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Quotes - Engineering - SalesBlanching lines
A CIP heater where the rinse step is the big duty
A vegetable blancher is already a hot-water machine, and the soil it leaves is simple: leached starch from potatoes, peas and corn, chlorophyll and plant sugars from greens, and field grit that the washers upstream did not catch. There is almost no fat and little protein, so sanitation runs the caustic light, 0.5–1% sodium hydroxide at 140–150°F, for 20 minutes or so. The starch gel on the blancher drum, the flume walls and the discharge conveyor softens and lifts; the chlorophyll stain mostly comes off with it.
What the plant actually needs hot is the water. A blanching line is rinsed and sanitized with water at 180–190°F, held at the return for 5 minutes, and that water is made fresh on each cycle because the blancher and the cooling flume together hold more volume than any CIP tank. A 3-inch rinse header at 50 gpm taken from 60°F well water to 185°F is a 125°F rise, about 3.1 MBtu/h, which is several times the caustic duty.
So the heater on a blanching line is sized as a steam-to-water heater first, and the caustic step is the easy case it handles on the side.
A 185°F rinse at 50 gpm from well water is 3.1 MBtu/h
Fresh rinse water carries none of the warmth a recirculated caustic tank keeps, so the heater lifts 125°F on every cycle. The caustic step, at 150°F on a tank that is already warm, asks for a fraction of that surface.
The circuit: starch, grit, and a lot of hot water
Blancher CIP is short on chemistry and long on water. Pre-rinse clears the loose solids and most of the grit. Caustic at 0.5–1% and 140–150°F runs 20 minutes on the drum, flume and conveyors from a recirculating tank. The acid step is infrequent, phosphoric at about 0.5% when hard water leaves carbonate on the drum, and many lines skip it for weeks. Then comes the sanitize rinse at 180–190°F, once-through to drain or to the blancher's own sump.
Grit is the wild card. Sand and soil fines survive the pre-rinse and ride the caustic loop, where they settle in low points and abrade whatever they pass at velocity. Lines that process root vegetables see more of it than lines that process peas, and the plant's own strainers decide how much reaches the heater.
The heater: steam-to-water U-tube, strained and drainable
Our recommendation is a steam-to-water shell-and-tube, a U-tube bundle with steam inside the tubes and water on the shell side, sized for 3.1 MBtu/h at the winter inlet temperature. On 100 psig steam the tubes sit at 338°F and the approach to 185°F water is generous, so the heater is compact. The same unit heats the caustic tank loop when a valve swaps the water supply for the tank return. Shell, bundle and heads are 316L; EPDM on the head gasket is fine with the light chemistry.
Grit is handled outside the heater: a basket strainer on the inlet and a low-point drain on the shell so settled fines flush out at the end of the cycle. A gasketed plate pack is the other way to make 185°F water, but its 3–5 mm channels are the wrong place for sand, and on a blanching line we steer plants back to the tube bundle.
What to send for a blanching line heater
The rinse water is the sizing case, so the water figures come first. Add the caustic circuit as a second duty and we will confirm the same heater covers both.
- Rinse water flow in gpm and the temperature sanitation requires at the return
- Coldest supply-water temperature of the year
- Caustic tank volume, strength and temperature for the drum and flume circuit
- Steam pressure at the blancher room
- What the plant washes: root vegetables, greens, corn or mixed
- Connection type and whether the heater must drain between cycles
Call and talk it through with an engineer: 1-805-484-2992
Blanching line questions
Because the caustic recirculates from a warm tank and the rinse does not. A tank at 150°F only has to make up losses during a 20-minute wash. The sanitize rinse is fresh water, 60°F in winter, lifted to 185°F once-through at the full header flow. At 50 gpm that is a 125°F rise and about 3.1 MBtu/h, roughly four times the caustic hold duty.
Usually, yes, since the blancher and the heater rarely need full steam at the same moment: the line is down when it is washed. The question is pressure at the heater inlet when the valve opens. If the blancher header is throttled to 15 psig, the heater is sized for 250°F steam and gets larger; at 100 psig it is compact. Tell us the pressure you can hold at the heater.
Not the heater, if the strainer does its job. Sand at 5 ft/s is abrasive on pump impellers and valve seats long before it troubles a 316L tube wall, and what gets past the strainer settles in the shell rather than scouring the bundle. A low-point drain on the shell and a pull-and-flush of the bundle at season end keep it clear.
Only if the water says so. Blanched vegetables leave no mineral of their own, so the only scale is carbonate from hard supply water on the hot drum and on the heater's shell side. Plants on soft water run years without acid. Where a white film builds on the drum, a 0.5% phosphoric step at 120°F every week or two clears it, and EPDM gaskets are unaffected by it.
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