric moves repeatedly from side to side, several problems can develop. Edge abrasion may increase, machine-direction tension can become uneven, and the fabric may contact stationary machine structures. Poor tracking can also make operators increase tension unnecessarily in an attempt to stabilize the fabric.

A well-adjusted air bellow guider provides a controlled correction mechanism without requiring excessive clothing tension. The sensor identifies deviation, the pneumatic control changes actuator pressure, and the guide roll changes position sufficiently to steer the fabric toward the center.

Sun Hong's Paper Machine Clothing range includes forming fabrics, press felts, and dryer fabrics. These clothing products perform different functions, but all require suitable roll alignment, tension, guiding, and cleaning to maintain stable operation.

An air bellow therefore does not improve drainage directly. Its contribution is mechanical: it helps keep the clothing running in the correct position so the fabric can perform its intended forming or dewatering function.

Air Bellows in Press Felt Guiding Systems

Press felt guiding is another major application.

The press felt moves through the press section while carrying water away from the wet paper web and helping distribute pressure through the nip. The felt passes over multiple guide rolls, tension rolls, suction equipment, and press rolls. Because it operates wet and under substantial mechanical load, stable tracking is essential.

Uneven tension, roll misalignment, contamination, felt deformation, or changes in water distribution can cause lateral movement. If the felt runs too far to one side, the edge may wear rapidly or contact stationary components. Severe deviation can damage the felt or require an unscheduled paper-machine shutdown.

A pneumatic bellow guider responds to the felt edge position and changes the guide-roll angle. The movement should be gradual because aggressive correction can stretch or distort the felt. This is one of the advantages of pneumatic control: pressure can be adjusted to provide relatively smooth motion instead of abrupt mechanical correction.

The condition of the felt itself still matters. If a press felt has already become badly distorted or if a guide roll is mechanically misaligned, increasing air pressure is not a proper solution. Air bellow guiding should be part of a correctly aligned and maintained press section.

Air Bellows in Dryer Fabric Guiding

Dryer fabrics also require accurate tracking, particularly on long dryer sections containing many cylinders and guide rolls.

Unlike the wet forming and press sections, the dryer section operates at elevated temperature. Dryer fabrics repeatedly pass around heated cylinders while keeping the paper sheet in contact with the dryer surfaces. Thermal expansion, long running paths, roll alignment, fabric tension, and wear can all influence tracking.

A pneumatic guiding system can be used to make controlled corrections as the dryer fabric begins to move laterally. The operating principle is similar to forming fabric and press felt guiding, although the environmental conditions are different.

Temperature is particularly important. Rubber components, pneumatic hoses, sensors, lubricants, and seals need to be compatible with the installation location. A bellow selected for a cool wet-end application should not automatically be assumed suitable for a hotter dryer-section position.

For this reason, papermaking air bellows should be selected according to:

• Working temperature

• Fabric speed

• Required actuator movement

• Air pressure

• Guide-roll dimensions

• Machine width

• Available installation space

• Exposure to water, oil, and chemicals

The same basic pneumatic principle can therefore be used throughout the paper machine, while the actual component specification changes with the section.

Air Bellows in Felt and Fabric Tensioning Systems

Guiding and tensioning are related but different functions.

Guiding controls the lateral running position of the clothing. Tensioning controls how tightly the forming fabric, press felt, or dryer fabric is stretched around its roll path.

A fabric must have enough tension to maintain stable contact with rolls and dewatering equipment, but excessive tension can increase clothing wear, bearing loads, roll stress, and power consumption. Too little tension can cause slipping, wrinkles, poor tracking, and unstable machine operation.

Pneumatic bellows can be incorporated into tensioning mechanisms to move tension rolls or maintain force over a controlled range. As the clothing gradually stretches or changes dimension during service, the pneumatic system can compensate by changing the tension-roll position.

The main advantage is compliance. Rather than holding a completely fixed mechanical position, the air-supported system can maintain controlled force while allowing limited movement.

For tensioning applications, selection must consider:

A bellow that is correctly sized for a guider may not have enough stroke or load capacity for a tensioner.

Air Bellows Around Guide and Tension Rolls

Guide rolls and tension rolls are where pneumatic bellow movement is converted into useful machine adjustment.

In a guiding system, one side of a guide roll may move slightly so the roll axis changes relative to the direction of fabric travel. This small angular change produces a steering effect, causing the moving fabric or felt to shift laterally.

In a tensioning system, the entire roll may move toward or away from the clothing loop. Increasing that distance increases fabric path length and tension, while decreasing it reduces tension.

The air bellow itself therefore does not normally contact the paper or clothing. It acts through mechanical brackets, pivots, frames, or roll supports.

Good performance requires more than selecting the pneumatic component. The roll bearings, pivot points, brackets, shafts, and mounting geometry must move freely. If the tension roll is mechanically jammed, increasing air pressure may only overload the bellow without creating correct movement.

Maintenance teams should therefore inspect the complete mechanical assembly when a pneumatic guider or tensioner responds slowly.

Air Bellows in Press and Calender Applications

Some paper-machine press and calender mechanisms can also use pneumatic bellows for controlled support, movement, load application, or vibration isolation.

These positions normally require greater load capacity than a small clothing guider. The bellow may need a larger effective area, higher structural strength, or a double- or triple-convolution design to provide the required movement.

In press-related applications, the key requirement is stable and repeatable force. Uneven loading across the machine width can contribute to non-uniform pressing or mechanical wear. The pneumatic element should therefore operate within a controlled pressure range and suitable working height.

Calender equipment can present similar requirements because roll alignment and controlled loading influence paper surface treatment. In either case, the air bellow should not be selected only from outside diameter. Load, available stroke, installation geometry, temperature, and pressure all need to be defined.

Large-load applications are also where excessive side loading becomes particularly undesirable. Air bellows are designed primarily for axial compression and extension. Poorly aligned brackets can force the flexible element sideways, increasing stress and reducing service life.

Are Air Bellows Used in Doctor Blade Systems?

Pneumatic force is widely used in doctor blade systems, but it is important to distinguish between a conventional convolution-style air bellow and a rubber pneumatic air tube.

A paper-machine doctor blade needs controlled contact pressure against a roll or cylinder. Too little pressure produces poor cleaning, while excessive pressure increases blade wear, roll wear, heat, and drive load.

Many doctor holders therefore use flexible rubber air tubes that run along the holder width. When the tube is pressurized, it moves the blade holder and applies relatively uniform blade pressure across the roll.

Sun Hong's Doctor Blade System includes doctor blades, holders, and pneumatic rubber air tubes for cleaning, coating, and creping applications.

Although both an air bellow and an air tube use compressed air and flexible reinforced rubber, they should not automatically be treated as the same replacement component. A guider may use a bellow actuator to create movement, while a doctor holder typically uses a long pneumatic tube to distribute force along the blade.

When ordering pneumatic parts, the exact application should therefore be specified rather than requesting only an “air bag.”

Air Bellows for Vibration Isolation and Flexible Support

Paper machines contain large rotating rolls, fabrics moving at high speed, vacuum equipment, pumps, and other sources of vibration. In selected mechanical installations, an air bellow can provide flexible support and help isolate vibration between connected structures.

The compressed-air chamber acts as a compliant element. Compared with a rigid mechanical connection, it can absorb part of the dynamic movement and reduce direct transmission of shock or vibration.

However, air bellows should not be treated as a universal vibration solution. Their effectiveness depends on load, natural frequency, pressure, mounting arrangement, and the frequency of the vibration being controlled.

A support bellow that is too stiff may transmit more vibration than expected. One that is too soft may allow excessive equipment movement. The machine structure, center of gravity, and number of support points therefore need to be considered.

For paper mills, flexible pneumatic support can be useful where controlled movement and vibration isolation are both needed, but the application should be engineered rather than improvised.

Where Is an Air Bellow Not Normally Used?

Understanding where air bellows are not used is equally important.

An air bellow is not a stock-cleaning or pulp-screening component. For example, a pressure screen removes contaminants from pulp using a screen basket and rotor. An air bellow does not perform this separation and would not normally be installed inside the stock-flow screening chamber.

Similarly, a forming fabric cleaner uses high-pressure water sprays or other cleaning methods to remove fibers, fillers, pitch, and deposits from the forming fabric. The air bellow does not clean the fabric; it helps guide or tension it.

These systems work together indirectly:

Pressure Screen → Cleaner Pulp

Forming Fabric Cleaner → Cleaner Fabric

Air Bellow Guider → Correct Fabric Position

Tensioning System → Stable Fabric Tension

Each component addresses a different cause of paper-machine instability.

This distinction is useful during troubleshooting. If the forming fabric is dirty and drainage is falling, replacing an air bellow will not solve the contamination problem. If the fabric is clean but consistently running toward one side, the guiding sensor, pneumatic bellow, guide roll, alignment, and tension system should be investigated.

How Does an Air Bellow Work With a Fabric Guider Sensor?

Automatic guiding requires both detection and actuation.

The sensor monitors the edge or position of the moving fabric. When the fabric shifts from its normal path, the sensing mechanism changes the pneumatic control signal. This creates a pressure difference in the actuator system, causing the guide roll to move.

As the guide roll angle changes, the running fabric gradually moves back toward the desired position. When the correct position is restored, the pneumatic control returns toward equilibrium.

The basic control loop is:

Fabric Deviation → Sensor Detection → Pneumatic Signal → Air Bellow Movement → Guide Roll Adjustment → Fabric Returns to Center

The response should be neither too slow nor too aggressive.

If response is too slow, the fabric may travel too far before correction occurs. If response is too aggressive, the system can overcorrect and create repeated side-to-side movement.

Air pressure, valve sensitivity, guider geometry, and sensor position should therefore be adjusted together.

What Happens When an Air Bellow Fails?

Air bellow problems usually appear as changes in machine movement rather than immediate complete failure.

A leaking bellow may require increasingly frequent air supply to maintain position. A cracked or fatigued bellow can lose force. Internal reinforcement damage may cause uneven expansion, while a restricted air line can make the actuator respond slowly.

Common symptoms include:

The complete guiding system should be checked before replacing the bellow. A new pneumatic actuator will not solve a seized guide-roll pivot or incorrectly positioned sensor.

How Does Air Bellow Condition Affect Paper Machine Clothing Life?

Poor guiding or tension control can shorten the service life of forming fabrics, press felts, and dryer fabrics.

When clothing runs against machine frames or guide devices, edge abrasion develops quickly. Repeated lateral correction can also create unnecessary stress if the guider is unstable. Excessive tension increases mechanical loading, while insufficient tension encourages wrinkles, slipping, and poor tracking.

Stable pneumatic control helps maintain a more consistent operating position. This reduces avoidable mechanical damage and allows the clothing to run under the conditions for which it was designed.

However, fabric life is also influenced by:

• Roll alignment

• Fabric quality

• Machine speed

• Cleaning

• Chemical contamination

• Abrasive fillers

• Shower condition

• Vacuum elements

• Tension level

• Installation

An air bellow should therefore be considered one part of the overall clothing management system.

Air Bellow vs Pneumatic Cylinder in Papermaking

Both devices use compressed air, but their mechanical characteristics differ.

A pneumatic cylinder uses a piston moving inside a rigid barrel. It provides a defined linear stroke and can tolerate applications requiring accurate rod movement.

An air bellow uses a flexible reinforced rubber body without the same sliding piston arrangement. This can provide low-friction movement and greater compliance, while also helping isolate vibration.

The correct actuator depends on the mechanism. A bellow should not automatically replace a cylinder simply because both use compressed air.

How to Select an Air Bellow for Different Paper Machine Positions

The first step is identifying exactly where the component will be installed.

For a forming fabric guider, response speed, compact dimensions, and controlled corrective movement are important. A press felt guider needs similar responsiveness but may operate in a wetter and mechanically demanding environment. Dryer-section applications need additional attention to temperature. Tensioners usually require greater travel and stable force, while press or calender applications can require higher load capacity.

Selection data should include:

If replacing an existing unit, the old bellow model or accurate drawing should be supplied where possible.

How Should an Air Bellow Be Installed?

Installation strongly affects service life.

The top and bottom mounting surfaces should be aligned so the bellow compresses primarily along its intended axis. Excessive offset or angular misalignment can create side loading and irregular folding.

The bellow should also remain within its permitted height range throughout machine movement. Mechanical stops may be useful in applications where the mechanism could otherwise overextend or overcompress the rubber element.

Air connections should be clean and securely sealed. Contamination entering pneumatic lines can affect valves and control response. Hoses should also be routed away from moving machine parts and hot surfaces.

After installation, operate the mechanism gradually at low pressure and confirm:

• Correct movement direction

• No abnormal rubbing

• Stable guide-roll movement

• No air leakage

• Correct minimum and maximum position

• Proper sensor response

• Stable pressure

Full-speed paper-machine operation should only begin after the guider or tensioner has been checked throughout its working range.

How Should Air Bellows Be Maintained?

Air bellows normally require less mechanical lubrication than rigid sliding actuators, but they still need routine inspection.

Maintenance teams should look for cracks, bulging, delamination, abrasion, oil contamination, loose fittings, corrosion, and air leakage. The pneumatic system should also be checked because poor air quality or unstable pressure can create actuator problems even when the rubber component itself is healthy.

Important maintenance items include:

• Air regulator condition

• Pressure gauge accuracy

• Filters and water separators

• Pneumatic control valves

• Air hoses

• Fittings

• Sensor position

• Bellow surface condition

• Mounting bolts

• Guide-roll movement

During planned shutdowns, the mechanism should be moved through its full operating range to confirm that it does not bind mechanically.

Preventive inspection is preferable to waiting for complete bellow failure because clothing-guiding problems can quickly damage expensive forming fabrics or press felts.

How Do Air Bellows Fit Into the Complete Paper Machine System?

An air bellow performs a relatively small mechanical function, but it works inside a much larger process.

Stock preparation begins upstream, where pulpers, cleaners, refiners, and the pressure screen prepare the pulp. Cleaner stock enters the paper machine through the headbox and reaches the forming section. The forming fabric supports the fibers and removes water while guiding and tensioning systems maintain clothing stability.

A forming fabric cleaner removes deposits from the moving fabric. Air bellows and pneumatic guide systems maintain position. Press felts continue dewatering in the press section, while additional guiders and tensioners stabilize their running path. Dryer fabrics then carry the sheet through the heated dryer section and also require controlled tracking and tension.

This creates a connected maintenance chain:

Stock Preparation → Pressure Screening → Forming → Clothing Cleaning → Guiding & Tensioning → Pressing → Drying

Failure in one area can create problems elsewhere. Dirty pulp increases clothing contamination. Poor fabric cleaning reduces drainage. Incorrect guiding damages fabric edges. Unstable tension increases wrinkles and wear.

The air bellow is therefore not a major process machine, but it can have a meaningful influence on paper-machine reliability because it supports the stable movement of high-value machine clothing.

Why Choose Sun Hong Group?

Sun Hong Group was established in 2010 in Xuzhou, Jiangsu Province and initially focused on forming fabrics, press felts, and dryer fabrics. Its product scope later expanded into paper-machine spare parts, stock-preparation equipment, screen baskets, dewatering elements, spray nozzles, doctor blades, rotary joints, rolls, cleaner components, and related paper-industry equipment.

This background is relevant to air bellow selection because pneumatic guiding cannot be evaluated independently from paper machine clothing. The bellow, sensor, guide roll, forming fabric, press felt, dryer fabric, tensioner, and cleaning system all interact mechanically during paper-machine operation.

Sun Hong can supply air bellows together with pneumatic guiders and other paper-machine spare parts. For replacement applications, customers can provide the existing bellow dimensions, photos, drawings, machine position, and operating pressure. For new guiding or tensioning projects, machine width, clothing speed, required stroke, load, installation space, and environmental conditions can be used to develop a suitable configuration.

The company's broader paper-machine product range also allows technical discussions to consider the surrounding machine system rather than treating the air bellow as an isolated rubber component.

Conclusion

Air bellows are used mainly where paper machines need flexible pneumatic movement, controlled force, automatic correction, tension adjustment, or vibration isolation.

Their most common applications include forming fabric guiding, press felt guiding, dryer fabric guiding, felt and fabric tensioning, guide-roll positioning, and selected press or calender support systems. Related pneumatic rubber air tubes are also used in doctor blade holders, although these should be distinguished from conventional convolution-style bellows.

The most important application is often paper machine clothing control. Forming fabrics, press felts, and dryer fabrics must remain centered and correctly tensioned while running over long roll paths at high speed. A pneumatic bellow guider allows small automatic roll adjustments that return the clothing toward its correct running position.

Air bellows do not replace a pressure screen or forming fabric cleaner. The pressure screen improves pulp cleanliness, the cleaner removes deposits from clothing, while the air bellow controls mechanical position. Together with tensioners, rolls, sensors, and other components, these systems contribute to stable paper-machine operation.

For accurate air bellow selection, provide Sun Hong Group with the machine section, application, installed height, required stroke, working pressure, maximum pressure, load, temperature, mounting dimensions, paper-machine width, and clothing speed. This information makes it easier to select a pneumatic component suited to the actual papermaking position rather than simply matching the outside dimensions of an existing bellow.

FAQ

Where is an air bellow used in a paper machine?

Air bellows are commonly used in forming fabric, press felt, and dryer fabric guiding systems, fabric tensioners, guide-roll positioning mechanisms, and selected press, calender, or flexible-support applications.

How does an air bellow guide a forming fabric?

A sensor detects lateral fabric movement and changes the pneumatic control signal. The air bellow actuator moves the guide roll slightly, changing its angle and steering the forming fabric back toward its normal running position.

Is an air bellow used with press felt?

Yes. Pneumatic bellow guiders can be used to correct press felt deviation. Stable felt tracking helps reduce edge wear, wrinkles, and damage caused by running against machine structures.

Can an air bellow be used with dryer fabric?

Yes, provided the bellow and pneumatic components are suitable for the dryer-section temperature and operating conditions. The system can control guide-roll movement and help maintain stable dryer fabric tracking.

What is the difference between an air bellow guider and a fabric tensioner?

A guider controls lateral clothing position by changing guide-roll alignment. A tensioner changes roll position to maintain the required forming fabric, press felt, or dryer fabric tension.

Is an air bellow used in a doctor blade holder?

Doctor blade holders commonly use pneumatic rubber air tubes to apply blade pressure. These flexible pneumatic tubes use a similar compressed-air principle but should not automatically be treated as the same component as a convolution-style air bellow.

What air pressure does a paper machine bellow guider use?

The correct pressure depends on the specific guider and load. Sun Hong's current pneumatic bellow felt and fabric guider lists a typical pneumatic pressure range of 0.2–0.5 MPa. Final settings should follow the actual mechanism requirements.

Why does a paper machine air bellow fail?

Common causes include rubber aging, excessive extension or compression, side loading, misalignment, high temperature, oil or chemical exposure, unstable air pressure, abrasion, and fatigue from repeated movement.

Can an air bellow improve paper machine clothing life?

It can contribute indirectly by maintaining more stable fabric or felt tracking and tension. Correct guiding reduces avoidable edge abrasion, wrinkles, and mechanical damage, although clothing life also depends on cleaning, alignment, tension, contamination, and operating conditions.

Is an air bellow part of a pressure screen?

Normally, no. A pressure screen uses a screen basket and rotor to remove contaminants from pulp. Air bellows are mainly pneumatic mechanical components used for guiding, tensioning, support, and adjustment elsewhere on the paper machine.

What is the role of an air bellow with a forming fabric cleaner?

The two components perform different functions. The forming fabric cleaner removes deposits from the fabric, while the air bellow guider helps keep the fabric centered. Both can contribute to stable forming-section operation.

How do I choose an air bellow for a felt guider?

Provide the machine width, felt speed, operating pressure, installed height, minimum and maximum height, required stroke, actuator load, mounting dimensions, temperature, and existing guider configuration.

What should be checked when replacing a paper machine air bellow?

Check overall dimensions, mounting pattern, working height, stroke, pressure rating, load, air-port position, surrounding temperature, chemical exposure, guide-roll movement, and sensor operation before selecting the replacement.