Parlour testing a must for tip-top performance
Parlour testing is important
for optimum performance
and is also a requirement of
many milk buyers.
Jessica Buss met a milking
machine technician on farm
to find how to improve
CORRECTLY adjusted vacuum levels and pulsators can reduce cell counts and milking times – and even well maintained parlours need testing to ensure the best settings are used.
So warns Mark Scrivens, Axient milking machine testing manager.
When testing Arthur and Stuart Leas 6:6 abreast parlour at Oak Farm, Ridley, Tarpoley, Cheshire, Mr Scrivens found that the vacuum was running too high; the gauge was inaccurate and it had gone unnoticed.
To test the vacuum he put the parlour in the milking set-up. The running level should be 51Nm; at Oak Farm it was 53Nm and this meant there was an increased risk of teat damage and mastitis.
"It doesnt matter what the gauge reads, provided you check it stays the same, but they can be adjusted to give the correct reading at the correct setting," said Mr Scrivens.
The servo regulator which controls the vacuum was only five years old. Arthur Lea had replaced the old deadweight regulator which would not have met current British Standards because it was slow to react to vacuum changes. But Mr Scrivens warned that many were still used.
He found that the sensitivity of the regulator in use was adequate. It was also sited away out of the pump room which avoided it sucking in oil fumes.
Once the basic settings were correct the pump itself was checked. Mr Scrivens replaced the broken drain flap on the interceptor water trap that could have caused some air loss.
Each section of the plant was tested for air leakage. First the airline was checked. The initial reading was 100 litres loss of vacuum a minute, double the British Standard permitted, but a leak found and corrected on one of the feeders lowered the reading.
Dirt, corrosion or too many corners in the airline are also common causes of vacuum loss, but dirty pipes could be avoided by cleaning the line. Mr Scrivens recommended regular vacuum line washing with water, especially following a split liner.
Then the milking system was tested. Here leakage is usually low despite many joins, said Mr Scrivens. The Leas parlour had only 15 litres/min of air loss. Each claw is designed to have a 10-litre bleed, here it was acceptable at 9 litres/min.
Normal range for pulsator leakage was 25-35 litres for each point. Here it was slightly higher but acceptable.
"The pulsation system is working adequately, with 55 pulses a minute, but a shorter rest phase will speed up milking a little and that will be better for the cow. A longer exposure to vacuum causes more damage," said Mr Scrivens. These electronic pulsators were easily adjusted in the control box.
Pulsators must also be set for the type of liner fitted, he added. Mr Lea always replaced liners with the same type. But Mr Scrivens warned that if a different type was chosen pulsators must be reset.
For optimum pulsation, check teat cup liners stay in line with the markers, he added. "Even a 1/8th of a turn can cause teat damage."
Mr Scrivens also explained that pulsator filters needed to be cleaned out as frequently as the parlour environment dictated. "Dust in filters can extend milking times. Air pressure is needed to close liners – when filters are severely blocked the liner doesnt shut and that can increase mastitis."
A pulsation graph indicated that the pulsation phases were not fully maintained because of the poor vacuum reserve in the glass milk lines; replacement with stainless steel should be considered, advised Mr Scrivens.
Mr Lea said that replacing the milk and vacuum lines would take place soon, but to install 4cm (1.6in) stainless steel milk lines with welded joints and a plastic vacuum line was a large investment. Work to ease cleaning of the parlour had been more pressing this summer.
Mr Scrivens added that a marked improvement could be made with little expense by replacing the milk lines with stainless steel of the same external diameter of 3cm (1.2in). That would increase the milk line capacity by 50% and improve the pulsation.
This need not be expensive – second-hand stainless steel pipes were available, and the increased capacity would be essential if the parlour was to be extended. It would also allow faster milk transfer and water movement during circulation.
A plastic vacuum line would also be an improvement, but would cost a few hundred £s and fitting.
Pulsator filters need regular cleaning to perform well, says Mark Scrivens.
Pulsation graphs showed a shorter rest phase would speed milking.
• Test the vacuum – too high and it will cause teat damage.
• Check for air leakage which could cause vacuum loses.
• Poorly adjusted pulsation can slow milking and harm the cow.