Casing of an eccentric worm pump designed to burst at preselecte

Details Casing of an eccentric worm pump designed to burst at preselecte Casing of an eccentric worm pump designed to burst at preselecte

1993-01-22

1994-06-07

Vrablik, John J.

Rotary expansible chamber devices

Unlike helical surfaces on relatively wobbling rotating...

418153, 86 31, 102481, F04C 2107, F04C 500, F42B 3302

Patent

active

053184165

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a casing of an eccentric worm pump, comprising
a stator jacket which has at least one parting area extending throughout its length,
a stator lining of elastomeric material forming a tubular pump stator together with the stator jacket,
two casing portions, each connected by a connecting piece, with which they are formed, to a respective end of the stator jacket.
A readjustable stator for eccentric pumps is known from DE 32 18 714 C2, comprising a stator jacket made of metal or the like and an elastically deformable stator lining. The stator jacket is provided with a plurality of corrugations which are distributed around its circumference, extend in longitudinal direction of the stator, and have a radially inwardly projecting cross section with a preset breaking point. For compensation of the stator lining wear, the diameter of this known stator can be reduced by tightening a collar or clamping ring which acts on it from outside. The corrugations in the stator jacket facilitate the tightening from the very beginning and are intended to permit stronger tightening by rupturing at their preset breaking points, whereby the stator jacket is subdivided into independent jacket segments so that no further deformation work must be accomplished at the corrugations upon further tightening.
Stators of eccentric worm pumps usually are arranged between two casing portions interconnected by flanges screwed together or by tie bolts, and they each include a connecting piece extending over a respective one of the ends of the stator jacket. Such arrangements are known from DE 23 31 173 C3 and DE 25 27 141 C3 also with readjustable stators.
Eccentric worm pumps, in principle, are suited very well for conveying explosive emulsions. And yet an operating error or special circumstances may lead to pressure and temperature conditions liable to initiate an explosion within such a pump.
Such an explosion begins by an ignition process released by the supply of energy. The ignited explosive develops gases which cause the pressure to rise, thereby further accelerating the combustion speed. Modern explosives containing water--slurries or emulsions--do not burn at normal atmospheric pressure (1 bar). The minimum pressure for automatic combustion is between 5 and 20 bars, depending on the composition of a typical explosive on an hydrous base. Tests have shown that, when ignited under pressure by a short, glowing wire (point ignition), a closed container filled with an emulsion explosive does not detonate if the container is protected by a rupture disc. Such a rupture disc, however, cannot prevent detonation if the ignition takes place at many points at the same time because in that event the safety disc, with its relatively small cross section, cannot reduce the pressure build-up fast enough.
Simultaneous ignition at a number of points can occur in an eccentric worm pump if the latter is working for an extended period of time against a plugged or closed outlet. In that case the full drive energy is converted into thermal energy which will heat up the material in the conveying chambers of the pump between rotor and stator. When the temperature rises high enough spontaneous ignitions sets in at various places in the explosive. The critical time frame for such heating typically is from five to twenty minutes. The time of transition from quick combustion (deflagration) to detonation in the conveying chambers depends on the quantity of explosive which autoignites at the same time, and may lie between milliseconds and seconds.
It is, therefore, the object of the invention to provide for pressure relief in an eccentric worm pump before a critical pressure potential is reached which may result in the explosion of an explosive being conveyed, said pressure relief taking place faster than the further pressure rise which is possible with a given drive performance and design of the pump.
The known readjustable stators for eccentric pumps neither are provided to solve this problem nor are they suitable to do so. The devices disp

REFERENCES:
patent: 3084631 (1963-04-01), Bourke
patent: 4084512 (1978-04-01), San Miguel
patent: 4458482 (1984-07-01), Vetter et al.
patent: 5035180 (1991-07-01), Purcell et al.

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