When Do I Change the Solvent?

Bromothane™ cleaning agents are extremely stable and can be used for weeks or months inside a well-tuned vapor degreaser. Since the solvent is constantly being distilled and recycled, it remains clean and pure indefinitely. While there is the need to perform acid acceptance tests on a weekly basis, overall the maintenance is pretty minimal.

So when do you change the solvent? Hardly ever. The real issue is not the solvent -- which remains clean and pure indefinitely -- but the collection of debris at the bottom of the sump. After a while it builds up and the machine becomes too dirty to operate efficiently.

In a standard degreaser, the contamination accumulates in the boil sump. This is the first chamber in the cleaning cycle. It is the spot into which the dirty parts are placed when they first go into the machine, and it is here where the worst contamination will aggregate.

Figure 54.1: Simple Vapor Degreasing System

In general, the boil sump on a busy machine should be cleaned quarterly. Symptoms to watch for include a change in the color of the solvent. The solvent in the boil sump will have a high concentration of dissolved contamination, to the point of tinting the solvent yellow or beige. Additionally, at the bottom of the boil sump will be a large collection of insoluble junk -- like solder balls, metal filings, labels and chewing gum -- which will need to be removed. It's time to clean the machine.

Cleaning a degreaser normally involves a process called a boil-down. This simply involves distilling (boiling) all the solvent out of the system and -- rather than returning it to the rinse sump -- recapturing it in a pail or a drum for re-use. When the last few liters of solvent remain at the bottom of the boil sump, the heat is turned off. Any residual waste solvent and the solid contamination is cleaned out by hand and disposed of as a hazardous waste. The whole process may take a day on a big and dirty machine.

In more sophisticated machines, a recirculating pump is installed on the boil sump to refresh the solvent in the boil sump and to remove particulate. This will extend the periods between boil-downs.

Once the machine is ready to be returned into service, the old (but clean) solvent which was recaptured during the boil-down process is dumped back into the machine.

Check with your machine manufacturer for their thoughts and recommendations.

A Note About Gloves

In general, skin contact with Bromothane solvents should be minimized, but it is almost unavoidable during solvent change-out processes. Impervious gloves and protective clothing are a mandatory requirement if there is any potential for skin contact. Gloves, splash goggles, aprons (when handling open drums), and safety shoes with steel toes also are highly recommended.

Here's a really good web site which has excellent technical data about the huge array of glove choices available on the market. It's organized by the Office of Radiation, Chemical and Biological Safety (ORCBS) of the Michigan State University, so it's not tied to any one manufacturer or brand. When you identify a chemical it suggests the best type of glove to use. In the color chart, you're looking for gloves rated in white or green.

Updated: February 15, 2006
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