Syrjäytyspumppu, menetelmä sen toiminnan parantamiseksi ja kyseisen syrjäytyspumpun käyttö

A displacement pump (11) for a relatively high pressure performance environment includes a casing with first (14) and second (16) ends, with rotors (18,20) driven in the casing to effect pumping. Flushing fluid (such as sealing water or substantially fiber-free foam) is introduced into a clearance (30) between the rotors and the interior surface of the second end (16) of the casing to keep the clearance substantially free of undesirable particles or fibers, typically fibers (such as glass fibers) having greater abrasiveness than cellulose fibers, or fibers (such as synthetic fibers, or synthetic material coating cellulose fibers) having poorer heat resistance than cellulose fibers. The flushing fluid may be introduced into the clearance in a number of different ways as long the clearance is kept substantially free of the undesirable particles or fibers. The flushing fluid is introduced, preferably through a check valve, at a pressure at least slightly higher than the output pressure of the pump.