MIL-STD-1330D(SH)
w/ Change 1
5.5.3.4 Large in-line volumes that will not support minimum flushing velocities should be individually cleaned and bypassed during the final flush if possible. The concern is that NOC and TSP final cleaners remove soil by displacement. In areas of low flow, suspended oil can separate from NOC or TSP and collect. If the volume cannot be bypassed, cannot be inspected and locally cleaned as specified in 5.12.4, and will collect separated oil perform
the following: isolate the volume into the smallest flushing loop possible, obtain local engineering approval (see
6.3) to pre-clean by flushing with a low foaming detergent pre-cleaner that will emulsify oil contamination, and then perform the preflush as specified in 5.5.6 prior to the final NOC or TSP flush. The pre-cleaner is used to remove oil and grease contamination, and then NOC or TSP is used to remove any pre-cleaner residue and certify cleanliness. For volumes that cannot be bypassed, but can either be locally cleaned as specified in 5.12.4 or the configuration of the volume will not collect separated oil during the final flush, such as an in-line vertically oriented flask, a separate pre-clean flush is not required.
5.5.4 Electrolytic oxygen gas generators. For systems with electrolytic oxygen generators, perform a potassium hydroxide (KOH) contamination inspection as specified in 5.6.
5.5.5 Leak-check. The flush boundary shall be leak-checked with nitrogen or Grade B water to the anticipated flush pressure. This will eliminate the time consuming clean-up of spilled or leaked cleaner. Where an oxygen clean system interfaces with a flush boundary, using nitrogen for the leak check is recommended. Any nitrogen leakage into the oxygen clean system will not cause loss of cleanliness.
5.5.6 Preflush. For new systems or systems with extensive modifications, a preflush as follows is recommended:
a. Perform a forward and backward preflush at a minimum of 3 ft/sec using Grade B water. The preflush water temperature may be elevated to not greater than 180 °F. The higher temperatures will increase the effectiveness of the preflush and preheat the system minimizing the pipe line cleaning time.
b. Outlets should be opened one at a time to help clean valve bodies and other probable pocketing areas. The flush should continue until there is no visible evidence of debris.
5.5.7 Hydrostatic test. Hydrostatic testing as specified in 5.9 should normally be accomplished after the preflush, if applicable, and before the final flush.
5.5.8 Final flush or pipe line cleaning. The final flush or pipe line cleaning shall be accomplished as follows:
a. Flush the system with NOC at 150 to 170 °F or TSP at 160 to 180 °F at the flow rate as specified in
5.5.8(b). The temperature of the NOC at the outlet of the system being cleaned shall be maintained at not less than
140 °F. If TSP is used, the system shall be preheated by flushing once-through with hot Grade B water until the desired temperature is attained. In order to prevent precipitation of the TSP, the TSP shall not be allowed to cool or remain uncirculated prior to rinsing as specified in 5.5.9. If NOC is used, it may be recirculated in the system cold and heated in place. The flush starts when the outlet temperature reaches 140 °F.
b. The fluid velocity shall be not less than 3 ft/sec. The flow rate in gallons per minute (GPM) equivalent to 3 ft/sec can be determined by multiplying the square of the pipe or tube inside diameter in inches by 7.4, as follows:
GPM at 3 ft/sec = (ID-inches)2(7.4)
c. The requirements for a back flush and the flush durations for various applications are as specified in
5.5.8(a) and Table III.
d. At the completion of the flush, obtain a 500 to 600 mL sample of the flushing medium in a 1-liter container from each outlet prior to the filter. Sampling prior to the back flush is required only if new cleaning agent will be used for the back flush. If the same charge of cleaner is used for both directions of the flush, only sampling at the end of the flush is required.
e. For NOC, visually inspect the sample for oil and particulate. If oil or particulate is present, continue flushing until no oil or excessive (3 or more particles) particulate is present. Continued flushing will allow the filter to remove the visible contaminants. If no oil or excessive particulate is present, verify organic cleanliness as specified in 5.13.2.
f. For TSP, verify organic cleanliness as specified in 5.13.2.
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