The rise of plastic valves
March 1st 2007

Martyn Rowlands, head of marketing for Durapipe UK discusses how plastic valve technology has evolved to offer the wide variety of options available today

The ball valve is still the most commonly used valve in industrial installations for standard isolation due to its simplicity. However, butterfly and diaphragm valves have been introduced to offer further flexibility and allow contractors to install effective systems for more complex processes. When valves are required to control flow, or are used within chemical dosing or batch control applications, these valve options are more appropriate as they have variable settings to allow the valve to be opened to the correct amount for that specific application. For more specific applications, specialist valves such as foot valves, air release valves, wafer check valves, sediment strainers and pressure release valves are also available in a variety of plastic materials, but should always be checked with the manufacturer to ensure it is being specified for the right application.

The choice of material has also extended beyond PVC-U, in line with a wider variety of pipework materials being developed to ensure there are products available that can safely transport any media. It is essential that valves keep up with the innovations in plastic pipework material to ensure pipework manufacturers are able to offer fully matched systems.

Due to the wide range of materials and various types of valves available to choose from, it is critical to select the right product. The most frequent query that the Durapipe UK technical department receives in relation to valves is customers asking which material they should use.

PVC-U, ABS and Polypropylene are the most widely used materials in the industrial sector and all offer exceptional properties, which make them ideal for a range of different industrial applications.

PVC-U guarantees excellent chemical resistance with regard to most acids and alkalis, aliphatic hydrocarbons and saline solutions. It is also the ideal material for handling food grade fluids, treated and untreated drinking water, as well as demineralised water. In addition, between 20°C and 50°C, PVC-U finds its ideal application in industrial and water supplies, guaranteeing optimal performance in terms of mechanical resistance, good rigidity, low coefficients of thermal expansion and optimal safety factors in service.

ABS is a robust and reliable material, with performance properties including toughness, high impact strength, good chemical resistance and zero toxicity. Its wide operational temperature and ability to remain ductile down to -40°C means it is equally suitable for the transportation of slurries as for the conveyance of ultra pure water.

Polypropylene is specifically designed to convey aggressive acids and alkalis at high temperatures. Its chemical and abrasion resistance properties make it ideal for a range of industrial applications, but particularly chemical and pharmaceutical processing.

In addition to the material options, the features of valves have also developed greatly over the years to enhance performance capabilities, for instance with the launch of Durapipe UK's VKD Ball Valve 12 months ago. Produced in partnership with its sister company FIP, the VKD Valve has a new, patented 'Dual Block' control, which offers anti-vibration properties. This quality prevents leaks, which can be caused when the nuts within the valve come un-locked, making it ideal for applications involving chemical or hazardous materials.

Hand in hand with the development of valve technology has been supplementary products such as flow control solutions.

Products such as controllers and indicators for measuring pH, ORP and conductivity, Industrial Epoxy and Flat Surface Self Cleaning pH and ORP Electrodes and Epoxy Body Conductivity Sensors, provide accurate and high-resolution measurement.

It is crucial that the right valve is specified for the right application.

Specifiers need to think about what the valve is required to do and what media is passing through it. The type of media will determine the valve material that is used, this is particularly important if chemicals are involved so that they don't corrode the pipework. It is equally important that the selected valve is the most effective to do the job, as Durapipe UK has found that often people try to specify a valve that is too complex for the application and a simple ball valve will be a more cost effective and appropriate solution.

Plastics have been embraced by the water and waste treatment industry for over 50 years, but Durapipe UK is looking to educate other sectors of the industrial market as to the benefits plastics can offer.

Despite the developments in the water and waste treatment industry, many other sectors still perceive plastic to be a relatively new technology and so there is a challenge to convince them of the benefits of plastics, but Durapipe UK has found that once contractors and plant managers try plastic pipework systems they become committed converters.

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