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Roadstone - Double Flap Valves 

European Gate Valves have completed a number of contracts for the supply of their double flap valves for use on Roadstone Coating Plants, due to better performance compared to rotary valves. 
Main area of application for Double Flap Valves is as a Rotary Valve replacement when they are used on the conveying system for fines/filler from the bag filter. The bag filter is situated downstream from the aggregate drier and dust loads can be quite high. 
Not all plants use pneumatic conveying systems for moving the filler from the bag filter to the storage silos. Where they are used the problems of leakage and environmental spillage can be severe. Plants have been threatened with action from the environmental agency for such discharges. 
Typical wear rates on Rotaries can result in valve change out between 2 months and a year depending on the nature of the material from the bag filter. Double Flap Valve replacement of internals vary from 3 years to about 8 years. The benefit costs can therefore be considerable. 
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Double Flap Valve with pipeloader
The Double Flap Valve is taller than the rotary for any given capacity. This can be a problem but in many cases with minor changes to chutes and discharge positions a lot can be accomplished. Some plants have the valve situated on platforms and by simply moving the conveying pipe to under the platform the height of the Double Flap Valve can be accommodated. Similarly one plant was prepared to dig a hole under the rotary to allow replacement and sweep the conveying pipe in. 
Failed rotary valves on Coating Plants
Most of the spillage has blown out of the end seals 
Drawing of Coating Plants Adjustment for Double Flap Valves
This drawing shows the kind of adjustments that can be made to install a valve. European Gate Valves went on site and accurately measured up the existing rotary valve installation and presented the above proposed installation drawing. 
Double Flap Valves can overcome most of the problems associated with rotary valves. 
The wiping action of the rotary valve inevitably wears the valve casing and increases leakage. The leakage can results in loss of operational efficiency in the process or severely damage upstream equipment. Expensive repairs to rotary valves require the complete removal of the valve from the process. 
Double Flap Valves have no wiping actions, leakage is therefore negligible and does not get appreciably worse with use and all wear components can be changed with the valve in-situ. 
Double Flap Valve installed at Coating Plant
Some plants have a complex arrangement of chutes and blowing lines due to several destinations for the filler. 
Coating Plant Installed Double Flap Valve with PLC
This FL-300 (Fabricated, Low Height, 300mm) at a London Asphalt Plant shows the typical layout where the PLC is mounted on the valve 
The double flap valves are robustly manufactured to suit a wide range of application requirements: 
Valve Bodies can be made in: Cast Iron, Cast High Nickel Chrome and Cast Aluminium 
Fabricated bodies made in Carbon steel or Stainless Steels 
High chrome alloy seats and flaps provide long life even in the most aggressive applications 
Range of Applications: 
Temperatures to 1000°C 
Differential pressures to 102 Kpa where positive is below 
Abrasiveness - Some of the most abrasive materials are comfortably handled 
Lump Size - Depends on the valve opening size 
Opening to 600mm square 
Range of actuators: 
Linear Pneumatic Cylinders 
Rotary Pneumatic Cylinders 
Electric Motor with cams or push rods 
Gravity or Manual 
Dual access covers 
Outboard Bearings 
Adjustable packed shaft seals as standard 
VDMA ISO standard cylinders 
Removable seat and flap with the valve in situ 
All metric standard components 
Wide range of optional equipment: 
PLC Control 
Flap position indication 
Heat shields 
Cooling for high temperature applications 
Purged high efficiency shaft seals 
Double Flap Valve
Double Flap Valve
Double Flap Valve
Double Flap Valve
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