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In-Situ Rinse vs. Dip Rinse

Die Cleaning Equipment and Supply customers often ask for us to differentiate between double in-situ rinse and a heated dip tank. The choice is the customer’s, but we like to share the experience of our past customers to better inform that choice.

IN-SITU RINSE – Not always the best choice for every extrusion operation

Double In-situ rinse makes sense for 16 inch and larger dies. Larger dies require longer cycle times likely to be 8-12 hours. At most, you’ll get two cycles on each tank per 24-hour day. Double In-situ rinse fills and drains the cleaning tank two times for to ensure a thorough rinse. Filling and draining may take 10-15 minutes each (10-minute fill, 10-minute drain) because of the large 400-gallon tanks. The rinse fill and drain time becomes less important because the soak times are so long. If you’re running a 12-hour cycle, adding 40 minutes to rinse fill and drain twice isn’t likely to be noticed.

When smaller dies are cleaned, the cleaning cycle is likely to be in the 3-6 hour range. Adding 40 to 60 minutes to the cleaning cycle to rinse will be noted, and operators who have elected this option have elected to use a single rinse cycle. Machines with multiple cleaning tanks may find that a cleaning tank must “wait its turn” before a rinse can commence, further increasing cycle time.

Cleaning smaller dies also influences the cleanliness of the water held for rinsing the dies. In a 24-hour day, a two-tank machine might run 4 or more cleaning cycles per tank, or 8 for the machine per day. Often, the time between “make batch” cycles is four days, meaning the rinse water will get used 32 times. The water for cleaning is not going to be very clean.

Double in-situ heated rinse is a significant increase in cost and complexity to the overall machine design and construction for several reasons. One, we use dedicated piping to minimize the pollution from caustic standing in either the fill or drain piping & pumps. In-situ rinse requires a second rinse water tank and a second pump. This rinse system alone could add 10 valves and a pump to a 360-3-1 (3 reactor tanks; one mix tank).

There is also an additional heater. Additional complexity is found in three additional analog temperature sensors (one for each rinse water holding tank and one in the heat exchanger itself), and insulation for the two-rinse water holding tanks.

HEATED DIP TANKS – The most efficient and cost-effective choice for smaller die cleaning

For operations with many dies smaller than 16 inches, whose cleaning cycle times are 3-8 hours, on average, a heated dip rinse tank is the most efficient and cost-effective choice. Baskets of dies are easily removed from the cleaning tank, dipped in the rinse tank, and moved to the breakdown area. Heated dip rinse tanks can be drained daily to ensure clean water for rinsing.

The controls are simple, there is one small pump, and one automated drain valve. The heater is protected from dry operation via a sensor. Evaporation is significant but can be topped off at any time by the operator. The rinse is thorough, and the water clean.

Overall, the water that is generated in a heated dip tank is generally consumed before it gets too dirty, and just a minimal amount goes to the waste tank. It’s simple, reliable, effective, results in lower operational cost, lower maintenance cost, and lower procurement cost.

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