1-805-484-2992
Quotes - Engineering - SalesThe other end of the circuit
The return line is where the heat leaves and the drain limit applies
Every gallon the supply heater warmed comes back. Recirculated caustic and acid return to their tanks and lose only a few degrees; the rinses, the burst rinse between steps and, on a single-use skid, the spent solutions themselves go to drain at 130 to 170 F. Plumbing codes and most sewer authorities stop discharge at 140 F, PVC and CPVC drain lines soften above it, and a plant running ten cycles a day sends several hundred thousand Btu down the pipe with each cycle.
The parent page mentions rinse recovery in passing. This page is about the return-side exchanger: where it sits, what it has to survive, how the recovered heat is used, and the numbers that say whether it pays.
Cooling and recovering heat on the CIP return
The drain limit and where the cooler goes
The cooler sits on the return line after the return pump and the return RTD, so the temperature that proves the cleaning is measured before any heat is taken out. From there the return is routed by the matrix either to a solution tank or to drain, and the drain leg passes through the exchanger. A return tank ahead of the cooler turns a 300 gpm burst that lasts four minutes into a steady 60 gpm, which lets the exchanger and the fresh-water side be a fifth the size. Where a plant will not add a tank, the cooler is sized on the burst flow and the fresh water is stored instead.
A quench valve blending cold water into the drain is the alternative; it wastes the heat and the water and suits only a plant with one small cycle a day.
Recovering the heat
The best sink for the heat is the next fill. Fresh water going into the pre-rinse tank or the rinse tank at 55 F passes counter-current through a plate against the 165 F return and comes out at 130 to 140 F, which is the pre-rinse temperature the next cycle wanted anyway. On 1,000 gallons of final rinse that is about 700,000 Btu recovered, or 700 lb of steam the supply heater does not have to make, and at ten cycles a day the plate pays for itself in months. The return leaves the plate at 85 to 95 F, under the drain limit with no trim water. The full cycle that produces this return stream, pre-rinse to final rinse, is explained on our how CIP works page.
- Plate in 316L, counter-current, 10 to 15 degree approach at both ends
- Fresh water side on level control from the rinse tank, return side from the return tank
- Trim cooler on tower water only for the hours the rinse tank is already full
Living with what the return carries
The return carries fat, protein, spent cleaner and whatever came off the tank walls; the first rinse of a cheese vat carries curd. A standard chevron plate with 3 mm gaps blocks within weeks on that; a wide-gap or free-flow plate with 6 to 12 mm channels passes it, and a straight-tube exchanger with a basket strainer on the return passes anything. The exchanger itself is cleaned by the cleaner: the caustic return runs through it every cycle, so it seldom needs its own program, but it drains fully so soil does not settle between cycles.
The common mistake
Putting the return cooler ahead of the return temperature sensor. The controller sees 138 F on a return that left the circuit at 168 F, decides the caustic step never reached temperature, and extends the cycle or fails the batch. The sensor goes on the return line first and the cooler after it, and the drain leg only. Call and talk it through with an engineer: 1-805-484-2992
CIP return cooling conditions
Here are the conditions a return-line cooler is sized to, covering the fluid, the recovery option and the cleaning cycle. Measure them against your skid and send the return flow and temperature with your request.
| Condition | Detail |
| Fluid | Final rinse and post-rinse water; spent caustic and acid on single-use skids; carries soil, fat and suspended solids from the circuit |
| Flow range | 50 to 600 gpm return, intermittent, at the circuit's CIP flow |
| Temperatures in / out | 130 to 175 F in; below 140 F to drain, 100 F where the plant wants margin |
| Hold | None; a return tank smooths the intermittent flow |
| Utility | Fresh water filling the pre-rinse or rinse tank; tower water as the trim |
| Approach | 10 to 15 degrees water-to-water on a plate; 20 on a shell-and-tube with wide spacing |
| Construction | Gasketed plate with wide-gap or free-flow plates; straight tube with a return strainer where solids are heavy |
| Finish / class | 304 or 316L, mill finish; sanitary only where the return re-enters a sanitary tank |
| Recovery | 60 to 70 percent of the rinse heat into the next fill |
| CIP / SIP | Cleaned by the return flow; opens or drains for soil removal |
Common FAQs
Most plumbing codes and sewer authorities set 140 F. Plastic drain piping softens above that as well. A return cooler or a heat recovery plate brings the return to 85 to 120 F before the drain.
60 to 70 percent of the final rinse heat on a counter-current plate into the next fill. On 1,000 gallons at 165 F that is roughly 700,000 Btu per cycle, or about 700 lb of steam.
A standard chevron plate, yes, within weeks on a soiled return. Use wide-gap or free-flow plates, or a straight-tube unit with a strainer, and let the caustic return clean it every cycle.
Only on the rinse legs. Caustic and acid return to their tanks warm and stay there. Single-use skids send everything to drain and need the cooler on the whole return.
Related
Applications
Sanitary CIP Heaters
The steam-to-solution heater on the skid, its steam trim, and how the tank count changes what it has to do.
+ Learn More
Applications
3-A CIP
Which CIP heaters are product-contact equipment, what the symbol changes, and when it is money wasted.
+ Learn More
Applications
Industrial CIP
Bigger duties, stronger chemistry, flanged ends and a 400 F rating for cleaning loops that never see food.
+ Learn More
