MIL-STD-1330D(SH) APPENDIX D
w/ Change 1
D.4.2 The specially machined dishes concentrate the sample to a small area that is within the focal point of the ultraviolet light source used by the SQM. The theory of OSEE is that some very clean surfaces, such as stainless steel, illuminated by an ultraviolet light source will emit electrons from the surface that are measurable in the form of current. As the surface is contaminated, the electron emission decreases reducing the measured current. An exception to this rule is that in rare instances, such as some surfactants, the current can increase. Properly machined and cleaned evaporating dishes will measure similarly. Likewise, properly machined and cleaned evaporating
dishes when uniformly contaminated with a known standard will also measure similarly. Therefore, comparing the results from a 5 ppm standard (with or without baseline) to the results of effluent or waste solvent can be used to quantitatively determine a go-no-go acceptance criteria. However, the electron emission is not linear, and therefore, empirical determination of the exact quantity of non-volatile organic residue cannot be determined by this method. Also, if the current increases more than an established amount, it is an indication that a contaminant other than oil and grease is present, which is considered a failure requiring recleaning.
D.4.3 Baseline can be applied as specified in Table X. The acceptance criteria of 5 ppm above baseline is established by evaporating 1.5 mL of unused solvent (baseline) followed by 1.5 mL of 5 ppm standard. The effluent or waste solvent is comprised of the unused solvent contaminated with as much as 5 ppm, therefore, only 1.5 mL of this solvent is needed for the analysis.
D.4.4 This analysis method uses three different laboratory standards: 7.80 mg TEP 2190 oil in one liter of
CFC-113 or HCFC-225 solvent, and 1.75 mg Krytox 240AC grease in one liter of HFE-7100 solvent. Each standard is applicable only to the solvent used during the actual cleaning process, except HCFC-225G and HCFC-225M can be used interchangeably as standards, and will hereafter be referred to as HCFC-225. Consistent with previous
practice, all laboratory standards are normalized to the measured response from 5 ppm hydrocarbon oil in solvent.
For the HFE-7100 standard, Krytox 240AC grease was used as the contaminant because of its solvency in HFE-
7100. However, Krytox 240AC grease has a higher sensitivity to OSEE, and therefore requires less contaminant to produce a measured response equivalent to 5 ppm hydrocarbon oil.
D.5 Apparatus.
D.5.1 The following is needed to perform OSEE analysis. Apparatus needed to prepare the 5 ppm laboratory standard is not listed, but needs to be adequate to prepare the standard as specified in D.9.
a. A Surface Quality Monitor (SQM), Model SQM 200 with sensor 60262, with 0.25-inch diameter aperture installed, for measuring residue on the evaporating dish by OSEE. The instrument can be purchased from Photo Emission Tech., Inc., (805) 499-7667. Note that "Surface Quality Monitor" is a trade name. However, since it is the only instrument of its kind capable of performing this type of analysis and is patented, the trade name is commonly used.
b. Evaporating dishes manufactured per Figure 4. With a vibro-etch tool or equivalent, mark the side of each dish with a letter or number to uniquely identify each dish.
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