Flexible joints

Flexible Connectors: Vibration Isolation and Compensation

Flexible connectors (fabric expansion joints) are essential components in industrial aspiration systems, serving as a link between vibrating equipment (fans, crushers, filters) and the network of rigid ductwork. Their main purpose is to prevent the transmission of vibration and to compensate for thermal expansion or minor installation misalignments.

Main Functions of Flexible Connectors

• Vibration Isolation: Effectively dampens vibrations from fans and other machinery, reducing noise and preventing damage to welds and joints in the rigid ductwork.
• Stress Compensation: Compensates for the thermal expansion of metal ductwork when handling warm air and allows for minor inaccuracies during the installation of equipment and ducts.
• Abrasion Resistance: The fabric part of the connector must withstand the abrasive action of dust and shavings carried by the airflow.

Construction and Materials of Flexible Connectors

A flexible connector consists of two main parts:

• Rigid Frame: The base of the connector, which provides attachment to the ductwork or equipment. It is made of durable steel (galvanized or stainless) with a thickness typically ranging from 1.5 to 5 mm. For a maximally airtight and robust connection, a frame with flanges for bolted assembly is often used. Flanged connections also significantly simplify the removal of the connector for maintenance or replacement. Ensuring the airtightness of a flanged connection requires the correct selection of a gasket (NBR is standard; Viton or PTFE for special conditions) depending on the operating temperature and medium.
• Flexible Fabric Element: Made from wear-resistant and heat-resistant materials. Standard fabrics typically operate in a temperature range from -40°C to +150°C. Polyurethane (PU) fabric is often used for high abrasion resistance, or silicone fabric for higher temperatures (up to +200°C), often reinforced with fiberglass for added strength. The specific material choice depends on the operating conditions.

Safety Requirements

When an aspiration system handles combustible dust (wood, plastic, flour, etc.), there is a risk of ignition from static electricity. Friction between particles and the flexible connector material can lead to static charge build-up and spark generation.

ATEX Directive: The European directive ATEX 2014/34/EU sets strict requirements for equipment used in potentially explosive atmospheres. A key requirement for flexible elements is the prevention of static electricity accumulation. Read more about ATEX on the main page of this section.

• Antistatic Design: For operation in ATEX zones, flexible connectors must be made from special conductive (antistatic) materials that safely dissipate static charge to the grounded frame.
• Grounding: The metal frame and flanges of the connector must be reliably grounded along with the entire ductwork system.

Correct Material Selection: Choosing a flexible connector for an explosive atmosphere requires special attention. Using materials that do not possess antistatic properties and are not intended for ATEX zones is not permitted under safety regulations.

We strongly recommend consulting our specialists when selecting a flexible connector for handling combustible dust to ensure the choice of the correct material and full compliance with ATEX requirements.

Operation and Maintenance

A flexible connector is a component subject to wear, especially its fabric part. To ensure reliable system operation:

• Regularly inspect the fabric element for cracks, tears, abrasions, or other damage.
• During installation, ensure the connector is installed without twists and without excessive tension or compression of the fabric.
• Tighten flange bolts evenly in a cross pattern to ensure an airtight seal without deforming the flanges.

Ordering and Selection

We manufacture flanged flexible connectors in standard diameters. Contact our engineers to select the appropriate connector for your operating conditions, especially if an ATEX-compliant version is required.