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Quotes - Engineering - SalesDairy heavy soils
Where the soil is nearly all fat, the pre-rinse carries half the duty
A continuous churn, the cream ripening tanks that feed it, and the buttermilk and butter-oil lines downstream are coated in fat at 80% or better. Below about 95°F that fat is a solid, and a rinse that arrives cold does nothing except move it around. Most of the soil in a butter plant can be floated off with warm water alone if the water is warm enough, so plants that run a pre-rinse at 110–120°F for 5–10 minutes go into the caustic step with a light duty, while plants that pre-rinse at ambient hand the whole fat load to the caustic and wonder why 2% is not enough.
The caustic step then saponifies what the rinse left. Fat this heavy pushes sodium hydroxide toward the top of the range, 2–3%, and the temperature toward 160–175°F; concentration without temperature leaves a greasy film in the churn barrel and on the working section. Milkstone is a secondary concern on cream equipment, because cream is not held hot for long, so the acid step runs a couple of times a week to clear the mineral the buttermilk leaves rather than every cycle.
The heater we build sits between the CIP tank and the churn circuit and must deliver two things: warm pre-rinse water quickly, and strong caustic at 165°F or more. Sizing it is the subject of this page.
Two heating jobs, one heater, and the pre-rinse is the bigger one
Bringing 2,000 gallons of rinse water from 60°F to 115°F in 15 minutes is a 3.7 MBtu/h duty. Holding 3% caustic at 165°F through a 30-minute churn wash is a fraction of that. Size the heater for the rinse heat-up and the caustic step takes care of itself.
The butter plant circuit
Churn and silo circuits are tank circuits: a CIP tank of 2,000–5,000 gallons, a supply pump, and spray devices in the vessels at 25–100 gpm each, so total circuit flow runs 100–300 gpm. The buttermilk and cream lines wash as line circuits at 70–120 gpm. Warm pre-rinse at 110–120°F for 5–10 minutes, caustic at 2–3% and 160–175°F for 30–45 minutes, an intermediate rinse, and acid at 0.5–1.5% and 120–140°F two or three times a week. Many butter plants finish with a hot-water hold at 180°F before the churn is restarted.
Fat is the fouling story on this circuit. Saponified fat and emulsified free fat return to the tank, and when the tank cools between washes the soap floats and the fat re-solidifies on anything cooler than 95°F. The heater's shell side, warmed by steam on every cycle, is not where it settles first, but the solution-side head and the suction line to the heater can carry a grease ring that needs an occasional look.
The heater for it
A tank-recirculation steam heater, steam-to-solution U-tube in 316L with steam inside the tubes, sized for the pre-rinse heat-up rather than the caustic hold. Taking 2,000 gallons of water from 60°F to 115°F in 15 minutes is about 3.7 MBtu/h, which at 15 psig steam condenses roughly 3,800 lb/h; with 50 psig at the heater the bundle gets shorter. The same unit then holds 3% caustic at 165°F against vessel losses with its control valve well turned down, so the valve needs good rangeability.
Caustic at 3% and 175°F is at the aggressive end of what CIP ever asks of a heater, and 316L handles it without comment. The head gasket is EPDM unless the acid step uses hot nitric, in which case FKM. A 1-inch tube bundle is our preference on this duty: the slightly lower shell-side velocity is accepted in exchange for a bundle that sheds soap better and pulls more easily. Mill finish is standard; churn circuits are rarely treated as sanitary loops.
For a churn or cream circuit, send us
Because the pre-rinse heat-up usualy sets the heater size, the water figures matter as much as the caustic figures.
- CIP tank volume and the makeup water temperature in winter
- Pre-rinse target temperature and how fast the tank must reach it
- Caustic strength, 2–3%, and the hold temperature, 160–175°F
- Circuit flow in gpm for the churn, silos and lines washed from this tank
- Steam pressure at the heater inlet
- Acid chemistry and how often the acid step runs
- Clearance available to pull a bundle
Call and talk it through with an engineer: 1-805-484-2992
Butter plant questions
Almost always because the pre-rinse is cold or the caustic is not reaching 160°F. Fat that was never softened in the rinse becomes the caustic step's whole job, and sodium hydroxide at 140°F saponifies slowly however strong it is. Check the pre-rinse temperature at the spray device and the caustic temperature at the churn inlet. If both are low, the heater is undersized or starved of steam, and that is a heater question we can answer from the tank volume and gpm.
Yes, and that is the normal arrangement on a butter plant CIP set, with the heater on the supply line from whichever tank is being pumped. It must then be sized for the rinse heat-up, about 3.7 MBtu/h for 2,000 gallons in 15 minutes, which is larger than the caustic duty. Plants that size the heater for caustic alone end up with a pre-rinse that takes 45 minutes to warm, and the whole cycle slips.
It can coat the solution side if the circuit sits cold between washes, and it shows as a slow drift in outlet temperature over weeks. Because our caustic is on the shell side with the bundle removable, you can see it at a shutdown and the shell drains between cycles so less of it settles. We size with a fouling allowance of 0.001–0.002 so the circuit holds temperature between inspections.
The heater sees every chemical the circuit runs, not just the fat. Caustic at 3% and 175°F, nitric or phosphoric at 140°F on acid days, and hot rinse water all pass through it, and 316L takes all of them at CIP strength. Carbon steel appears only on the utility steam head where no solution touches it. The real 316L risk in dairy is chloride from brine; the salt from a butter churn's salting step is light and is rinsed away before the caustic step.
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