MIL-STD-1330D(SH)
w/ Change 1
f. An ultrasonic cleaning tank of sufficient size to allow complete immersion of the component being cleaned. The tank shall be heated to 160 °F for NOC or 180 °F for TSP. Tanks using NOC should have a recirculating pump system and filter as specified in 4.3.1.9. The tank shall have a generator frequency of at least 25 kHz and a
generator power per radiated surface of at least 3 watts/in2. The power per radiated surface area can be determined by dividing the total generator power by the surface area of tank bottom or side where the generator transducers are located. For example, a tank of dimensions 12 inches by 12 inches by 11 inches deep with a 600 watt transducer
mounted on the bottom has a power of 4.2 watts/in2, or
A parts washer of sufficient size to completely contain the component being cleaned. The parts washer shall completely immerse the component in the cleaning agent and shall direct cleaning agent across or through the component at a fluid velocity of not less than 3 feet per second (ft/sec). The parts washer shall be heated to 160 °F for NOC or 180 °F for TSP. Parts washers using NOC should have a recirculating pump and filter selected as specified in 4.3.1.9.
g. Equipment to dry oxygen clean parts.
h. Equipment to perform the applicable analyses as specified in 5.13. This includes clean 1-liter containers as specified in Appendix B or C to obtain the required samples.
i. Packaging material as specified in 5.16.
5.2.4 Pre-clean and rinse. Pre-cleaning should be accomplished in a well ventilated area outside of the cleanroom as follows:
a. Each component shall be pre-cleaned using a compatible pre-cleaner and then rinsed with water until all visible soil, particulate, and cleaning agent is removed. Components shall be disassembled to achieve maximum cleanliness. Components which are visibly clean may eliminate the pre-clean step and proceed directly to the final clean, verification, and rinse step as specified in 5.2.5.
b. Rinsing of corrosion resistant metals such as stainless steel, nickel-copper (monel), and copper-nickel may use Grade C water provided temperatures are less than 140 °F. At higher temperatures, or where municipal water supplies leave undesirable deposits, Grade B water shall be used.
c. When using multiple pre-cleaners, rinse between each different pre-cleaner application to prevent any harmful reaction which may occur when different cleaning agents are combined.
d. When removing difficult soils such as heavy waterproof greases, silicone greases, and fluorinated greases, most pre-cleaners will have limited effectiveness if used without agitation in a soak or ultrasonic tank. Hand scrubbing is often the best alternative.
e. Components shall be dried if the delay between completion of pre-cleaning and start of final cleaning could result in the formation of rust or other oxides. Otherwise, no specific drying step is required prior to final cleaning.
5.2.5 Final clean, verification, and rinse. Final cleaning, verification, and rinsing shall be accomplished as follows:
a. Fully immerse components in an ultrasonic tank or parts washer filled with NOC at 140 to 160 °F or TSP at
160 to 180 °F.
b. Energize the ultrasonic tank or parts washer for 5 to 15 minutes. For components such as O-rings and valve seats, limit exposure to a maximum of 10 minutes.
c. Obtain a 500 to 600 mL sample of the used NOC or TSP in a 1-liter container and verify organic cleanliness as specified in 5.13.2. If any analysis fails, replace the final cleaner and repeat the final clean, verification, and rinse process. Do not wait for the results of 5.13.2 before proceeding to rinsing as specified in
5.2.5(d). When cleaning large quantities of parts on a regular basis or when cleaning with an automated process, statistical process control can be implemented (see 6.3). Statistical process control could entail, for instance, sampling every fourth batch. If the fourth batch fails, the previous three batches also fail and require recleaning.
d. Remove the component(s) from the ultrasonic tank or parts washer and immediately rinse with Grade B
water in an ultrasonic tank, batch tank, or flowing water. The rinse water shall be not less than 110 °F for NOC and
120 °F for TSP. Continue rinsing until the effluent rinse water pH measured as specified in 5.13.4.2 is 8.0 or less, but rinse for not less than 30 seconds. The preferred rinse process consists of two rinses using an ultrasonic or batch tank as the first rinse followed by a batch tank or flowing water as the second rinse.
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