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MULTIPLE STAGE CLEANING REDUCES NEW SOLVENT PURCHASES & SAVES MONEY
Let your dirty solvent do your dirty work. That's the principle behind multiple-stage cleaning. Whether you are cleaning printing presses or automotive parts, multiple-stage cleaning can reduce your costs for solvent purchases and disposal.
When one container of solvent is used for cleaning, the solvent becomes dirty with the soils that it removes from the parts, decreasing its ability to clean well. With multiple-stage cleaning, dirty solvent removes most of the soil, while the clean solvent of the additional stages thoroughly cleans the parts and brings them to specification.
Solvent use decreases because the solvent is used longer before it is discarded. When only given a cursory look, multiple-stage cleaning appears to use more solvent. Not so. While you need extra containers of solvent for the added cleaning steps, all the solvent lasts much longer than it would if used in a single cleaning step.
Using multiple-stage cleaning can also making drying times more consistent. After the dirty cleaning of the first stage, the cleaner solvent in the later stages evaporates at a consistent rate.
Determine the number of stages that work best for your operation:
Often only two or three stages are appropriate. Multiple-stage cleaning can be accomplished with flushing, immersion, sprays or a combination of these. The first stage can be used as a presoak.
A three-stage cleaning process works like this:
Stage 1: Majority of the soil is removed using dirty solvent.
Stage 2: Soil, left after the first stage, is removed using partially dirty solvent.
Stage 3: Any remaining soil is removed by the cleanest solvent.
When the solvent in the stage-1 container becomes too dirty, empty it. Refill the container with the solvent from the subsequent stage; for example, the solvent from stage 2 becomes stage-1 solvent. Refill stage 3 with fresh solvent.
Industry Example No. 1
Anagram, a flexographic printer, used one bucket of solvent to flush unused ink from the printing decks. They developed a three-stage cleaning process for their printing presses.
Using all three stages takes them an extra four to six minutes per deck. Often using only their first two stages is sufficient.
Savings: $28,200 per year through reduced solvent purchases and disposal costs. Reduces solvent waste by almost 120 drums per year.
Industry Example No. 2
Windings Inc., a manufacturer of electric motor stators for industrial control, medical and avionics applications, and power generation, converted two vapor degreasers to cold solvent dip tanks, constructed two stands for drying parts, and changed operating procedures eliminating the final stator cleaning step on 85% of the units made.
Windings converted its two existing vapor degreasers to two-stage dip tanks by disconnecting the sump heaters and increasing the height of the divider between sumps. A pre-clean step was added to remove water-based machine coolants or any gross oil contamination after machining. Pre-cleaning also was used to remove gross oil contamination in the final cleaning of assembled stacks after honing. The pre-clean step, using petroleum naphtha provided under a service contract with Safety-Kleen, eliminates water build-up in the sump and the corresponding risk of recontaminating parts with water. It also slowed the build-up of oils in the solvent.
A new cleaning cycle for assembled stators was developed, including these steps:
- pre-clean in naphtha
- soak two minutes in the dirty sump, and hand agitate
- drain and transfer to the clean sump
- soak in the clean sump for 10 minutes with ultrasonics
- transfer to a drying table for manual blow-off with compressed air to remove and recover excess solvent
- one hour of forced-air drying
With the exception of the drying steps, the old vapor degreaser cycle time was similar to the new cleaning cycle.
Cost: $1,000 one-time equipment cost
Savings: Solvent purchases reduced by $11,000 annually.
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