With the MPI compliance Date a year ago, some farms are still not compliant.
There is a hesitancy which is understandable given the complex nature in working out the best solution for each farm. Very rarely are 2 farms the same.
Here are some popular options to consider in cooling milk to compliant levels.
- CHILLED WATER SYSTEM. (Direct online)
These are generally the cheapest option with most running during milking times (on demand).
Running on demand will require larger refrigeration motors to cool the milk instantly as it passes through the plate cooler.
It is prudent with these systems to look at the possibility of slowing the milk flow through the plate cooler, as the more time the milk takes to pass in the plate cooler, the colder the milk will be.
Some will have optional heat recovery, generally giving hot water at around 50 to 60ᵒC. This will make a saving, but as it makes the warm water during milking, it may not have had time to heat adequately before a hot wash after milking.
Chilled water units operate safely at between 4 and 7ºC, so you can expect milk to enter the Vat at between 6 and 9ᵒC, over the milking period.
- GLYCOL SYSTEM (direct online during milking)
Effectively the same as Chilled water as above, although Glycol runs much colder, down as low as -3ᵒC.
You will get a colder milk temp for a start, but depending on the equipment size, you may well find that a chilled water system will give the same outcome.
A couple of things to be mindful of with Glycol systems.
Firstly the concentration of Glycol and water mix. If the solution becomes diluted for any reason, this alters the freezing point, so the freezing point becomes higher, leading to the possibility of freezing up in the plate cooler, possibly damaging the plate cooler and contaminating the milk. While this may seem unlikely, after 30 years in commercial refrigeration, have seen this far too many times.
It is essential to have regular maintenance to ensure the solution is kept at the correct ratio.
Secondly, if you are operating at or below 0ᵒC, the milk flow should be constant. Being held up in the plate cooler for too long could freeze the milk.
- CHILLED WATER OR GLYCOL BULK STORAGE
Either system can be used as a means to store cooling energy as a liquid in a holding tank.
This has the advantage of being able to run the systems off-peak or outside milking times to reduce peak electrical loads and use smaller equipment running over a more extended period to achieve the cooling capacity during milking.
The main drawback of this is efficiency or wasted cooling energy.
Given that you need about 20,000 litres of chilled water for an approximately 400 cow herd, if the storage tank is not insulated, then the question is, how much energy are you wasting, or more importantly, what is the financial cost?
Without insulation, the heat loss from a storage tank could be as high as 25%, especially if the tank is above ground in the sun and wind. This will drive the cost of cooling a lot higher than it needs to be and may well negate any off-peak savings.
You may sink the tank in the ground, that’s better, but soil temperature is still well above the chilled water temp, you’re still wasting energy, cooling down the soil.
- ICE BANK
These have been around for many decades and have proven themselves to be a reliable form of stored cooling.
The space required for an ice bank is about a quarter of that of chilled water, in that the energy to turn ice back into the water is very high, so you get a lot more cooling from a Kg of ice than you do a Kg of water.
It follows that you have a smaller footprint for an ice bank, so they are more accessible to position around the shed.
Traditionally they have been deemed inefficient in the fact they usually hold a large capacity of ice with the ice covering the cooling circuits; this reduces the heat transfer so the thicker the ice, the less efficient they become.
Systems like Snapchill™ are not traditional; they build ice then “burn” it off at every milking. This reclaims lost efficiency and generates more efficiency by producing large quantities of hot water at 82ᵒC in the process.
- PRECOOLING UNITS RUNNING OFF EXISTING VAT REFRIGERATION
This is an option that can save costs by not needing a refrigeration unit for your pre-cooling system.
There is merit in this when using it for cooling storage, shifting the milk cooling to before it hits the vat, rather than after it’s in the Vat. The refrigeration run times shouldn’t be too much different.
It can be used for either Chilled Water, Glycol or Icebank, but with the savings comes a risk.
With all your milk cooling running of one refrigeration system, should you have an equipment failure, then you lose ALL milk cooling until a repair is made. We would consider this a temporary measure to get compliant but look at another refrigeration unit for your pre-cooling or vat when possible.
With a separate pre-cooling system, the risk is reduced as you will always have some cooling available.
I hope this information is useful when considering pre-cooling options.
There is always more than one option to suit your requirements; it is essential that you get the best option, so you are not just spending to bridge a gap, but rather making an investment that saves you in the short, medium and long term.
If you want to find out more on what may suit you
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COOLER. FASTER. SIMPLER