Design of a Vacuum Drum Filter

The main components of a chum filter are the filter drum, the filter trough, the control valve, the agitator and the device for discharge of the filter cake. 

The Filter Drum The filter drum is an enclosed cylinder lying horizontally, suspended to rotate around its centre axis. The interior is reinforced by means of intermediate rings. The filtration area on the drum surface is divided into independent cells by division strips having a swallowtail-shaped groove. At the head ends of the drum there are also grooved strips applied. 

The drum deck is formed by replaceable filter grids (sieve-plates), which support the filter cloth required for retention of the solids. The filter cloth (usually fabric or metal) is placed into the division strip grooves and fixed by means of a rubber caulk or similar. The supporting filter grids are honeycomb in form, whereby the largest possible cross-section and high filtration capacities are achieved. In the propylene version, as a result of the non-sticky properties of this material, encrustation is virtually excluded. At one end of the drum, there are radial outlet coimections for each cell for the filtrate draw off. These are readily accessible, and do not project beyond the level of the drum deck. For leading the filtrate away, the connections are joined to filtrate pipes by means of sleeves. 

The filter cloth required for retention of the solids is fixed into the grooves by means of rubber strings or similar. 

The Control Valve The other end ofthe filtrate pipe discharges after a 90 bend into the control valve faceplate, arranged parallel to the face of the drum. The so-called control plate is fixed to the control valve and forms the counterpiece to the faceplate. Various filtrate pipe sections are connected through apertures in the control plate. These apertures control the filter cycle inasmuch as, according to its position, the cell is evacuated by the vacuum connection, blocked or blown out with 

---

Figure 18.6 is a schematic illustration of the design of a vacuum drum filter with external filtrate pipework. 

---