Making the right choice

Published:  07 January, 2008

PWE looks at advances in plastic valve technology and the importance of specifying the right products.

Valves are integral to any pipework system. But surprisingly they are often specified separately, which can mean the valve is not the most compatible solution for the pipework system. This can lead to potential problems, costly maintenance and repair work.

James Roper, industrial brand manager for Durapipe UK told PWE that a manual PVC-U ball valve was the only option available to specifiers and contractors 30 years ago, "but with the vast array of options on the market today it is critical that specifiers and plant managers select the right valve for the right application”.

When specifying valves, it is important to consider what they will be used for and what materials will be passing through them. This is particularly important if chemicals are involved, as it is crucial to ensure the chemical won't corrode the pipework system. It is equally important that the chosen valve type is used for the correct application as people often specify a valve that is too complex and inappropriate.

The most frequently used valve in industrial installations is the manual ball valve which is used for standard isolations to enable them to shut down sections of a plant for maintenance. While the ball valve is the most effective product for pure isolation requirements, the last two decades have seen manufacturers introduce butterfly and diaphragm valves into their ranges to cater for more complex processes. For example when valves are required to control flow or used within chemical dosing or batch control applications, either a butterfly or diaphragm valve may be more suitable because they feature variable settings to control the amount that the valve is opened.

Roper explained: “More involved processes such as controlling the flow rate of the material passing through the valve are often automated and so require an actuation device to operate the valve remotely.” Another example of the benefit of actuated valves would be if an element of the pipework system fails and it needs to be shut down, it can be done quickly and efficiently if it can be controlled remotely.

Fail safe actuators

Roper also highlighted that the benefits of fail safe actuators are not commonly used due to the initial cost outlay: “They could prove invaluable if there is a power failure which would lead to a potential flood or contamination of a system. This is particularly dangerous in chemical process applications which rely on the efficient release of an exact level of chemical into the system at regular intervals.”

He added that if there is a power failure and the chemical is not dispatched or too much is released, it could damage or contaminate the system, leading to costly repairs: “Fail safe actuators ensure that as soon as there is a loss of power, the system will automatically shut down, preventing any major damage to the plant.” This is another example of how time and money can be saved if the correct flow control products are specified at the outset.

In addition to the different types of valves, the choice of material they are made from has also been extended beyond PVC-U, to be compatible with a wider variety of pipework materials - ensuring that there are products available that can safely transport any media. PVC-U, ABS and Polypropylene are the most widely used materials in the industrial sector and all offer exceptional properties:

• PVC-U offers high chemical resistance to most acids and alkalis, aliphatic hydrocarbons and saline solutions, making it a suitable material for transporting food grade fluids, treated and untreated drinking water and demineralised water.
• ABS is a robust and reliable material, which offers exceptional performance properties even at low temperatures including toughness, high impact strength and zero toxicity, making it equally suitable for the transportation of slurries and for the conveyance of ultrapure water. 
• Polypropylene is specifically designed to convey aggressive acids and alkalis at high temperatures. Its excellent chemical and abrasion resistance properties make it ideal for a range of industrial applications, but particularly chemical and pharmaceutical processing.

These developments offer further flexibility to the industry. As existing products continue to be developed and new products are introduced to cater for the ever-changing needs of the market, it is important that specifiers and plant managers understand what the valve will be used for and always seek advice if they are unsure of the best solution. It is the responsibility of manufacturers not only to continue to develop products to meet customers" needs but also to guide them on the most appropriate products for each specific project.

For more information please visit: www.durapipe.co.uk