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Duct clamps

Secure flexible ventilation ducting to a suitable flange or spigot with a Spiro duct clamp. Choose from 65–165, 65–325 and 65–525 mm adjustment ranges. Measure the outside diameter of the fitted duct and choose a clamp that closes securely around it. We can help you check the size and fit.

3 products

Which duct clamp fits your connection?

Choose a duct clamp, also called a hose clamp, by its adjustment range around the fitted duct. Slide the duct over the intended spigot first and measure the outside diameter where the clamp will sit. With insulated ducting, check which layer you are securing. The nominal duct diameter alone is not enough.

  • 65–165 mm: for a measured outside diameter within this range.
  • 65–325 mm: a wider range, for example when the fitted connection is larger than 165 mm.
  • 65–525 mm: the widest range in our selection, for connections within these limits.

Choose a suitable range and allow space for the band and screw fastening. The maximum size is not a fixed duct diameter. A connection measuring 170 mm across, for example, is outside the 65–165 mm range but within 65–325 mm.

Also check the diameter and fit of your duct fittings. A larger clamp cannot correct an unsuitable duct or flange size.

Spiro duct clamp with coiled metal band and screw fastening

Fastening and sealing need separate attention

Slide correctly sized flexible ducting straight over the spigot. Position the clamp over the supported part of the connection. Keep the screw accessible and tighten without deforming the duct or fitting. Switch off connected equipment before working on the joint.

The clamp holds the duct mechanically. Seal any leak paths with material suited to the duct and surface. Check for loose parts, leaks and kinks after installation. Our guide to fitting ducting, clamps and seals takes you through the full sequence.

Check the connection before ordering

Record the fitted outside diameter, duct type and space around the joint. Insulated ducting has an inner duct, insulation and an outer jacket that each need appropriate finishing. Clamping the outer jacket alone does not confirm that the inner duct is secure.

Support the duct run so weight and pulling forces do not hang from the clamp. Use a suitable duct reducer for different duct diameters or a duct connector for a straight joint. Unsure about the fit? Send us a photo and your measurements.

Advice on duct connections

All duct fitting guides

Complete your duct connection

Duct clamp questions

Need help choosing a clamp size?

Send us the measured outside diameter, duct type and a photo of the connection. We can help you choose a suitable adjustment range and connecting fittings.

  • The outside diameter of the fitted duct

  • The duct type and connection size

  • A photo of the joint and available space

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