Open-top vapor degreaser

Unlike cold-cleaners, vapor degreasers lose relatively small amounts of solvent as solid waste or liquid drag-out. Most emissions are due to vapor loss and the loss level is highly dependent on operator and operating conditions. Solvent losses for a poorly operated open-top vapor degreaser may be eight or more times greater than for a well-operated unit (Branson Ultrasonics Corporation, 1988). 

Complete Control Systems for Open Top Vapor Degreasers... 

Figure 1.2 Very Small Open-top Vapor Degreaser...

This topic is covered in considerabie detail in Ref. 1, Chapter 7, pages 339 to 390 with Section 7.14, pages 390 to 395 covering open-top vapor degreasers. 

Open-Top " vapor degreasers (OTVDs) in which the solvent is heated to its normaP boiling point, and so the cleaning process is known as vapor degreasing. 

Figure 1.3 Internal View of Two-Sump Open-top Vapor Degreaser — Showing Arrangement of Sumps...

Figure 1.22 Open-Top Vapor Degreaser with Tall Freeboard Height, Located in Pit...

In the last decade of the last century, many suppliers of solvent and equipment sought to develop alternate designs for open-top vapor degreasers — which would allow their offerings to continue to compete for business. 

Figure 1.23 Sliding Cover for Open-Top Vapor Degreaser Used with Highly-Volatile "Designer" Solvents...

Said as dearly as possible, parts entering an open-top vapor degreaser are rinsed with condensed solvent before they are washed in soil-laden solvent. 

What happens in a typical open-top vapor degreaser is not static. It s dynamic, as ... 

Figure 1.37 Interior View of Open-Top Vapor Degreaser Showing Superheat Coils...

Open-top vapor degreasers are not capable of supporting vacuum, nor are exhaust blowers capable of producing it... 

As of publication of this book, essentially all open-top vapor degreasers are compliant with the design or emission requirements of the 1994 NESHAP. There are three reasons for this (1) it is and has been the law (in the US), (2) the concomitant reduction of solvent emissions has saved the cost of solvent purchase, and (3) it has been effective in meeting current workplace exposure limits. The 1994 NESHAP remains in force today. 

Figure 1.59 Use of Parts Basket with Hoist to Insert and Remove Parts from Open-Top Vapor Degreaser (Items 1 and 5)...

S. Open-top vapor degreasers constructed in the past used drinking water from city utilities for the purpose of cooling. Some of those machines survive, consuming water and discarding it after one use. 

U. Some very large open-top vapor degreasers will have two and occasionally three small compressors with the refrigeration units not centrally located. 

The calculation is validated by noting that the lowest achievable vapor concentration of n-propyl bromide in the work room is between about 8 and 16 ppm for most selections of different hypothetical open-top vapor degreasers. This is consistent with industrial experience. The calculation also is consistent with industrial experience, in that it shows that lower coolant temperatures (more refrigeration) are needed to maintain exposure at less than the stated exposure limit when the vapor degreaser is dimensionally larger. 

Though enclosed vapor degreasers of various types have been known for generations, they were not commercially attractive because the use of perchloroethylene, methylene chloride, and trichloroethylene in open-top vapor degreasers was not significantly threatened by regulatory fiat or managerial fear. 

The available solvents for open-top vapor degreasing have been trichloroethylene (Ref. 3, Chapter 20) and n-propyl bromide (Ref. 3, Chapter 21) — both of which raise concerns about their effects on human health. Few credible options have been developed (Ref. 2, Chapter 2.12.3.1) to clean these parts which don t involve emission of these hazardous materials. That is why this application was exempted from further regulation in the updated NESFIAP for Flalogenated Solvents (Chapter 1.28). 

Purpose Contain and manage normal emissions of solvent from open-top vapor degreaser Allow control of environment in which solvent contacts parts Avoid contact between solvent and air (oxygen and water)... 

The surfaces of both end caps should join smoothly to the straight pipe so that there is the least possible volume of crevices where particles, soiled solvent, and rinse fluid can be trapped. In open-top vapor degreasers, these junctions are called cove comers. 

And as to the eagerness of US-based management to pay purchase prices of three to five times that of an open-top vapor degreaser in advance of accumulating those savings and other benefits, that zeal has yet to be realized in the US by financial commitments. 

That of open-top vapor degreasers is generally similar (or less) because of the same character of halogenated cleaning solvents exposed to water and oxygen. 

This statement is based on the belief that if halogenated solvents are used within enclosed vapor degreasers, the degreasers will be operated in an airless manner by first purging the o)ygen and water which enter with the parts Without that action the solvent, possibly unstabilized, will react as it does in an open-top vapor degreaser. 

Note that the facilities shown in Figure 2.29 are neither those of an airtight or airless enclosed vapor degreaser. They are the facilities of a conventional open-top vapor degreaser enclosed within a suitable housing. 

In one sense, the airless enclosed vapor degreaser is the perfect open-top vapor degreaser because (1) no tall freeboard is required to contain solvent vapors, allowing the apparatus be compact and easily located in a work area (2) a fresh supply of pristine distilled solvent is always available for cleaning and rinsing so there is no space consumed by a second liquid sump, and no outcome where the parts are rinsed before they are washed (Chapter 1.14) and (3) no programmable hoist is required as the solvent is... 

The volume of solvent in the air vented from the externally sealed apparatus of Figure 2.29 is small. This is because the cleaning chamber (the volume within an open-top vapor degreaser) never releases its full contents of vapor. Only air saturated with solvent is released when the parts basket displaces it into the airlock on entry and entrains it on exit. The released volume is probably measured in cubic inches per cycle. Flowever, relative to the issues associated with solvent stability (Ref. 2, Chapter 11), it may be crucial to trouble-free operation. 

Yet, in another sense, this airless enclosed vapor degreaser is the anti open-top" vapor degreaser because it doesn t contain solvent emissions within its confines it emits them to be treated in a downstream process Chapter 4, or contains them within some vessel external to the enclosed vapor degreaser. 

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