Gate Scrapers - Case Study
It’s Not Such a Drag
David and Cathie Harvey have halved the water they use at washdown and plan to make further reductions with modifications to the backing gate at their dairy in Meningie, South Australia.
Their 380-400 cow dairy has a circular yard with a 15 metre gate connected to a central pillar and running on two sets of wheels. When the yard was built in 1998, David laid a 75mm water pipe under the yard and up the central pillar.
“There’s a big rubber hose that runs from the central pillar to the end of gate,” he said. “It’s looped onto the gate and hangs about one metre off ground. It’s more than two metres long and feeds into the main structural beam of the backing gate, which is also a 75mm steel pipe – galvanised on the inside – which is about 400mm off the concrete and reaches to the outside edge of the gate.
“Along the length of this beam are four outlets with little steel nipples that squirt the water on the yard.”
David said it’s critical to fit the outlets near the outer edge of the gate.
“You want to put most of the discharging water at the outer edge of the circumference,” he said. “With your lowest point being in the middle, it means all the water has to travel across the yard and that adds to the washing effect.”
The system is pressurised using the pump used for washdown. The gate washdown system is activated by a separate 75mm tap that is operated briefly as the gate moves, to keep the manure loose. It also runs when the gate returns to starting position.
“Then all it takes is a two minute washdown,” David said. “As a guesstimate, I’d say it saves about half the water we’d use at washdown. And when the cows are dried off and there’s not that much manure, we don’t have to use much water at all.”
The other big water-saver are the chains dragged along by the backing gate to break up the manure. “We started by dragging one chain but found you have to have it attached at points along the gate with wire or cable because otherwise it would drag too far behind and wouldn’t be where the water jets are,” David said.
“You need to have the chain dragging on the concrete but you also have to suspend it at quite a few points to keep it inline with the gate. And wherever you attach the chain it lifts it up and you end up with a gap. So, you put a second chain with alternate spacings so that at any time there’s chain in contact with the yard. We’ve found that works brilliantly.”
David used anchor chain because of its extra strength, weight and is double galvanised. He said the extra weight of the chains and the water has not put extra strain on the gate or its bearings because water is lubricating the whole dragging process.
David’s system was so effective it left him with a new problem. “The chain set-up is so efficient at pushing manure that when the last cows are getting into the dairy and when the gate is closed right up against it, you can have a fairly enormous wall of manure gather in front of the gate – half to a metre wide by 100mm high by 15 metres long,” he said.
He needed a drain to drop this manure into. He dug a 400mm drain in the concrete and installed a v-bottomed drain set at a fairly aggressive 5 per cent slope. “The v-shape increases the velocity of water flowing down the drain – moving the solids at twice the rate and feeding them into the effluent reuse system,” he said. “The drain is covered by a fabricated steel bar grate, not expanded mesh, to allow the solids to drop through easily.”
David hasn’t stopped modifying his system. “Next I want to run a second 75mm pipe along the entire length of the gate to recycle effluent water for the initial wash and then use clean water for the wash going backwards, that would halve our use again,” he said.
“Then we’ve got the effluent and clean water in separate systems and can then just reuse it over and over.”
Want more information?
Contact CowTime Project Manager
Department of Primary Industries, Victoria
Phone (03) 5624 2221 or e-mail cowtime.project@dpi.vic.gov.au
This email address is being protected from spam bots, you need Javascript enabled to view it.