What causes fouling in a dairy pasteurizer?

Protein denaturation and burn-on at the heating surface, which depends on the surface temperature rather than the bulk temperature. Lowering the medium temperature and adding plate area usually lengthens run time considerably.

Why must pasteurized product be at higher pressure?

So any leak in regeneration flows from pasteurized into raw rather than the reverse. It is a regulatory requirement, and it constrains pump placement and valve arrangement across the whole system.

Can one frame do regeneration, heating and cooling?

Yes, separated by connector grids. It saves space, piping and cost against three separate exchangers and is the normal arrangement on HTST systems.

What about whey and high solids streams?

Higher fouling and often higher viscosity. The Free-Flow plate handles solids-bearing streams, and generous cleaning access matters more than on fluid milk.

What is the realistic saving from pre-cooling milk?

It depends almost entirely on your incoming water temperature and how much water you can deliver at peak. Send those two numbers with your peak milk flow and the saving can be worked for your farm rather than quoted from a brochure.

Where does the Fre-Heater fit on a dairy farm?

After the refrigeration system, not instead of it. It takes heat the condenser would otherwise reject into the yard and puts it into the hot water system. It is covered under Heat Recovery.

Do we need double-wall construction on a milk cooler?

Preference does not come into it - the local authority decides what has to sit between the two media. Settle that with them while you are still specifying, not when the inspector arrives: a double-wall unit is physically larger for the same duty, so it changes the layout as well as the price.

Dairy Processing | Mueller Heat Exchangers

Dairy Processing

Pasteurizing, Cooling and Whey Duty

Milk, cream, whey and cultured products all foul heat transfer surfaces in the same way, and all of them are made in plants where cleaning schedules run the operation.

Dairy is the market Mueller is best known in, and the equipment reflects it. Pasteurizing, product cooling, whey concentration support, CIP heating and cold water supply are all covered by the same two technologies.

Pasteurizing. Regeneration, heating and cooling sections in a single frame, with the pressure differential rule keeping pasteurized product above raw product at all times. Regeneration efficiency is where the operating cost sits.

Protein burn-on. Run length between cleans follows surface temperature. A closer approach lets a cooler medium do the same job, which is frequently the single change that doubles run time on a dairy pasteurizer.

Whey and by-products. Higher solids, more fouling and often higher viscosity. Free-Flow plates and generous cleaning access matter more here than on fluid milk.

Dairy processing plant with stainless tanks and pasteurizing equipment

Typical Specification

Typical duty: Pasteurizing, product cooling, whey, CIP heating
Product contact: Type 316 stainless
Frames: Type 304 stainless, unpainted
Sections: Regeneration, heating and cooling in one frame
Pressure rule: Pasteurized side held above raw side

Fouling mechanism: Protein burn-on at the heating surface
Particulates: Free-Flow plate where solids are present
Cleaning: CIP, with frame opening for inspection
Cold water: Falling film chiller for near-freezing supply
Farm side: Pre-cooling before the bulk tank

On-Farm Milk Cooling

Pre-Cool First, Then Recover What Is Left

On-farm milk cooling is a heat recovery problem before it is a refrigeration problem. Milk leaves the cow near body temperature and has to reach storage temperature quickly, both for quality and for the milk buyer. Doing all of that with refrigeration is the expensive way.

Pre-cool first. Running milk against well or municipal water before it reaches the tank typically brings it down to within a few degrees of the water temperature. That removes most of the heat load before the refrigeration system starts, which cuts run time, energy cost and wear on the condensing unit. An Accu-Therm plate pack does the duty, and it opens for inspection and takes more plates if the herd grows.

Then recover what is left. Whatever the refrigeration system does have to remove leaves as heat at the condenser, and on most farms it goes into the yard. A Fre-Heater intercepts it and puts it into the farm hot water system instead — water you were going to pay to heat anyway for parlor washing and tank CIP.

Where a second barrier is required. The local authority decides what has to sit between the two media, not preference. Where a vented interspace is called for, the double-wall plate provides it, and any breach reports to atmosphere rather than into the other fluid.

The Water Side Decides Everything

Around two liters of water per liter of milk is the assumption behind the performance figures, and it is the assumption most often broken in practice. If the well cannot deliver that at peak flow, or the pump is undersized, or the plumbing throttles it, the milk reaches the tank warmer than the calculation predicted.

It is worth measuring the water actually available at peak rather than the pump's rated output. That one number explains most of the pre-coolers that are reported as underperforming.

Flow Profile, Not Herd Size

The number that sizes a pre-cooler is peak milk flow through it, not the size of the herd. A parlor that puts a large volume through in a short window needs more cooler, and more water, than the same herd milked over a longer period. A robot delivering a near-continuous trickle is a different problem again.

Send the peak flow and the milking pattern rather than the cow count, and the selection follows from it.

Questions on materials

The molybdenum in 316 gives it noticeably better resistance to chloride pitting, and chlorides reach a dairy plate from water, salted products and chlorinated sanitizers. 304 is fine for frames that only see washdown. If you run brine, cheese whey or anything heavily salted, tell us, because that may push the plate material higher still.

The compound has to be FDA compliant, resist swelling from milk fat and survive hot caustic and acid every day. Those demands pull in different directions, which is why one compound rarely suits every dairy duty. Send the hottest CIP step, the chemicals and their strengths, and the product fat content, and the compound is picked against all of them.

They can, when the solution is too strong, left on too long or allowed to dry on the surface. Pitting usually starts in crevices such as gasket grooves, where the chloride sits undisturbed. Follow the chemical supplier's strength and contact time and rinse properly, and the plates will last far longer than the gaskets.

Whey, acid whey in particular, is lower in pH and often saltier, so it is harder on both stainless and elastomers. Its higher solids also foul faster. Material and compound choices made for a fluid milk pasteurizer should be checked again rather than copied, so tell us the whey type and pH.

Painted frames chip under daily washdown, and paint flakes near product are a foreign matter finding waiting to happen. Rust then creeps under what is left. An unpainted stainless frame with stainless bolts is simply washed with everything else and looks the same years later. Over the life of the unit it is the cheaper frame.

It can foul and attack the water side. Hardness scales the plates, iron and manganese leave deposits, and high chlorides threaten the stainless. Since the pre-cooler sees untreated well water every milking, get a water analysis before selection so the plate material and a descaling routine are chosen with it in hand.

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Dairy Processing