EXTRU - The reliable extrusion gear pump
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 gentler manner. The EXTRU 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 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.
Technical Features
Housing
Heat resistant carbon steel, e.g. 1.6582 · rust-free stainless steel 1.4313 · with optional coating
Gears
Tool steel · nitrated steel · special steel · with optional surface
coating · helical gearing · herringbone gearing (for extremely
low-pulsation conveyance)
Friction Bearings
Tool steel · NiAg (nickel-silver) · Al-bronze · special materials · with optional surface coating
Shaft Seal
Viscoseal · stuffing box
Electrically, by means of heating cartridges · optional cover heating
Operating Parameters
Viscosity
up to 40000 Pas
Temperature
up to 400°C (752°F)
Inlet pressure
Up to max. 120 bar (1740 psig)
Differential Pressure
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.
Pump Sizes
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).
Application Examples
Polymers
PS · PET · PVC · PC · PA · PMMA · HDPE · LDPE · LLDPE · PP · Polysulphones · PEEK
Food industry
Liquorice · chewing gum
Viscoseal (VS)
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)
Stuffing Box
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)