What Features I Should Look for
in a Vapor Degreaser Designed for Bromothane™?

Bromothane™ solvents are a great choice to use in vapor degreasers. These systems will deliver fast, reliable and consistent cleaning at the very lowest cost-per-part-cleaned. Part of the reason Bromothane™ works so well in vapor degreasers is because the solvents are all true azeotropes or near-azeotropic blends. This means they will retain the proportions of their mixtures across all the normal temperature ranges, even when distilled. This makes them ideal for use in heated cleaning systems.

There are a number of procedures you can implement with you vapor degreaser to improve quality, enhance safety and speed throughput. if you are unfamiliar with vapor degreasing, MicroCare will train you and your team on these procedures as part of our normal product stewardship program. But there also are some special features on the machines which can help with the cleaning process and keep costs down. In effect, you will be trading an increase in the one-time capital expense for a significant decrease in daily operating costs. Here's a few of the features to look for:

• Hoists. Most modern vapor degreasers larger than one-gallon machines will have an automatic hoist as an optional feature. Normally, these hoists are mounted out of the way, on the back of the machine. The operators will place their baskets of parts to be cleaned on the hoist and simply hit the "start" button. Once activated, the hoist will automatically open the degreaser, lower the parts in to it for a prescribed period of time, and then remove them. Sounds like a luxury, right?

  Not really. While an automatic hoist is simple the savings can be substantial. There are three reasons for this. First, it frees the operator to go back to work and do more productive tasks. Secondly, it lowers and raises the basket into the cleaner slowly which minimizes "the piston effect" and reduces solvent losses. Lastly, the automatic systems which operate the hoist offer more consistent cleaning results by precisely controlling the cleaning cycle.

  Figure 55.1: Hoists

  [Photo, right] The expensive and wasteful piston effect can be beaten by using an automatic hoist. A slow-moving automatic hoist allows the basket to be introduced and removed very slowly, minimizing solvent losses and saving money.

  The recommended maximum speed for work entry and removal from degreaser/defluxers is 10 ft/min. Higher throughput rates can cause vapor/air interfacial disturbances that result in high vapor losses.

  Too rapid movement of work is frequently encountered in units that involve manual work handling. Use of an automated hoist can minimize the solvent losses associated with work handling.

  Of all the options you can buy, nothing will save you more money faster than a hoist.

• Freeboard. "Freeboard" is a fancy term for the height of the vapor degreaser; specifically, the height of the sides of the degreaser over the cooling cools. Higher sides means the cold trap is more efficient and reduces diffusional losses. This means the system will retain more of the solvent vapors inside the machine, which saves money.

  Figure 55.2: Freeboard in a Typical Degreaser

  [Photo, right] Freeboard is just the height of the sides of the machine, over the top of the cooling coils. Here Greg Kitchen shows us the cooling coils in a small Unique Equipment degreaser. The vertical blue line (not in the original photo) shows the height of the freeboard. More freeboard helps reduce solvent losses and the overall cost of cleaning.

  Freeboard is typically measured as a ratio of the size of the machine. The most common dimension is the width of the degreaser, that is, the size of the degreaser's opening from front to back (not left to right, as most people assume). In the old days, a freeboard ration of 50% was considered the norm. Today, 150% is more typical and 200% is not uncommon. So, a degreaser that is fifteen inches wide should have sidewalls rising 24-30 inches above the top of the cooling coils.

  As you might expect, all this extra freeboard makes degreasers much taller than they used to be. This can be a problem for petite workers, so another option you should consider is a short but sturdy platform upon which the techs should stand when using the machine.

• Extra Chilling. Most degreasers today have three or four rows of cooling cools above the cleaning chamber. In the old days, these cooling coils were chilled with a continuous stream of tap water which produced little, if any, cooling (and how wasteful that must have been!). But solvents were cheap and nobody knew about the ozone-layer, so it was no big deal.

  Today it is a different story. Today's solvents are much more expensive and keeping them in the machine is the paramount prerequisite to getting cost-effective cleaning. Therefore, most of the refrigeration systems are modern, tightly closed systems, just like an air conditioner or your home refrigerator. Another option on most machines is an extra layer of chilling coils, which will reduce solvent losses significantly. The savvy engineer will specify both a primary and a secondary condenser system. The stronger the cold trap, the more efficiently the machine will run.

• Super Heat. Some products are difficult to clean. Their shapes or their materials of construction often result in solvent being trapped inside the part. When the part is removed from the degreaser, and lifted through the cold trap, the solvent escapes into the air. This is wasteful and unnecesary.

  A better solution is to have a layer of heating coils between two layers of chilling coils. Often called super-heat, these coils can raise the temperature of the vapors to very high temperatures -- sometimes to 150% of the boiling temperature of the solvent. This greatly enhances drying and encourages any entrapped solvent to boil out of the inner recesses of the parts.

  Every part and application is different, but anecdotal evidence suggests that super-heat can reduce solvent losses by 50% or more.

• Ultrasonics. If you're making electronics, skip this section because ultrasonics generally are not used on today's advanced electronic circuitry. But if you are cleaning small mechanical parts then ultrasonics may save you a lot of money.

  Figure 55.3: Ultrasonics Enhance Cleaning

  Ultrasonics work by blasting ultra-high frequency sound waves through the cleaning chamber of the vapor degreaser. Unlike simple vapor cleaning, when using ultrasonics the parts being cleaned are actually submerged into the solvent bath. The ultrasonic sound creates standing-waves within the solvent, which form tiny bubbles which open and then collapse at phenomenal pressures. The internal pressures in these bubbles can approach 10,000 times the force of gravity. Obviously, with these "scrubbing bubbles" the system delivers great cleaning. The Bromothane™ solvents are designed to work very well with ultrasonics.

  [Photo, above right] Below the basket of parts, the boil sump is bubbling -- almost foaming -- with ultrasonic energy. Ultrasonics can shorten cleaning cycles and help remove the heaviest contamination, but may damage fragile components.

• Computer Controls. In today's solid-state world, we strongly suggest you specify a programmable control system for your degreaser. They're cheap, their easy to use and can dramatically boost the cost-effectiveness of the cleaning system. These controls operate the hoist, adjust automatically the cooling and heating systems, activate the ultrasonic systems, monitor the health of the water separator and other adjunct systems, and can even put the machine in to energy-saving stand-by mode at the end of the workday. Most controllers can store instructions for different cleaning cycles, so you can tailor the cleaning cycle to the component being cleaned. Plus, they free up your workers to be more productive. This is a wise choice.

Then there is an accessory you do not want to buy without a very specific and demonstrable need: the spray wand. In the old days, every vapor degreaser came with a spray wand which allowed techs to blast the solvent into the components. It was kind of like having a huge, turbocharged refillable aerosol inside your vapor degreaser -- just blast away! And they work great -- they speed cleaning and improve cleaning quality, to be sure.

But spray wands disturb the cold trap, allowing vapors to escape. They also expose workers to solvent vapors and waste a lot of time. Wands also mean that your cleaning process is now dependent upon people doing a good job every time -- a dubious assertion. Our strong recommendation: don't get the spray wand. It might cost you a fortune in wasted solvent.

Updated: Dec. 21, 2004
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