Background: why 15 inches vacuum in dairy systems

[KenWP]

Our vacuum pump runs 8 milkers at once no problem. If the vacuum was anymore the cows teats would be a foot long.

[Dale Mahalko]

Volume of air (CFM) is different from vacuum gauge rating. Need more CFM to handle more milkers, because each one burps more air into the line when you plug it in. No milkers in use, means the vacuum balancer is slurping relief air like crazy to stay at 15. Newer farms use variable frequency drive, so the vacuum pump slows down when at 15 to save energy.

I believe the CFM rating is higher for milk pipelines than bucket milkers because the milk falls straight down into the buckets, while pipeline milkers also have to lift the liquid 6 ft high or so.

And if you run the vacuum higher than 15 inches for sapping, a dairy pump's rated CFM will go down. By exactly how much requires knowledge of physics and math. Uh-oh.

[maple man]

slow the speed of the pump down wont run as hot i run at 20 inchs a week at a time

[farmall h]

Very good explanation Dale. And it is true that CFM's is what matters. More CFM, more recovery. From what I understand is that if you don't have variable speed on the motor, which is unlikely on your older dairy pumps...you can put the smallest pully you can find on the motor and that will slow it down considerably, therefore less heat generated...same cfm? Yes?