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Intertronics’ preeflow eco-DUO adhesive dispensing system is helping to ensure the integrity of a life-saving medical device.

The latest product from Intertronics customer BPR Medical is the Bidirectional Firesafe Cannula Valve. The valve is designed for use in home medical oxygen supplies to extinguish fires occurring in the line between the concentrator and the user’s mask or nasal cannula. Such fires can occur if the line comes into contact with an ambient flame, such as a candle, or more commonly if the patient is a smoker. The UK’s Home Oxygen Service supports around 90,000 patients.

BPR’s inline Bidirectional Firesafe Cannula Valve extinguishes the fire by cutting off the oxygen supply. It is a development of an existing, unidirectional design and acts as a thermal fuse whereby the oxygen supply is cut off when a fusible component softens as a result of the heat from an approaching fire in the oxygen delivery tube.

Having chosen a two-part epoxy to bond both halves of the valve’s body, BPR had to find a dispensing solution that would assure deposition of a precise, repeatable volume of the adhesive, metered and mixed in the correct ratio, on to a cylindrical assembly. The resulting bond integrity had to conform to the European Medical Device Directive.

BPR Medical technical director Ben Johnson’s team evaluated several options, including pre-mixing and dispensing via a pinch-tube valve. This yielded inconsistent results due to changes in viscosity, which  occur naturally as soon as epoxy is mixed, exacerbated by temperature fluctuations. It also took an unacceptable amount of set-up and clean-up time.

Having determined that volumetric technology would provide a better solution, BPR contacted Intertronics and two other vendors to arrange equipment demonstrations. Trials using the selected epoxy were conducted in a wide ambient temperature range, and rigorous pull, flexural and other testing of the assembled valve revealed that the preeflow eco-DUO precision metering, mixing and dispensing system from Intertronics was the best solution.

The system offers ±1 per cent dosing accuracy and >99 per cent repeatability. It can dispense volume flows of 0.2-32ml per minute, with a minimum volume of 0.01ml. The preeflow positive displacement technology means that the volume dispensed is not affected by viscosity changes in the material.

Intertronics was selected not only because the eco-DUO met BPR’s needs but also for the lower total cost of ownership and the promise of initial and ongoing support.

Johnson and BPR product development programme manager Mike Brudenell worked with Intertronics to configure the dispenser into its bespoke manufacturing jig, into which the two populated halves of the valve body are manually loaded prior to being rotated while the epoxy is applied.

Each of the 20,000 units per month produced at the time of writing is non-destructively tested, while regular samples are subject to a three-point flexural test.

The system operates an automatic purge at the end of the shift, eliminating the need for cleaning down. Control is via a preeflow plug ’n’ mix interface and stored settings ensure consistency and repeatability, while eliminating daily set-up time. Thanks to preeflow’s accuracy, the volume of epoxy applied has been reduced to 0.05g from the pinch-tube valve’s 0.06g.

Johnson said: “We had to go through a number of stringent processes to ensure the integrity of the bonding of the two body halves. An essential part of this was how the two-part epoxy adhesive was applied, to ensure a highly accurate, repeatable dose on a rotating jig but also to maintain the correct dispense volume regardless of viscosity changes caused by temperature.

“Intertronics helped us choose a volumetric dispensing solution that was the best one for our needs. We estimate our return on investment to be in the region of £2,000 a month.”

BPR Medical is a small British company based in Mansfield, Nottingham.


INTERTRONICS supplies a comprehensive range of bonding and protective materials – together with the associated consumables and equipment – to customers in high technology, high performance assembly industries – including electronics, medical device, plastics, optical, automotive, energy, defence and aerospace.

INTERTRONICS supplies adhesives, coatings, sealants and equipment to customers with high technology, high performance assembly applications. Our customers are manufacturers in industries such as electronics, medical devices, plastics, optical, automotive, energy, defence and aerospace.

We specialise in adhesives and adhesive systems, namely bonding, coating, sealing, encapsulating, potting, masking and gasketing products, together with the most appropriate equipment and accessories for surface preparation, mixing, application, dispensing, and curing them. The provision of insightful technical and applications guidance is a cornerstone of our business. We help you find the optimal materials and processes for the manufacture, assembly or repair of your products, safeguarding and enhancing performance and integrity and, in turn, your profitability and reputation.

Ever since being established in 1979, when our main market was the printed circuit board assembly industry, we have enjoyed a reputation for customer focus, excellent service and post-sales support. We now supply over 3,000 regular customers, including multinational manufacturers, production facilities, specialist design and development businesses, universities, training organisations and government establishments.

Our Technology Centre, located in Oxfordshire with excellent road and rail links, is custom-designed for hands-on demonstrations and trials, hosted by our product specialists.

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