The SPX brand Copes-Vulcan is well known for the supply of high quality control valves and desuperheaters. It has particular expertise in the power industry and developed its Direct Steam Conditioning Valve with Steam Atomising (DSCV-SA) specifically for heavy-duty applications such as steam turbine bypass. SPX has seen exceptional sales growth of this highly reliable valve over the past few years as the power industry comes to recognise the huge benefits of its design.
Vital to the safe and efficient operation of a power plant, the DSCV-SA has been designed for ultimate reliability. It uses high pressure balancing which removes the need for wear parts such as piston rings and seals found in low pressure equivalents and provides a very tight and repeatable shut-off. Without wear parts which need frequent replacement, the valve has negligible maintenance requirements and has high tolerance to debris in the system.
When in the closed position a pilot plug design means the main plug within the valve is unbalanced with full steam pressure acting on top. Combined with the actuator thrust this creates an extremely high seat contact and ensures a very tight shut off without relying on auxiliary balancing seals and close tolerance sealing surfaces. When open high-pressure steam floods the valve to the underside of the main plug, balancing it and reducing the actuation thrusts required. This design not only provides repeatable, assured shut-off but prevents leak-induced damage to the valve seat.
To avoid thermally induced stress cracking the valve uses a highly effective atomisation system which uses the high energy within the steam to atomise water. This creates very small water particles which provide a large surface area for very efficient heat transfer. Once atomised, the stream enters a converging and diverging venturi which mixes the atomised water with the steam and pre-heats it. Many mechanical spray nozzle systems are fitted to the outlet of a valve but their design makes them dependent on the velocity of the steam. This method of adding cooling water provides limited turndown as the water atomization and spray pattern degrade as the water flow rate and available pressure differential reduces. The preheated, atomised water in the DSCV-SA is introduced at the centre of the valve, which creates a natural thermal protective barrier from a surrounding 360° annulus of hot steam. The system is not dependent upon the steam velocity, provides exceptionally high turndown and ensures protection of downstream pipework and fittings.
The reduced maintenance required by the DSCV-SA means it offers a typical payback period of around 18 months for existing installations. For new installations, this innovative valve design has eliminated use of easily damaged parts which further reduces the need for commissioning spares. Its increasing popularity is a reflection upon its highly repeatable, reliable tight shut off created by the use of high pressure balancing and the downstream protection it affords from its efficient steam atomisation system. The valve’s exceptional performance and reliability offer real opportunities to reduce on going costs and improve power station safety and efficiency.
Mary Anne Johnson
Marketing Controller, SPX Flow Technology
Maryanne.Johnson@spx.com
Tel +44 (0) 1604 889921
www.spx.com
