Material world
28 May 2014
The types of materials selected for valves are critical to their performance, as is the design of the pumping system within which they are included. Bryan Orchard reports.
Advances in technology have driven significant change in the pumps and valves industry. Composite materials now represent a major opportunity for the industrial market, while developments in control technology have become ever more complex.
“Choosing the correct design and specification for a process valve can save costs, reduce downtime and minimise product loss or contamination,” says Dixon Group Europe hygienic product manager Ike Topselvi.
It is a familiar theme that will resonate with both valve and pump manufacturers and their customers.
Whereas materials have to match the demands of the nature of the fluid being handled, the correct mounting conditions of an actuator and the type of actuator selected are equally as important to operating efficiency and reliability.
“Traditional valve construction materials – iron, stainless steels and metal alloys - whilst still providing a robust choice for the end user, no longer represent the preferred choice for many applications,” says Roger Affolter, Pentair Valves & Controls global product manager for resilient seated butterfly valves.
“Advances in polymer technology have produced a range of thermosetting polymers and thermoplastics with robust mechanical properties, allowing them to be engineered as alternative components. Using composite materials for components impacts on design, performance, cost and sustainability characteristics, all being issues that influence the specification of flow control valves.”
Composite materials have made huge progress in recent years. Their improved mechanical properties, as well as their chemical and physical behaviour, now deliver comparable performance to traditional metal resilient seated butterfly valves, demonstrating significant benefits for the industry.
“New materials call for new ideas,” says Affolter.
“The adaptability of composite materials shape every element of design and it is now possible to eliminate material where it is not needed, to create hollow sections within the valve body. Whilst some plastic valve designs already employ hollow sections, these are on the exterior of the valve body which can allow dirt and dust to collect.”
For example, with quarter-turn industrial butterfly valves the improved mechanical properties of composites and their chemical and physical properties ensure that they can deliver performance that is comparable to - or better than – a metal resilient seated valve and additionally offer reduced weight and better corrosion resistance.
Pentair Valves & Controls development programmes have focused on seat and disc stem design for better service and fast installation.
By using an innovative design in combination with existing moulding technologies, the one piece disc stem has a thin profile resulting in a high Kv/Cv values.
Furthermore, incorporating a double D shaft design gives a clear visual indication of disc position even when the valve is installed in the pipe line, and four multi-drilled locating holes compatible with PN 6/10/16 and ANSI 150 guarantee perfect concentric positioning between pipe flanges.
Research by Pentair Valves & Controls and its partners has led to a blend of two thermoplastics which offer exceptional design flexibility and an opportunity to improve both shaft and disc design.
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