Alright, I see that I jumped in here assuming people knew what I was talking about, so I’ll go back to the beginning.
Milk tanks are stainless steel. They do not rust, or there would be problems with America’s milk supply.
A milk truck, the ones you see on the highway, carry about 4,000-5,000 gallons, and the larger trailers carry about 7,000-8,000 gallons http://www.extension.org/faq/25769
. My 1,400 tank would be about ¼ of one of these trucks. You install the bugger, and you never move it again. I would guess it stands a little over 5 ft tall, including legs, is oval but 6 feet wide, and probably 8 feet long. Let me just say that I was traumatized as a 11-12 year old when they lowered me in it to fetch a screwdriver that made its way to the back (the tank was empty). That big.
Regulations state that the milk tank is housed in its own little room, away from the cows. This is to keep things like flies and mice away. Usually, they are cinder block buildings, but they HAVE TO BE painted white, to show dirt. Most of the time, they are windowless with the exception of one wall, which is glass. That’s how it got in the room. The floors are concrete, and have a drain in them, so the floor can be hosed off of anything, including spilled milk.
With our system, we would milk some cows, and it would go into a little 7 gallon tank, which would then pump it over to the bulk tank when it was full. It would come though some pipes and then drop down via gravity though a “sock filter” (not a real sock – that’s just what it is called). It would fall into a tray which had a “sheet filter” in it, which would gravity feed into the tank. When not in use, the tray would be removed, and a hinged lid would be closed (not sealed).
A cow’s body temperature is 101 degrees, so that is about how warm the milk is. The warm milk is coming in on one end of the tank, and the refrigerator unit is on the other end. Ever take a bath and add more hot water, but it is all at one end? That’s is what the paddles were for – to mix the milk for better efficiency of refrigeration, not to prevent the milk and cream from separating. Since it is raw milk with bacteria (the filters were just to get what little dirt might be there from the cow’s body), it needs to go from about 100 degrees to 40 degrees or less to be safe from growing that bacteria. The paddle is in the milk, but the axle goes up through the top of the tank to a motor that is sitting on top.
At the bottom of one end, not the refrigerated side, was a way for the tanker to connect up. It was like a hose bib, but about 4” in diameter at the bottom. They hook up, and then turn open a valve on the tank. Afterwards, they would hook up a motor to it that would then clean the tank.
You hear about these suckers being converted into fermenters as small dairy farms shut down. The refrigeration this is not an issue in my head. The paddles… well, there is a little bit of air getting in via the axel, but maybe the paddles are removed and it is plugged, or maybe not. How would the paddles affect sediment? The big opening on the top is my biggest worry, though, the opening must remain, it is just how it is closed that worries me. The opening at the base could not be used due to the lees, but that would just stay closed and only opened for cleaning.
- I think they miss quoted the farmer on this tank because we operated about the same size farm. Farmers work in pounds, not gallons, so I think they were working with about 800 gallons every other day, which is what we did (once, we went three days and filled it because the tanker couldn’t get there due to roads, and we had to dump it. Sad sad day). Anyway, the entry for the milk into the tank is on the far end, and the bluish thing on top is the motor for the paddles. I’m not seeing the refrigerator coils, which is a little odd. This picture was taken between milkings, so the filters are not in place.