• Effects of the design of a milking unit on vacuum variations during simulated milking

      O'Callaghan, Edmond J (Teagasc (Agriculture and Food Development Authority), Ireland, 2004)
      The vacuum variations at the apex of an artificial teat during simulated milking were measured in a factorial-design laboratory test involving six cluster types, two internal diameters (13.5 mm and 16 mm) of long milk tube (LMT), three water flow rates (4, 6 and 8 l/min), simultaneous (4 × 0) and alternate (2 × 2) pulsation patterns and three pulsator ratios (60, 64, and 68%). Four of the six clusters were fitted with wide-bore tapered liners and represented all combinations of two claw volumes (150 or 420 ml) and two short-milk-tube bores (8.5 mm and 13.5 mm). Two clusters were fitted with narrow-bore liners (22 and 25 mm) that had large-bore short milk tubes and large claw volumes. The vacuum variations were expressed as mean vacuum at the teat-end during the b-phase of pulsation (TVB), mean vacuum at the teat end measured over complete pulsation cycles (TV), minimum vacuum measured over complete pulsation cycles (TVM) and amplitude of vacuum fluctuation measured over complete pulsation cycles (TVF). The highest level of TVB was recorded with wide-bore tapered liners. For a milking unit fitted with a wide-bore tapered liner TVF was reduced and TVM increased by increasing either the bore of the short milk tube or the volume of the claw. When the bore of the LMT was increased TVB, TV and TVF increased. Simultaneous pulsation gave higher TVB (P < 0.001) and higher TVF (P < 0.001) than alternate pulsation for all cluster types. The overall effects of altering pulsator ratio were significant but small in practical terms. There were significant interactions between cluster type and water flow rate and pulsation pattern for TVB, TV, TVM and TVF.