Technical guides of Ultrasonic Vapor Degreasing Machine/Degreaser

01: What is ultrasonic vapor degreaser/degreasing?

Vapor degreaser/degreasing is the cleaning process by vaporizing solvent in condensing on the parts that is being cleaned, the process doesn’t require any water or scrubbing, instead, the ultrasonic vapor degreaser, use solvent vapors to cleanse and remove contaminants off of parts, the process is used to clean various materials during manufacturing such as plastic, glass, metal, gold, and ceramic

02: How does vapor degreasing work?

At its most basic configuration, a vapor degreaser contains two tanks that are called sumps, or three, five sumps in multiple stages in vapor cleaning, ultrasonic cleaning, ultrasonic secondary cleaning, rinsing, distillation sump, metal basket, and finned condensing coils, there is a sump boils the solvent, called boil sump, and one, two, or more rinsing sumps, also can have separated distillation tanks

As a secondary cleaning method, the parts may be dipped into the boil sump, and ultrasonic added for additional agitation.

The parts that will be cleaned are placed in a metal basket that is lowered with the machine, the basket remain above the boiling solvent and below the cooling coils, the vapor degreaser boils the solvent vapors rise but don’t escape because they are trapped within the machine by a layer of refrigeration via cooling coils.

The vapor then condenses on the surface of the parts dissolving the contaminants, as the solvent drips off the objects it removes the soils with in, this is closed-loop process, so the solvent is cycled over-and-over again, the vapors go up into the cold trap, condense and run back down into the rinse sump, the rinse sump then overflows into the boil sump, the soil stays in the boil sump and will not travel with the vapor, and will not cross-contaminate parts or the rinse sump.

Those who ware glasses will find this process familiar, it happens when someone leaves a hot room or outside, and then enters a cool room, the warmer, more humid air outside will condense as a frog on your colder glasses, once you step back inside to the dryer air, and your glasses will clear, this is essentially the same process as the term “re-flux method” warm vapors condense back into liquid when cooled

03: In which applications and industries are vapor degreasing used?

Almost any industry in which precision cleaning is paramount to the manufactured parts, vapor degreasing can be found, it is common in automotive, aviation, and aerospace, medical device manufacturing, jewelry manufacturing, and electronic assembly

Various method have been developed along the way including vapor only cleaning, vapor-spray, liquid-vapor, boiling liquid-warm liquid-vapor, spray-under-immersion, vacuum degreasing as well as ultrasonic cleaning in conjunction with almost any of these

04: What are the benefits of vapor degreasing?

The cleaning benefit of vapor degreasing is the superior cleaning that it delivers and it is a very repeatable process, not as dependent on operator technique and manual cleaning methods, the use of vaporized solvent avoids cross-contamination, which is a problem with cleaning methods that reuse solvents or cleaning solutions from part-to-part, the use of solvents enables that objects dry quickly without a secondary drying process

Although vapor degreaser solvent are generally expensive compare to other cleaning materials, they are continuously recycled in the closed-loop process, which can make it an economic method of cleaning, in addition, compared to batch or inline systems common with aqueous cleaner, vapor degreasing doesn’t require heating water, rinsing, drying parts, or treating waste water during post cleaning.

05: How to select the best vapor degreasing solvent?

With the exception of co-solvent or binary solvent degreasing, it’s important that a vapor degreaser solvent is as close to an azeotrope as possible, which means all the solvent constituents boil at around the same temperature, this ensures the formulation does not change as the solvent is vaporized and reconstituted hundreds of times in a closed-loop circle

An azeotrope (as used in the cleaning world), is a mixture of two or more liquids, whose chemistries are exactly the same in both vapor and liquid phases, there are properties of any azeotrope that are unique, for example, a binary solvent blend contains two solvents, each with its own boiling point, combining these two in a precise manner, the resulting product exhibits a boiling point different that either of the individual components and maintains that boiling point throughout the process, it acts as a single components products.

Near-azeotropes, on the other hand, will fractionate (split) the two ingredients to a small degree as they boil, although stable once equalized, the composition of the vapor and liquid phases are not exactly the same, one phase will be skewed greater with one component while the other phase will be greater in the second components, due to this, there may be small differences in cleaning performance between the liquid and vapor phases.

Now that you understand the terms, let’s look at the comparative advantages of an azeotrope versus azeotrope-like in vapor degreasing, in a near-azeotrope system, you will probably get slightly better performance with soil in one phase or the other, this could be beneficial in the vapor phase if you are restricted from using immersion due to the sensitivity of components, material, etc.

When using a near-azeotrope solvent over a longer period of time, solvent losses from either vapor escaping the cool zone or drag-out, the relative concentration will shift, depending on the composition of the solvent blend, the operation condition of the equipment, and the amount of time, the change in the component ratios may produce an unsafe operation condition, or at the very least, impede cleaning performance, for example, one component of the solvent mixture may quench the flammability of the other, so a change in the component ration could increase the likelihood of the vapor igniting

Selecting and qualifying a vapor degreaser solvent is in itself an involved topic that we will cover in our ultrasonic vapor degreaser, in short, you will need to identify a solvent that cleans your particular soil well, does not damage your parts if they are sensitive to solvent exposure, falls within your local environmental guidelines, and at the lowest possible toxicity, many companies are actively replacing n-propyl bromide (nPB) and trichloroethylene (TCE) based solvents because of the high toxicity and risk factors

06: What is the best location for a vapor degreaser?

When purchasing a new (or an additional) vapor degreaser machine, the location of the unit should be considered thoroughly to find the optimal positioning of the equipment, follow are some areas of concern to keep in mind

Space requirements/clearance: get the exact measurements of the unit from the vapor degreaser manufacturer to ensure the area in question meets the space requirements for footprint and equipment access for operation/maintenance, these items include solvent loading/unloading, refrigeration repair, water removal, heating element removal, and (possibly) separate solvent distillation process,clear access to all control panels, emergency shut downs. And power supplies is a must!

Ceiling height may be concern, especially with long vertical parts that must be processed, robotic axis options for programmed basket/part moment into and out of the unit may be restricted by ceiling height and other overhangs, if so, some unit are placed into a pit to slow the issue

Never install a vapor degreaser in an area near open flames, ovens or where arc welding is performed.

Elevation: since many newer vapor degreaser models are more efficiency and compact compared to older models, this may not be an issue for you, however, elevation is ultimately determined by the height of the model and should be taken into account for safety requirements, larger models may be fitted with stairs and rails to provide safe and convenient access

Process flow: it is always preferable to place the vapor degreaser as close to the process area as possible to maintain flow integrity, however, this is dictated by facility layout and may be possible

Drafts: avoid cross drafts at all costs, this causes vapor remove/product lass resulting in exposure to employees as well as the financial implication, drafts also named solvent loss, no drafts should be allowed around the entrance/exit working area of the vapor degreaser, common areas of drafts include air conditioning ceiling registers, doors, windows, fans, or extraction vents, you many find it necessary to construct walls around the vapor degreaser or place in a separate room.

Ventilation: since most vapor degrease solvent commonly used today have vapor that are heavier that air, a floor draft that creates a laminar flow to carry or sweep the vapor is highly recommended

Humidity: water vapor absorbed into the chemistry can be a major concerns, many of the modern formulas halogenated and water entrainment can cause hydrolysis resulting in the associated acid being formed (going acid), if your facility is humidity controlled, it will remain constant year-round and the technicians can trend the degradation of the material over time as well as keeping up with water removal, if the facility is not currently controlled, enclosing the unit in a humidity-controlled operation room should be considered

Pit Concerns: if the vapor degreaser must be located in a recessed area or pit, a general rule of thumb is that if the pit is more that 60cm deep, make provisions for it to be exhausted at a minimum rate of twice its air volume per minute, ventilate at least 10 minutes before entering the Pit area

Emergency: Plan out emergency scenarios in the area for egress / ingress, placement of safety equipment such as eye wash stations, safety showers, fir extinguishers,

07: What are the key operational checks when setting up a new vapor degreaser?

Check for solvent leaks: leaks can be in the solvent containment system, sumps. Return troughs, wand, almost anywhere the solvent travels such as lines, pumps (including system seals/gaskets), and water/solvent separator, anywhere there are welds or canisters bolts ( such as the water separator), the potential for leaking exists, besides the solvent system, the refrigeration system must be checked from the compressor through the discharge line and back to the compressor via the suction line

Verify the cooling system is functioning properly: besides leaks, the refrigeration system needs to be verified that not only is it cooling, but that it can operate adequately to handle the hat, load the generated during condensation of the hot vapors

Check set point temperature of heating system: the heating system should be checked that it is operational and can held the set point temperatures by comparing it to readings from a separate thermometer, safety temperature overloads should also be verified

Ultrasonic frequency: ultrasonic frequency commonly performed in the 20~80khz range, but can go as high as around 130khz, the lower frequencies are generally used for large parts cleaning while the higher frequencies are seen in more precision cleaning application such as very small or highly complex geometrically shaped parts, some vapor degrease may have multiple transducers, these can be outside and attached to the sump (usually the wall but can be on the bottom plate) or can be inside the sump (usually looks like a round bar extending into the fill area of sump

Test wand operation: wand operation should be checked for activation and cut-off by whatever mechanism it uses, more of the time, it is power-activated by a food switch pedal

Test movement robotics: if so quipped, any movement robotic should be checked that it follows the programming guide in time, distance, direction, correct stopping, and smoothness of operation, that there is no binding of any type

Test electronic controls: all electronic controls (touch screens, dials, buttons, switches, etc) should be verified that they can be properly activated and deactivated.

08: How to optimize the performance of vapor degreaser?

Optimize maximum condensation

Run the test board with a standard vapor zone cycle time to assure that maximum condensation has occurred (when condensation stops, the part and the vapor have reached the same temperature and will be essentially dry), record the time

At this point, cleaning has ceased, remove the parts following the withdrawal procedure and  inspect for cleanliness, if there is remaining flux residue, the cycle must be repeated

Re-insert the part next to the cold condense to chill it as much as possible to obtain a wide temperature delta between the part and hot vapor (record this length of thine for further reference).

Again, lower the part into the hot vapors, and record this time (it will probably very a bit from first circle).

Go through the withdrawal procedure and again inspect the piece, if it meet the cleanliness requirements, you’ are down, if not, repeat the cycle until clean

Verify the vapor zone cleaning procedure based on your specific validation plan

09: Evaluate supplemental cleaning steps

Since there was no restriction on wand usage, now test this along with the times recorded for vapor zone cycles

Start with using the wand (record the time of spraying) prior to vapor zone cleaning and see if that makes an improvement.

Increase the spray time a bit prior to vapor immersion to see if cleaning improves, if not, start decreasing the times to find the maximum cleaning in the shortest time

Also, try the wand spray in the same manner at the end of the vapor cycle times

Record all of these spray wand variations and times to be complied later