Raschig - Valve Trays
From Fractionation Trays
Like sieve trays, valve trays have been in use as far back as the 1950's but nowadays have become the more popular choice because of their greater operating range properties. Valve trays are essentially flat perforated trays with moveable or fixed valve units with or without a cage structure covering the holes. Moveable valves are disk-shaped type devices which are enclosed within a cage structure or contain legs formed out of the valve disk. Fixed valves are units with integral legs formed out of the tray deck.
The open or vertical curtain area of the valve, through which vapour issues in a horizontal direction is defined by the restrictive legs integral with the valve unit or the leg-rise of the cage structure attached to the tray deck. As the vapour rate is increased, the valve units rise and the upper limit of opening is controlled by the valve leg height. It is at high vapour rates that valves serve to deflect entrainment first before propagating upwards unlike sieve trays. Upon decreasing the vapour rate, the curtain area of the valves decreases or valves settle intermittently over the holes. This minimizes liquid weeping while maintaining good operation at low flow rates. It is a combination of the above that permit valve trays to perform over a wider operating range and thus a higher turndown compared with sieve trays.
The Raschig USA can offer several types of valve units depending on the hydraulic loadings and the application.
- Movable valves: RJ-V1, RJ-V4
- Caged valves: RJ-A1, RJ-A3, RJ-A4
- Fixed Valve: RJ-VO, RJ-SVG, RJ-MV