Analysis of forces transmitted to the foundation by hydroextractors

Authors: J. Michalczyk, P. Czubak

Phenomena of generating dynamic forces in the foundation by hydroextractors were analysed in the paper. Two main sources of those influences -- the vibrator operation and unbalanced feed in the sieve-basket -- were indicated.

Approximate analytical dependencies for assessing the amplitude of exciting forces were derived and their verification was performed on the numerical model. (Fig. 1. Typical hydroextractor of the German production). Hydroextractors (Fig. 1) (Blaschke 1984) are used in coal preparation plants for dewatering of a wet feed. A feed is supplied, via a charge and charging cone, to the sieve basket driven by the system consisting of an engine, two belt pulleys and a long shaft (Fig. 2).

The system of a large belt pulley, a shaft and a basket together with the vibrator system is suspended on rubber shock absorbers. Two vibrators of the antiphase rotation cause an excitation of the whole system -- suspended on shock absorbers -- into the movement in the horizontal direction. Vibrations of the sieve basket in the horizontal direction assist in the shifting of feed. The amplitude of vibration in the horizontal direction is restricted by a system of rubber bumpers. Such arrangement provides an additional acceleration to the basket, which helps to detach the feed.

The feed is then received into the feed collector, while water drains to the water collector. (Fig. 2. Diagram of the typical hydroextractor). The Mining Equipment Plant WAMAG produces the vibratory hydroextractor WOW -- 1,3 (Technical-Operational 1989) of the sieve basket diameter 1.3 m. The dynamic forces transmitted to the foundation by the hydroextractor WOW -- 1,3 are estimated and presented in the paper, together with the methods of estimation of those forces in machines of a similar construction.

Forces transmitted to the foundation can be divided into two groups:

forces generated by vibrators causing the motion of the whole system in the horizontal direction;

forces generated by unbalancing of the sieve basket due to an irregular feed distribution.

The preliminary analysis as well as the investigations performed on hydroextractors at industrial conditions (Research Report 1995) indicate that forces generated by the motion of the whole system in the horizontal direction constitute more hazards.