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Two-Port Diverter Valves

The purpose of this valve is to divert the flue gas flow from the CO boiler to the stack. Under normal conditions the flue gas flows directly from the inlet port to the CO boiler where the combustion from CO to CO₂ takes place, while the stack port is kept in the closed position. The flue gas is diverted to stack and thereafter into the environment whenever the CO Boiler is out of order.

REMOSA currently designs and manufactures four types of two-port diverter valves [see chart]:

• Linear
• Pendulum or Rotary
• Two-Butterfly
• Flip-Flop

For linear and pendulum type, opening and closing operations are carried out by a disc - sliding from one port to the other in the former and swinging in the latter. The operation of a linear type is rather simple when compared with the pendulum type, but the deciding factor on whether to use a linear or pendulum type is port size: linear type Two-Port Diverter valves occupy much more space than the pendulum types [drawing, below], therefore their use is usually restricted to relatively small port sizes. Using a linear type, apart from occupying more space would require guides that by reason of their length could have flatness problems.

The Two-Butterfly is a special type of Two-Port Diverter Valve where opening and closing operations are carried out by a butterfly on each port.

In all cases the body of this valve is made of SA 516 Gr 70 carbon steel provided with a refractory lining. All internal parts are made of SA 240 Tp 304 H stainless steel. Depending on specifications the disc can be flat or curved type. The disc and orifice plate rest on seat rings [photo, left] supported by two cones welded to the outlet ports and are hard-faced by cobalt-base material using a Plasma Transferred Arc process which ensures a hardness of 58-60 HRC.

In the pendulum type the disc is moved from one port to the other by means of an arm connected to a shaft. Torque to the shaft is transferred from a hydraulic actuator providing thrust to either a rack and pinion system or a lever system.

Due to the high operating temperature, the required mechanical strength of the shaft [photo, right] is achieved using INCONEL X-750 material, subjected to triple heat treatment according to AMS 5668 specification.

In the linear type Two-Port Diverter Valve the disc slides along two guides. The thrust to the disc is provided by a hydraulic actuator which is connected to the disc itself. Unlike the pendulum type, the stem in this type of valve is made of SA 182 Tp 304H.

Copyright © REMOSA spa 1998-2001 Last updated on June 28, 1999