Coolants degreasers

Polymer Areas General purpose grade of AEROSOL OT surfactant. Non-Polymer Areas Used by a variety of industries for application in wetting, spraying, fire fighting, dust control, emulsion lubricants and coolants, degreasing, dry cleaning, etc. 

Coolant flows through closely spaced turns of pipe positioned to control the vapor level of the degreaser. These can consist of either a helical coil positioned in an offset compartment leaving a clear sidewall within the degreaser body or multiple passes can be provided around the inside perimeter of the tank. 

Check condenser coolant flow or temperature, or both. Adjust as necessary to ensure that the vapor level does not rise above the design or operating level and to minimize condensation of moisture from room air on the condenser coils. Check that all coolant and heating lines are free of leaks and the water separator is functioning properly to prevent contamination in the degreaser. 

The same operating conditions observed with degreasing equipment should be followed with stills. Proper operation of devices controlling vapor levels, liquid temperature, and the condenser coolant system should be ensured (refer to Table 4 for recommended vapor thermostat settings). 

Vapor degreasers have two distinctly different sets of demands for coolants ... 

While these two demands are complementary, they are not fulfilled at the same location in the vapor degreaser. Although a user may use the same source of cooling to fulfill both demands, separate streams of the same coolant (refrigerant) are used each at the same temperature (probably ), and almost certainly at a different flow rate. 

Coolant (passes through cooling colls In vapor degreaser) Water A brine... 

In designing a cooling system for a vapor degreaser one has to be conscious of the two sets of demands, and select a coolant (and the refrigeration system to produce it) that simultaneously meets both sets of demands. Purchasing two different refrigeration systems with two different... 

Selection of Coolants-Keeping Solvent In and Water Out of the Degreaser... 

Designers of vapor degreasers normally use only a single coolant fluid for each machine, with two different coolant loads (flows at the same temperature) directed to each set of coils to achieve the intended different results. This outcome is shown in Table 1.9. 

The equipment arrangement of Figure 1.35 shows how it is recommended to feed two different coolants to each set of coils in a vapor degreaser. 

In this way, the vapor leaving the vapor degreaser is contacted with the coldest coolant, thereby effecting the greatest possible reduction of solvent content in the emitted air at that upper location. This is shown in Figures 1.32 to 1.35. 

The two basic requirements for refrigeration are to (1) dry parts well and quickly, and (2) keep solvent within the degreaser. The selected coolant is one which efficiently allows attainment of the desired internal temperature and allows the degreaser to fulfill those requirements. 

Solvent Containment — The selected coolant in the secondary cooling coil will provide a concentration of solvent in the work area no more (and hopefully less) than the posted exposure limit when the emission from the degreaser is diluted with normal ventilation. Examples are given in Table 1.8. The combination of both requirements are given in Table 1.9... 

There are two causes for the inadequacy of the cooling effect (1) reduction of coolant supply for whatever reason, or (2) overlong separation of the center area of the vapor degreaser from the cooling coils adjacent to the degreaser walls. The former cause is an operational affair the latter cause is that the cooling unit is undersized for the combined width of the two sumps of liquid solvent. 

One can test the integrity of the vapor barrier by measuring the temperature in the center of the degreaser at the level of the freeboard area (above the vapor barrier). It should be significantly lower than the normal borUng point of the solvent — with the understanding that it will not be as low as the coolant temperature. Should it approach the former high value, the vapor barrier has been destroyed should it approach the latter low t ue, the vapor barrier is sufficiently intact. 

So the width of the hypothetical degreaser can be no more than whatever width causes the vapor temperature at the centerline to rise from the freezing point of the coolant to the maximum allowable temperature (-21°C and 26°C respectively for trichloroethylene — a 47°C rise). 

The point of this calculation is that a large degreaser used with one degreasing solvent can probably be used with another solvent and another coolant with the same loading of parts without violating the EPA guidance about centerline temperature. Obviously, the two solvents may impose other concerns. 

If a coolant with a lower freezing point had been chosen, such as calcium chloride (FP = — 52°C), the width of the degreaser could he increased without violation of the EPA guideline about emission control so as to accommodate larger baskets of parts. Obviously, that would substantially increase the energy costs for providing chilled coolant. 

The important point in Table 1.11 isn t just that there are preferred values for the coolant and freeboard air temperatures. The important point is that these values affect the temperature at the centerline distance from the degreaser... 

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. 

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