Screw Press Description
The Vincent horizontal continuous press is a dewatering machine with a conveying screw rotating inside a perforated cylinder. Incoming material is forced the length of the machine, liquid "press liquor") is expelled through the cylinder wall. The remaining solids ("press cake") are discharged at the far end.
The press is available in sizes with screws ranging from 4" to 30" in diameter. The screw has a graduated pitch, interrupted flight design. This screw interacts with stationary resistor teeth. These teeth assure that the material to be pressed (1) does not turn (co-rotate) with the screw and (2) is intermixed during passage through the press. Because of this, more material is exposed to the screening surface.
The graduated pitch screw gradually compresses the material as it passes through the main screen cylinder of the press. The press liquor is forced through the perforations in the screen.
The press cake encounters resistance at the discharge of the cylinder in the form of a cone mounted on a ram. As the material reaches the discharge point, the cone exerts final pressing action to achieve maximum dewatering. The cone system allows easy adjustment of the resistance to cake discharge.
This cone assembly may incorporate a unique discharge pinch point, described in a patent as a frustum, the converging angle formed by the cone face and main screen section. The change in direction as the press cake enters this area assures fresh material contact with screen surface. This converging pinch area has proven to give excellent final pressing action.
Air cylinders, springs, or counterweights actuate the cone assembly, depending on the model. It is available in both rotating and non-rotating versions. The standard, non-rotating cone is used for pulpy, fibrous and less slippery materials, while the revolving cone model is required to permit pressing of slippery, low fiber content materials that tend to "channel" in a standard screw press.
The design features of the Vincent Series VP Presses give greater screen areas than found in conventional presses. The hopper section has a screen area covering 180º of the periphery of the screw to allow drainage of free water. The main screen section has a full 360° screen area, approximately four screw diameters in length. The cone assembly also has a screen area with a separate drain pan.
The standard drive arrangement for the Vincent Press is a gear reducer directly coupled to the screw shaft. Variable speed drive arrangements, although rarely used, are available to allow maximizing capacity as feed characteristics change. This type of drive is recommended either when different products are to be processed or when major seasonal variations occur.
The press is fed from the top at the drive end through a rectangular flanged hopper. The press cake discharges at the far end, between the bedframe beams below the cone section. Press liquor drainage is through standard or sanitary pipe connections; these are attached to the pan under the screen section.
CAPACITY: The rated capacity of the Vincent Continuous Screw Press is proportional to the bulk density of the material to be pressed, as well as the slippage characteristic of the material. The ability of the material to give up its moisture, its particle size, and its fibrous content are factors to be considered. The high capacity of this machine, its low head room requirement, as well as low horsepower factor, are some of its many advantages.
The capacity and the water removed during pressing can be varied by adjusting the cone pressure. Adjusting this pressure assures maximum dewatering over a wide range of feed rates, permitting good turndown from rated capacity.
SCREENS:The screen frames can be readily opened or removed for ease of cleaning and screen maintenance. The screens of the Vincent Press are available in a variety of arrangements and screen perforation sizes, commonly in the 0.023" to 0.095" diameter range. With wedge wire screens, 0.012" to 0.030" slots are commonly used. Selection is determined by the material being pressed and the desired pressing results.
MAINTENANCE: The Vincent press has been recognized for the exceptionally low maintenance costs associated with it. Easy access to all component parts keeps maintenance time to a minimum. Use of off-the-shelf components (gearbox, bearings, air cylinder, etc.) reduces maintenance costs and assures trouble-free operation. The all-fabricated design facilitates in-plant repairs should they become necessary.
MATERIALS OF CONSTRUCTION: All press models are of fabricated steel design. They are available in all stainless construction, partial stainless, and carbon steel, as follows:
H style presses are carbon steel construction, except for the perforated screening, covers, and drain pans, which are made of Type 304 stainless steel.
P style construction has (in addition to stainless steel covers, drain pans and perforated screening) a Type 304 stainless steel screw-spindle assembly.
K style construction has all contact parts, i.e. screw-spindle assembly, resistor-stop bars, screen frames, hopper and cone sections, of Type 304 stainless steel.
Special construction of Type 316 stainless steel is available. The bedframe is of carbon steel.
SERIES: There are four Series of Vincent presses available: the TSP, VP, CP, and KP.
The newest Vincent Press is the TSP Series. These have two overlapping screws. This design offers positive feeding of even very slippery materials. The best dewatering performance over the widest operating range is available in this press. The capacity and performance of the press is sensitive to changes in screw rpm, so the use of a VFD is recommended.
The traditional Vincent Press is the VP. These are differentiated by having screens in the inlet hoppers; a flared section in the main screen just ahead of the discharge cone; a single air cylinder cone actuator; and (usually) a belt drive between the motor and gearbox.
The Series CP (Compact Press) features a hollow shaft gearbox and a simplified cone drive, both of which shorten the frame of the machine. There is no screen in the inlet hopper, and profile bars screens are almost always used. These presses are available only in stainless steel construction.
The Series KP presses are designed for a "soft" squeeze. They dewater high throughputs of easily dewatered materials. Instead of a discharge cone, they use a lever actuated stopper plate. Perforated screens are used in almost all cases. Only stainless steel construction is available.
TEST FACILITIES: To conduct tests Vincent Corporation maintains laboratory and pilot equipment. Feed rates, moisture contents, percent solids, effluent characteristics, and horsepower requirements can be determined from test data.
A large fleet of rental machines are available for in-plant trials.