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Monday, September 25, 2006
A - Agitation

Question/problem:
What types of movement can be employed to enhance cleaning?

Solution:
This addresses the second variable "AGITATION" in Alconox's acronym BATHCARD, factors that contribute to successful cleaning. Click here to learn more.

AGITATION
Soaking is a cleaning method that involves no agitation. Other cleaning methods involve some form of agitation which can be performed through manual (cloth, sponge, brush), ultrasonic, flow-through clean-in-place (for pipes, tanks and tubes), spray cleaning (a dishwasher, for example), and high-pressure spray cleaning. In general, increasing agitation means increasing cleaning effectiveness, particularly when trying to remove heavy, bulk soils.

Agitation is a factor in detergent choice. High emulsifying, high foaming cleaners are more effective for cleaning processes with low levels of agitation and longer cleaning time. These include the manual, soak and ultrasonic processes. Likewise, low foaming, high dispersing cleaners are suitable for high agitation cleaning with short contact time as found in spray washing, parts washing and when using spray CIP systems, etc.

Presoaking generally enhances cleaning, particularly if soils are dried or baked onto the part to be cleaned. As stated above, it is always preferable, to clean as soon as possible after soiling to avoid dried or baked on soils.

Time constraints and volume of parts being cleaned affect choice of an agitation method and with it detergent. When a large number of parts must be cleaned quickly, then a fast, high-agitation method, such as spray washing, with an aggressive detergent is preferable. Likewise, when cleaning fewer parts or batch-continuous quantities of smaller batches rather than the large quantities from continuous manufacturing of parts, ultrasonic soak cleaning with a milder detergent is more appropriate for the wetting and emulsifying mechanisms that work well in ultrasonics.

The cleaning methods referred to above are discussed below in greater depth:

Manual cleaning - typically chosen for small-volume batch cleaning. High levels of cleanliness that can be achieved by manual cleaning. Though, much depends on the consistency of operators performing the cleaning operation. That's why, rigorous operator training and retraining should be arranged. In addition, there is a
need for clearly written cleaning procedures and training procedures. It is even a good idea to go so far as to certify operators in different cleaning methods with periodic recertification.

Soak cleaning - usually chosen for cleaning small volumes, of parts, when time is not of the essence. Typically a slow process, soaking is not labor intensive. Care should be taken, however, when cleaning delicate parts. Because soaking involves longer cleaning times, there more opportunity for corrosion to occur. As a result, soaking is best suited for cleaning robust parts.

Ultrasonic cleaning - particularly effective on small parts with blind holes and crevices that are inaccessible by spray cleaning. This process is essentially soak cleaning enhanced by ultrasonic sound energy. It greatly accelerates the speed of cleaning and can greatly improve cleaning in small spaces or crevices. Ultrasound helps disperse and mass transfer the cleaner. It replenishes fresh cleaning solution to surfaces of parts being cleaned.

Ultrasonics also accelerates corrosion, so care with substrates and cleaners with suitable inhibitors is required. Ultrasonic cleaning involves more expensive equipment and is typically suitable for larger volume batches and where a higher level of cleaning is required.

Clean-in-place by circulation system - typically used for piping or small tank systems where a spray clean in place system cannot be used. It is also an appropriate method for cleaning filtration systems in which filters cannot be accessed by spray nozzles.

Spray clean-in-place - typically used in larger tank systems where the increased efficiency, achieved by using less cleaning solution, justifies the cost of the spray system. Spray cleaning of tanks provides more reliable and more complete coverage of the tank. An immersion cleaning system may not reach the top of a tank and additional manual cleaning may be necessary.

When choosing a detergent for tank systems, remember that a detergent that performs well for soak cleaning may not perform as well in spray cleaning. Therefore, if you anticipate scaling up a current system to a spray clean-in-place one, consider using a spray-cleaning detergent that performs adequately in soaking operations.

The choice of a cleaning machine depends both on size of batch and size of parts being cleaned. As batch size increases and ultrasonic machine may no longer be efficient. It often makes sense to choose some form of cabinet, under-counter or floor standing washer.

For very high-volume parts washing, a conveyor cleaning system is a suitable option. Parts, placed on a conveyor, are cleaned using spray nozzles as they pass through the system.

Spray cleaning systems are very good for parts and surfaces that are readily accessible. They are not as effective when there are blind holes and small crevices. When cleaning high volumes of parts, where it makes sense to use spray cleaning, investigate spray under immersion.

For cleaning very, large parts, for example, vehicles or very large assemblies (where an operator can physically move around the part), it makes sense to use a power spray wand or handheld pressure spray device to clean part exteriors.

(A - Agitation)