General Features of the Standard PT&M Screw Press

screw-press-elevatedPress Technology & Manufacturing, Inc. (PT&M) is a manufacturer of durable screw presses used for liquid/solid separation with applications in the pulp & paper industry, municipal waste treatment and other industries. These industries require equipment that is durable and easily maintained. Appropriately lubricated Press Technology screw presses will operate continuously for 3 to 5 years between maintenance repairs and have useful life of over 20 years. Press Technology manufactures screw presses in a variety of makes and models with screw diameters from 4 inches through 48 inches.

The standard material used in the construction of a PT&M Screw Press is 304 Stainless Steel on wetted surfaces with a carbon steel base. When requested, other grades such as 316 Stainless Steel are available on all surfaces of the press. PT&M Screw Presses are built with a 9:1 ratio of screen area length to diameter of screw. This gives the PT&M Screw Press an advantage over the competing screw presses in its hydraulic capacity. PT&M Screw Presses are sized by their hydraulic and mechanical capacity; the hydraulic capacity is the limiting factor determining size.

Screw Shaft

The screw shaft body is tapered and the flight pitch is decreased to create a gradual volume reduction. Stainless Steel is on all wetted surfaces. The discharge flights are hardfaced with Stoody VanCar 0 hardface. PT&M manufactures its large sludge presses with center shaft drainage at the discharge end of the screw. Large sludge presses have a thick discharge cake that does not provide for uniform dryness. The center shaft drainage reduces by half the path moisture needs to travel. The additional dryness obtained with center shaft drainage will improve the energy value of the sludge when it is used as fuel or reduce landfill cost.

Screen Cage Assemblies

Split screen assemblies located between the inlet housing and the discharge housings can be unbolted in two halves and can be replaced without removing the shaft or other screen sections. The screen sections are built up to 48″ in length with backing ribs that are spaced to give the screen support and strength. In pressure zone the screen sections come with heavy backing screen plates in a range of thicknesses between 1/4″ through 1/2″ with 3/4-inch perforated holes. The inner screen is 11-gauge plate with hole sizes ranging from 1mm conical drilled holes to 1/8-inch perforated. The inner screen can be replaced on all screen sections.

Filtrate Pan

Stainless Steel construction is integrated within the framework from inlet to discharge housing on a 1/4″ per ft. slope to a maximum depth at the center of the drain flange.

Backpressure Cone Assembly

Two air cylinders drive the back pressure cone to control the discharge dryness. The air pressure is controlled manually or automatically and is operated from a bi-directional air regulator from 0 to 125 psi. The regulator will regulate the air pressure at the set value in both directions; thus the pressure on the cone is constant regardless of the cone position. The cone is split and can be unbolted and the bushing material can be replaced without removing the shaft.

The pneumatically regulated cone gives the PT&M Screw Press a big advantage over screw presses with fixed or spring loaded cones. The PT&M Screw Press can handle changes in feed consistencies without affecting the discharge dryness.

Base Frame

Material of construction is carbon steel. Welded one piece heavy duty channel with integral cross bars and plate decking, all primed with one coat industrial primer and painted in 2 coats of Industrial Blue Print Blue.

Screen Covers

Lift-off screen covers are 16-gauge SS with a #3 finish. The size and weight of each panel is such that a single cover can be easily removed by an individual using the two stainless steel handles.


The thrust bearing and wet end seals are mounted externally and can be inspected or replaced by removing only eight bolts. The seals are the V-Ring type and cannot wear or groove the shaft because the seal will rotate with the shaft. The wear surfaces are a waterjet cut 1/4-inch plate. The seal wear plates are also replaceable without removing the screw shaft. The wet end thrust bearing is protected by three seals and a liquid drain.

Inlet-end Thrust Bearing

Inlet end spherical roller thrust bearing has a B10 Life of 100,000 hrs. Lubrication frequency is once per week. The thrust bearing can easily be replaced without removing the screw shaft or gear reducer.