The equation of cavitation characteristic is (2):

     Adjusting of pump work and cavitation drift is carried out by the change of the pump capacity and suction height. But it is known, that the change range of the capacity is strictly individual for every pump. In this work we will base on characteristic of the pump ЦНС-300-120/600, which is widely used in the mining discharge plant. The capacity of this pump can be changed within the limits of 200?400 m3/h. The depth of mine is adopted to be equal to 560 m, and diameter of suction pipeline is 0,31 m.

     By the joint solution of equations (1) and (2) in relation to Hвс and putting in the values known in hydraulics we will get (3):

     where k is a coefficient of positive suction head, k = 1,25;

     is the coefficient of Darsy, , calculated by the formula Sheveleva (4) at flow speed in the suction pipeline V1,2 m/s:

     When V<1,2 m/s the value of is received by multiplying formula (4) by a correction coefficient k1, represented by the empiric formula: (5):

     Root-mean-square error of calculation k1 with a formula (5) in the change range of the flow speed V=0,2-1,2 m/s makes .

     - the critical positive suction head calculated by the formula Rudneva (6):

     where n is rotational speed of a driving wheel of the pump ЦНС-300-120/600, n=1475 min-1;

     c is positive suction head of the pump specific speed (7):

     The pump specific speed is calculated by a formula (8):

     Qн=300 m3/h, and Hн=60 m are accordingly capacity and head, which are developed by the first stage of the pump in the nominal mode;

     Putting the values in formulas (7) and (8) we will get c=753,6 min-1.

     Changing the values of the capacity from 0 to 400 m3/h we get dependence Hвс=f(Q) shown on figure 1.

     After treatment of the graph Hвс=f(Q) by the least-squares method we get empiric dependence (9):

     Root-mean-square error of calculation of Hвс.р. with a formula (9) in the change range of pump capacity Q=0-400 m3/h is 5,65%. Because we are interested in the working change range of capacity of pump ЦНС-300-120/600 within the limits of 200-400 м3/ч, where root-mean-square error is 5,02%, we consider that this error is possible.

     Calculations on the basis of formulas given above are represented in table 1.

Table 1 - Finding empiric dependence by the least squares method.

     The following formulas (10, 11, 12) calculate coefficients A, a and b as in the table 1:

     Dependence of Hвс.р=f(Q) is represented on figure 1.

Figure 1 - The graph of dependences of calculation suction height with the formula (9) Hвс.р=f(Q) and operating with a formula (3) Hвс=f(Q).

     Thus, this empiric dependence (9) can be used in the future for calculation of control set points when creating defence block from cavitation of suction pipeline of the discharge plant.

     When working with this theme the system of automatic diagnostics, which will provide the required defence and control of operating parameters of the head discharge plant, will be developed.

     Summarizing experience of exploitation, it is necessary to mark that permanent readiness of automated discharge plant to work can be provided by careful care, observing conducting repairs terms, revisions of pump equipment and timely technical service. Skilled service is basis of reliable work of the apparatus.

The list of literature

     1. Алексеев В.В., Рудничные насосные, вентиляторные и пневматические установки: Учебн. пособие.-М.: Недра, 1983 - 381с.

     2. Гейер В.Г., Тимошенко Г.М. Шахтные вентиляторные и водоотливные установки: Учеб. для вузов – М.: Недра, 1987 – 270 с

     3. Толпежников Л.И., Автоматическое управление процессами шахт и рудников. М.: Недра, 1985 – 352 с.;

     4. Шевчук С.П., Повышение эффективности водоотливных установок - К.: Техника, 1991. - 53 с.

     5. Попов В.М., Рудничные водоотливные установки. - 2-е. изд., перераб. и доп. - М.: Недра, 1983 - 304 с.

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