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Case study: Large bespoke extension coil


We developed and produced a large fluoroplastic extension coil for a pharmaceutical application. Our customer required the coil to be custom-made and follow strict criteria, including the tubing to have a long continuous length and a small internal diameter. Given the retractable coil was so long and so thin, one of the key challenges we faced was transporting the coil safely and securely.

The project

Our customer required a bespoke extension coil for a pharmaceutical production process. The internal volume of the coil was critical and a small internal diameter for the tubing essential to ensure a high surface-to-volume ratio.

As a result, the fluoropolymer retractable coil was designed as follows:

  • Length of the tubing: 200 meters  

  • Internal diameter of the tubing: 2.4mm

  • Wall thickness of the tubing: 0.4mm

  • Length of the compressed coil: 900mm for 280 turns

  • Internal diameter of the coil: 230mm

This proved larger than most extension coils and a challenging project.

The challenges

Due to tooling restrictions, there were limits to the extension coil dimensions we could achieve, not only for the continuous length, but also the compressed length and the outside diameter of the coil. We worked closely with our customer to meet his requirements within the limitations of our tooling.

Due to the length and width of the coil, transporting such a thin and flexible tubing also proved challenging. We wanted to ensure the fluoroplastic retractable coil didn’t get damage in transport and was delivered in good condition and without tangles.

The solutions

For the extension coil material, FEP tubing was chosen. FEP is not only a stable material, but it also offers high clarity, is not prone to thermal creep, helps with heat setting and is thus ideal to form a coil. FEP also proved beneficial for the pharmaceutical application. As a result, standard-sized FDA-approved tubing was selected to be formed into a bespoke retractable coil.

In order to ensure it was not damaged in transit, the thin and flexible coil was supplied on a supportive mandrel (as pictured). This enabled the fluoropolymer extension coil to be supported while transported and delivered in good condition to the customer.

Our retractable coil services

Extension coils are not only ideal for pharmaceutical applications, but also food delivery systems. Retractable coils are extremely adaptable, offering a smooth surface and high working temperatures, and being chemically inert and acid and UV resistant.

All fluoroplastic tubing can be formed into extension coils using thermoforming technology. We can supply coils from our PTFE, FEP and PFA tubing in stock, as well as other fluropolymers. Custom sizes are also available; we can produce bespoke retractable coils in any shape or size. In addition, specialist fittings can be applied, such as flanged or flared ends.

Here at Adtech, we are specialists in delivering innovative fluoropolymer solutions for your technical applications. Find out more about our Retractable Coils.

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