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Quotes - Engineering - SalesDairy line circuits
Small circuit, narrow passages, no tolerance for a cool wash
A homogenizer forces warm milk through a valve gap of a few thousandths of an inch at 2,000–3,000 psi, and the shear that breaks the fat globules also drives fat and protein hard against the valve seat, the impact ring and the plunger packing. The deposit is thin, pressed in, and sits in passages a brush will never reach. It is also warm-formed rather than baked, because most homogenizers run downstream of the regeneration section at 130–160°F, so the film is fat and native protein with little milkstone. That is good news chemically and bad news geometrically.
The circuit itself is a line circuit. During CIP the homogenizer runs at a fraction of its working pressure, often a few hundred psi, so that solution moves through the valve at speed without the machine fighting the CIP supply pump. Flow matches the homogenizer's rated capacity, which on a 2-inch inlet is around 30 gpm and on a 3-inch machine nearer 70 gpm. The caustic wash runs at 160–170°F for 20–30 minutes, and because the circuit volume is small, the temperature the heater delivers is the temperature the valve sees almost at once.
We supply the steam heater that keeps that solution hot between the CIP tank or makeup line and the homogenizer, and this page is about sizing it and about the one pressure question that confuses people.
The heater sees supply pressure, never homogenizing pressure
A 2,000 psi nameplate frightens people into asking for a 2,000 psi heat exchanger. The heater sits upstream of the pump block on the CIP supply, where the supply pump sets perhaps 40–80 psi, and a 150 psig shell rating covers it with room to spare.
The homogenizer circuit
Caustic at 1–2% and 160–170°F does the main work; the fat and native protein in the valve film lift readily at that temperature, and plants that try 140°F find a gray film left on the impact ring. Acid at 0.5–1.5% runs a few times a week to deal with the modest mineral the warm milk leaves, and it matters more on the aseptic homogenizers in UHT service that run hotter. Rinses run 100–120°F before and 120–140°F after, and a sanitize step at 180°F or better is common because the valve is the hardest part of the line to inspect.
The homogenizer is washed in line with the pasteurizer on most dairies, so the heater serves the whole 3-inch or 4-inch circuit at 70–120 gpm. On a standalone homogenizer, say one feeding a cream or ice cream mix line, the circuit may be its own 2-inch loop at 30 gpm. In both cases the circuit is short and the solution returns warm, so the duty is mostly a steady temperature hold rather than a cold-start recovery.
The heater and what to watch
A steam-to-caustic U-tube in 316L, steam inside 3/4-inch tubes and solution in the shell, rated 150 psig at 250°F on the shell side. On a 30 gpm standalone loop the duty is well under 1 MBtu/h and the unit is short; on the shared 120 gpm pasteurizer circuit the same construction grows into the bundle the pasteurizer needs. Steam at 15–50 psig at the heater inlet is normal, and the control valve should be sized for the holding load so it does not hunt once the circuit is up to temperature.
Watch two things. Keep the heater on the supply side of the homogenizer, not the return, so the valve receives solution at the heater outlet temperature. And because the tiny passages make the homogenizer sensitive to anything the solution carries, the heater's shell side should drain fully with no pockets where carbonate scale can shed into the circuit. A removable bundle lets you confirm the shell side is clean when you inspect the valve.
What a homogenizer circuit quote needs
Give us the circuit the homogenizer is washed on; the heater is sized for that, not the nameplate.
- Shared pasteurizer circuit or standalone homogenizer loop
- Inlet line size and CIP flow in gpm
- CIP supply pressure at the heater, typically 40–80 psi
- Caustic and acid chemistry, concentration and frequency
- Target wash temperature, 160–170°F, and steam pressure at the heater
- Whether the circuit is treated as sanitary with tri-clamp connections
Call and talk it through with an engineer: 1-805-484-2992
Homogenizer circuit questions
No. The heater is on the CIP supply, where the supply pump sets pressure at 40–80 psi, and the homogenizer runs at reduced pressure during the wash in any case. Our standard shell-side rating of 150 psig at 250°F covers every CIP supply we have seen. The high pressure exists only downstream of the pump block, inside the homogenizer, and the heater never sees it.
Check the temperature at the homogenizer inlet, not at the tank. If the tank reads 165°F and the inlet reads 150°F, the heater is either too far upstream with uninsulated line between, or it is on the return side of the circuit. If the inlet temperature is right, the fault is chemistry or valve position during CIP, and a bigger heater will not help.
Not usually. One steam-to-caustic heater sized for the shared circuit at 70 or 120 gpm serves both, since the homogenizer only adds a small volume and a little pressure drop to the loop. A separate heater makes sense when the homogenizer is washed on its own schedule, for instance between product changes on a mix line, and then it is a compact unit for a 30 gpm loop.
For heating caustic with steam, no. Plate gaskets do not like steam-side temperature and pressure cycling every wash, and a homogenizer circuit cycles several times a day. A small U-tube shell-and-tube is just as compact at this duty and has only one head gasket on the solution side. Plate makes sense here only for recovery against the hot return.
Whatever is reliably at the heater inlet after the control valve, often 15–50 psig even where the header says 100. At 15 psig the saturation temperature is 250°F, still 85°F above a 165°F wash, so low pressure costs a little surface rather than feasibility. Measure it at the heater during a wash, not at the boiler.
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