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Quotes - Engineering - SalesMelt it off
The CIP heater behind a cream batch tank
A topical cream or ointment batch tank is the hardest tank in a pharmaceutical plant to clean, and it has nothing to do with microbes. The residue is the oil phase of the product: petrolatum, mineral oil, cetyl and stearyl alcohol, glyceryl stearate, lanolin, beeswax. It is spread thin over the wall, the agitator blades and the scraper arms by the last turn of the mixer, and it sets as the tank cools after the batch is pumped out. Caustic does not dissolve it. Caustic saponifies the fatty acid part and emulsifies the rest, and it does neither until the film has melted, which for most cream bases means the wash solution has to be above 160°F at the wall and preferably at 170°F.
That one fact drives the whole circuit. The caustic is strong, 2–3% sodium hydroxide, often with a surfactant added by the plant. The spray device has to deliver 75–100 gpm so that the wall is flooded rather than misted. The wash is long, 45 minutes rather than 20. And the heater on the CIP tank loop is sized to bring a 1,500-gallon tank of caustic to 170°F in about 20 minutes and then hold it there against a tank wall that is pulling heat out of the solution the whole time. Let the tank slip to 150°F and the wax that lifted re-sets on the first cold surface it meets, which is often the heater itself.
Keep the caustic above the melt point or the wax comes back
A 1,500-gallon caustic tank taken from 70 to 170°F in 20 minutes is about 3.75 MBtu/h. Hold it at 170°F through a 45-minute wash and the saponified wax stays in solution; let it fall to 150°F and it coats the heater bundle.
Cream tank chemistry and temperature
Sodium hydroxide at 2–3% is the working strength on cream bases, double what a protein soil needs, because saponifying a fatty-acid film consumes caustic as it goes. Plants often add a low-foam surfactant from their own program to carry the emulsified oil. The target is 170°F at the spray device, which means the heater outlet runs 5°F or so higher to cover the loss in the supply line. The acid step is light duty here, phosphoric at 0.5% and 130°F on a weekly schedule, because the mineral load from a cream batch is small.
The circuit is tank recirculation, almost without exception. Once-through would send 75–100 gpm of 3% caustic to drain every pass, and the 45-minute wash would consume more chemical than the batch is worth. So the CIP supply tank, commonly 1,000–2,000 gallons, is heated on a loop and the spray device draws from it. The final rinse is purified water at 140°F, warm enough to keep emulsified oil from breaking out on the way to the drain.
A heater that can be opened when wax wins
A U-tube shell-and-tube with steam in the tubes and caustic in a 316L shell is the right heater, and on this duty the removable bundle is not a convenience but the point. If a wash is ever cut short or the steam valve sticks, re-set wax coats the shell side, and a bundle that pulls can be cleaned on the floor with hot caustic in an afternoon. For a 1,500-gallon tank heated from 70 to 170°F in 20 minutes the duty is about 3.75 MBtu/h, condensing roughly 3,900 lb/h of 15 psig steam, and on 100 psig steam at 338°F the same duty fits a shorter bundle.
Because the solution side fouls and the steam side does not, we carry a fouling allowance of 0.001–0.002 on the shell and add surface for it. The head gasket is EPDM for the caustic and the mild phosphoric step; the shell is rated 150 psig at 250°F. Cream plants rarely treat the CIP loop as sanitary, so a mill-finish shell with tri-clamp or flanged ends is the usual build, with a 32 Ra finish available where the quality group asks for it.
Quoting a cream tank heater
Tell us about the cream base and the tank, and we will size for the melt point rather than for a textbook protein wash.
- The oil-phase ingredients with the highest melt point
- CIP supply tank volume and the warm-up time allowed
- Caustic strength and whether a surfactant is added
- Spray device gpm and wash duration
- Steam pressure at the heater
- Finish and connections the loop is built to
- Whether a bundle has coated with wax on the existing heater
Call and talk it through with an engineer: 1-805-484-2992
Cream tank questions
Because the residue is wax and fatty alcohol, not protein. Cetyl and stearyl alcohol melt near 120–140°F, but a film of petrolatum and glyceryl stearate blended with them softens much later, and caustic cannot saponify what it cannot wet. At 170°F the film is fluid and the 2–3% caustic works on it; at 150°F the wash runs its 45 minutes and leaves a translucent smear on the wall.
The shell side is coating with saponified wax every time the tank cools between washes. The caustic holds the soap in solution at 170°F, but a CIP tank that sits overnight at 100°F drops it out, and the heater bundle is the surface it drops onto. Pull the bundle and clean it, then keep the tank warm between cycles or drain it. A removable U-bundle makes the first part a half-day job.
It would open, but the gasketed plate is not where we put steam on a 3.75 MBtu/h caustic duty; the steam-side cycling is hard on the gaskets. Where a plate pack fits a cream plant is on recovery, taking heat from the 170°F return to warm makeup water. The steam-to-caustic heater itself stays a U-tube shell-and-tube with a bundle you can pull.
Yes, it is one tank circuit, and the heater does not know the diffrence. What changes is the flow: a spray device alone may take 75 gpm, but a tank with a scraped-surface agitator often adds a second device or a higher gpm to wet the arms, and the circuit may run 100 gpm or more. We size the heater on the tank warm-up and check it at the full circuit flow.
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