ICAR Technical Series no. 7 - Nitra Proc.

Assessment parameters of vacuum deviceResultsThe very first measurements to be carried out were those concerning thevalue of switch on/off vacuums. We know from experience that vacuumpump input power is increasing in linear way with the increasing vacuumat a simultaneous reduction of pump performance It followed from thedependences that the difference between working pump vacuum occurringwithin the chosen range p n1– p n2and working vacuum in the milkingmachine p npshould be as small as possible The larger is the difference, thelower is the vacuum pump efficiency.The first measurement was focused on the determination of minimumdifference between the switch-on vacuum p n2and the working vacuum inthe milking machine. It was found out that if the difference drops below2 kPa, the vacuum fluctuation in the milking machine is increasing. Thisis why the value was proposed to be 3 kPa.Other two factors (volume of big air-chamber and difference betweenswitch on/off vacuums) have a fairly similar impact on the operationregime. Since an increase in the difference between switch on/off vacuumvalues is undesirable, it was adjusted to 5 kPa and an influence was studiedof the volume of big air-chamber on the length of time intervals betweenthe vacuum pump switch-ons (t b) and offs (t s) in dependence on air-flowt c [s]1401201008060401,2 m 30,9 m 30,6 m 32000 1 2 3 4 5 6 7air consumption of milking machine [dm 3 s -1 ]Figure 3. Dependence of switch-on cycle length on air-flow rate at different volumesof big air-chamber.78Conference on "Physiological and technicalaspects of machine milking"