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44 SMT Magazine • January 2015 solvent might evaporate out of a vapor degreas- er. We ran several degreaser trials to better un- derstand how 1233zd(E) behaves in a degreaser and what kind of changes in design may be needed to the degreasers, if any. Our test results showed that with a few mod- ifications a typical degreaser can be run with very low loss rates with 1233zd(E). The major requirements for the degreaser are that it has both primary and secondary coils (free board coils). The operating condition of the coils may have to be modified. The primary coils should be operated at around 0°C and secondary coils should operate at about -20°C. Low emission vapor degreasers manufactured by most va- por degreaser manufacturer can be operated at these conditions. With these operating condi- tions we found the solvent loss is equivalent to that of other solvents that are currently run in low-emission vapor degreasers. Since the solvent will be shipped in con- tainers such as refrigerant jugs, solvent will be charged and discharged through a closed-loop system. It is also recommended that centrifugal pump to recirculate the solvent be located near the bottom of the rinse sump to avoid cavita- tion or a non-cavitating pump such as a dia- phragm pump can be used. Older degreasers with no secondary coils have to be retrofitted with a set of secondary coils and in some cases circulation pumps may have to be changed in order to avoid cavitation. Some other retrofits have to be performed on a case-by-case basis. Stability Studies The chemical stability of 1233zd(E) with and without the presence of water, with metals and fluxes, is another important factor to be consid- ered in the identification of a next-generation solvent. To test this we used a set-up shown in Figure 2. Chilled water-cooled condensers were connected to small flasks and the solvents were boiled in the flasks and refluxed back to the flask. This test continued for two weeks. In the test, solvent is boiled with water alone and in the presence of various metal coupons such as stainless steel 304, cold-rolled steel, gal- vanized steel, copper, aluminum, monel, inco- nel and titanium. The coupons were partially immersed in the solvent which allowed us to look at the state of the coupons at the inter- face of liquid and vapor. At the conclusion of the test the coupons were observed visually for rusting or pitting and the remaining solvent in the flask was examined for breakdown products including chlorides and fluorides which are good indicators of breakdown of solvent. Tests showed that there was no increase of chlorides and fluorides in the solvent over the baseline and no other degradation products were formed indicating that the solvent is quite stable under these conditions. The test coupons also showed no rusting or pitting. Similar tests also contin- ued with addition of solder flux in the liquid and in that case also solvent showed excellent stability under these adverse conditions. Figure 2: Reflux test study set-up. an aLTErnaTIvE SOLvEnT WITH LOW GLOBaL WarMInG POTEnTIaL continues artiCle