On the selection of valves
April 2003
Valves, Actuators & Pump Control
Valve selection in the main is an arbitrary subject. It can be based on many factors such as tradition, operational experience, perceived suitability for process conditions, operational lifespan requirements, initial cost, or a combination of any of these. Due to prevailing market conditions initial cost has tended to become a major factor, particularly in plants such as those for potable water, waste or effluent treatment.
Whereas for particular applications when operational and/or sizing requirements necessitate the use of gate valves for isolation, initial cost considerations have tended towards the selection of quarter-turn valves. There are a variety of quarter-turn valves available; the most commonly used being the rubber-lined wafer butterfly valve. This valve is mainly space/mass saving, inexpensive to purchase and maintain, easy to operate and relatively inexpensive to automate. If selected correctly for the application, rubber-lined butterfly valves of good quality and design can be a good choice.
Other popular quarter-turn designs are ball valves and plug valves. The former is a cost-effective and reliable solution for clean applications and where minimal pressure drops are required, whilst the latter is usually more expensive, but provides a higher standard of shut-off and is better suited to aggressive applications.
Due care should be taken over the selection criteria to ensure that the valve of choice is fit-for-purpose rather than just cost-effective.
This is not to say that initial cost should be discounted, but rather that it should be one of several factors that influence valve selection. In this regard the valve manufacturer, or supplier, should be involved in the selection process as much as possible.
As with most types of equipment, there are varying standards of design within each valve category. A basic description or specification can encompass a wide range of valves but with differing design features, and so providing varying service life spans and degrees of maintainability.
These factors should also be taken into consideration and verified with the supplier during the valve selection process, as they may impact on the overall cost of the valve in terms of the operational life of the plant.
Quarter-turn valves are also used for fluid control purposes, and can prove to be a reliable and cost-effective alternative to traditional and (sometimes) more costly control valve designs, and providing that complete process and control application details are given to the valve supplier.
For more information contact El-o-matic, 011 974 3336.
Further reading:
Compact valve position indicator
Emerson Automation Solutions
Valves, Actuators & Pump Control
Emerson’s new TopWorx DVR Switchbox is an entry-level addition to the DV Series of valve position indicators. It combines a durable resin enclosure, compact size, and a patented cam design that provides a reliable valve position feedback for water and wastewater systems, food and beverage production lines, and industrial utilities.
Read more...
Dependable pumping for dewatering in hard rock mining areas
Valves, Actuators & Pump Control
Becker Mining’s Pumpor Vertical Spindle (PVS) pumps are hard at work on many mines throughout Africa, with many units installed recently in the Carletonville area, West of Johannesburg.
Read more...
Efficient, affordable solution for electrohydraulic pumps
Parker Hannifin - Sales Company South Africa
Valves, Actuators & Pump Control
In the world of construction a revolution is changing the status quo, the electrification of small and efficient construction machinery.
Read more...
Redefining Industrial Automation with the new Festo Valve Terminal
Festo South Africa
Valves, Actuators & Pump Control
Festo recently introduced its latest innovation in the form of the Valve Terminal VTUX. This invention marks the beginning of a new era in valve terminals, with its features making it an impressive solution for the future.
Read more...
New pilot-operated relief valve
Emerson Automation Solutions
Valves, Actuators & Pump Control
Emerson has introduced a pilot-operated relief valve for installation on pressurised bullet tanks used to store liquid propane and anhydrous ammonia. This type of pressure relief valve is typically installed on tanks fabricated by OEMs for end users, engineering firms, or contractor customers.
Read more...
Pulse valves for dust collection
Emerson Automation Solutions
Valves, Actuators & Pump Control
In process manufacturing, especially hard mineral mining, dust particles are unavoidable. If this pervasive dust is not effectively removed, it can accumulate throughout mines, plants and other facilities, becoming hazardous to workers and equipment.
Read more...
Case History 191: The weakest link.
Michael Brown Control Engineering
Valves, Actuators & Pump Control
Which is the weakest link in a control loop? The answer, without any doubt is that, in most cases, the final control element is the weakest link.
Read more...
High-flow solenoid valve
Emerson Automation Solutions
Valves, Actuators & Pump Control
Emerson has introduced the new ASCO Series 327C solenoid valve, which features a direct-acting, high-flow design that provides superior flow-to-power ratio. It permits high flows at minimum power levels, making it ideal for use in power plants, refineries, and chemical processing facilities.
Read more...
Selection of two-port valves: an open and shut case
SMC Corporation South Africa
Valves, Actuators & Pump Control
Little consideration is generally given to two-port valves because they are often perceived as simple devices that only open and close to control downstream fluid supply. Although this is mechanically true, choosing the optimal two-port valve for your application can make a big difference, saving space, weight and energy consumption.
Read more...
Emerson software optimises maintenance
Emerson Automation Solutions
Valves, Actuators & Pump Control
Emerson has announced the Plantweb Insight Valve Health Application, a powerful software tool that combines Fisher control valve expertise with advanced analytic algorithms. The new app makes it possible for users to visualise an entire connected fleet of valves, while prioritising actions based on the health index of each valve.
Read more...
printer friendly version