The EXTRU is mainly used in conjunction with extruders or kneaders. It reduces the natural pulsation and irregular conveyance, particularly in single-screw extruders, added to which, the build up of pressure in the gear pump is more efficient in comparison to the extruder. Because of this, less energy or heat is transferred into the polymer and the product is conveyed in a gentle manner. The EXTRU melt pump is indispensable for the manufacture of precision films or micro granulate.
The robust construction and low wear materials make the EXTRU indispensable for extrusions. Special versions are available for conveying natural rubber and soft PVC. The WITTE quick colour change version lends itself particularly to master batch applications with frequent changes of colour.
In order to prevent the extrusion pump's drive shaft from being driven/pushed out of the housing when there is a high pressure on the suction side (extruder conveying pressure), the drive shaft must be relieved. It protrudes from both sides of the housing and is sealed, so that atmospheric pressure predominates on both sides of the drive shaft. The shaft is thus relieved.
Melt pump EXTRU II -
Melt pump EXTRU III -
Melt pump - quick color change version for masterbatch applications
Heat resistant carbon steel, e.g. 1.6582 · rust-free stainless steel 1.4313 · with optional coating
Tool steel · nitrated steel · special steel · with optional surface coating · helical gearing · herringbone gearing (for extremely low-pulsation conveyance)
Tool steel · NiAg (nickel-silver) · Al-bronze · special materials · with optional surface coating
Viscoseal · stuffing box
Electrically with heating cartridges · optional cover heating
up to 40000 Pas
up to 400°C (752°F)
Up to max. 120 bar (1740 psig)
Up to 250 bar (3625 psig) · special models also available for higher pressure differentials
The values listed are maximum values and must not coincide under certain circumstances.
From 22/22 (4.7 cm3/U - 10 kg/h) up to 280/280 (12000 cm3/U). Intermediate sizes, with narrower gear wheels for higher differential pressure, are possible, e.g. 140/90 (690 cm3/U).
Liquorice · chewing gum
The viscoseal is the standard seal for WITTE EXTRU and BOOSTER pumps. This is a dynamic seal for high viscosities and suction pressures. It can be provided with heating or cooling. The dynamic seal is suitable for high pressures and temperatures. Its range of use is limited by the suction pressure and the viscosity of the medium being conveyed (at least 10 Pas). The viscosity can be increased by an additional cooling system if necessary.
max. temperature: 450°C (850°F)
Viscosity: 10000 to 40000000 mPas (cP)
The stuffing box is a simple (static) seal for WITTE gear pumps. It can be provided with buffering if so desired. The range of application is similar to that of the viscoseal. The standard material used for the packing rings is made of expanded pure graphite with structural textile fibes. But it goes without saying, that other materials are also available.
max. temperature: 350°C (660 °F)
Viscosity: up to 40000000 mPas (cP)