Allweiler Triple Screw – SPF Series (Now Obsolete replaced by AFI Series)

General

Self-priming three-screw type of pump with internal bearing. The hardened and ground screws run in an exchangeable casing insert. The driving screw is hydraulically balanced. The axial thrust of the working screws is absorbed by the endside pump cover. Their drive is hydraulic. The thread flanks merely transmit the torque resulting from the liquid friction. Thus, the thread flanks are practically stress-free and not subject to any wear. All sliding parts are lubricated by the delivery medium being within the range of full liquid friction. The radial and axial bearing of the driving screw with pump size 10 and 20 is by the balancing piston guided in the bearing ring, with pump size 40 by a groove ball bearing. A maintenance-free mechanical seal is provided as the shaft sealing.

Sealing chamber and suction chamber are interconnected by way of a return gallery. Thus, independently of the delivery pres-sure at the shaft sealing, only the suction pressure becomes effective.  Complete units  being supplied, the connection pump/driving motor is by a pump bracket with mounting foot.

Operation

Owing to a special profiling of the thread flanks, the three screws from sealed chambers the contents of which are axially and completely continuously shifted from the suction to the pump side of the pump as the screws turn. There will be no turbulence in spite of the screw rotation. The constant chamber volume excludes squeezing. Noise/Pulsation The structural design and operation of the screw pump ensure a very low noise level and an almost pulsation-free delivery.