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21st May 2019, Thornton Cleveleys

Vici offers new one-piece fitting using Victrex PAEK

Multi-use Victrex HT fitting for high-pressure range. © Vici

Multi-use Victrex HT fitting for high-pressure range. © Vici

Vici, a leading manufacturer of valves and fittings for analytical, biomedical and biocompatible precision instruments, based in Schenkon, Switzerland, is the first company to offer a new one-piece fitting using Victrex PAEK high-performance polymer.

According to Vici, the cost-effective injection moulded Victrex HT fitting can withstand the high pressures inherent in liquid chromatography systems and is, in fact, capable of withstanding pressures of up to 1,000 bar (14,500 psi), enabling more flexibility and easier handling.

The pressures required in liquid chromatography have been rising steadily for over five years, given that the particles of the separation materials (usually modified silica gels) now frequently have a grain size of two micrometres or less. Consequently, substances within mixtures can be separated more quickly, with identical efficiency.

High-quality material – high-quality fitting

To satisfy these demands, Vici has introduced a new one-piece fitting made from Victrex HT high-performance polymer, capable of withstanding pressures when tightened by hand of up to 500 bar (7,250 psi). By way of comparison, 350 bar (5,000 psi) was the limit for conventional PEEK fittings. Provided the carbon fibre reinforced Victrex HT fittings are tightened with an appropriate tool, they are suitable for significantly higher pressures of up to 1,000 bar (14,500 psi), confirmed Dr Andre Hütz, Product Manager at Vici, based upon testing the company has performed.

Such higher pressures occur between pump and column in ultra-high-performance liquid chromatography systems (UHPLC) and require that the stainless-steel connecting capillaries used for the high-pressure range are fastened with appropriate fittings. Many UHPLC applications are carried out in a pressure range of approx. 600-800 bar (8700-11,600 psi), which means that the steel capillaries used between pump and column must use this type of fittings to provide a pressure tight connection between system components.

Greater strength

The greater strength of Victrex HT polymer compared to unreinforced PEEK prevents the fitting from breaking apart when it is being tightened, since the carbon fibres are aligned in parallel by the injection process; this extra strength extends the service life of the fitting and allows several cycles of tightening and loosening of the fitting. In the past, this has only been possible in the high-pressure range using conventional two-piece ‘nut and ferrule’ fittings or complicated one-piece fittings. The design of such one-piece fittings often means they are only suitable for a specific connection and usually just for single use.

“Assisted by Victrex and its material and processing expertise, we have developed and commercialised a new product in this segment to offer users greater flexibility, reusability and above all easier handling compared to steel screw fittings. Also, being manufactured by injection moulding, it is favourable in cost terms, too,” explained Dr Hütz. “We have performed tests showing that, when tightened by hand, the new Victrex HT fittings can be used at 500 bar (7,250 psi) and above. When tightened with a tool, they can also be reused at least three times after first use at a test pressure of 950 bar (13,780 psi).”

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