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SAMPLING REQUIREMENTS.- Activities that produce LOX from on-base LOX plants must sample generating units for odor and purity after each addition, or if on continuous operation, once each 24 hours. The tank functioning as a receiver must have a sample taken every 90 days or when contamination is suspected and forwarded to a designated test site for analysis. Base storage tanks are tested for odor each week, and a sample of the contents sent to a designated
test site for analysis in accordance with table 5-2. LOX trailers must be sampled when
con-tamination is suspected and LOX converters must be sampled after any
acciclent/ incident. Samples must be forwarded to a designated test site for analysis.
Table 5-2.- Liquid Oxygen Storage Tank Sampling Schedule SAMPLE TAKING.- In order to exercise rigid control over the quality of LOX manufactured by the Navy or civilian contractors and to test for suspected contamination, a sample must be taken from the LOX container. Figure 5-10 illustrates the equipment and setup using the G-276 LOX sampler. Samplers are prepared at depot maintenance activities and shipped to the using activities, as required. Depot preparation includes the separation of valve, adapter, and cylinder; baking and evacuating the cylinder for 1 hour, and flushing once with gaseous oxygen; and finally, while still in the oven and still evacuated, the cylinder is filled to 20 psi with gaseous oxygen. The valve is then closed and the cap installed, and then it is shipped to the using activity. There are several precautions that should be observed while you are sampling. Observing these precautions will help to ensure a representative sample. Do not sample from a trailer hose. Use only a short connection between the tank and sampler. A few feet of copper tubing, three-eights
Figure 5-10.- Sampling. inch in diameter, attached directly to the tank drain outlet, or trailer fill-drain outlet, is recommended by current directives. All flare fittings must be perfect- without dents, scratches, or toolmarks. Do not use any antiseize compound on threads or any cleaning compounds on sampler parts. Contamination will result. A sampler received without residual pressure probably leaks. Such samplers should be rejected and returned. Just before sampling, remove the cap from the sampler valve; open the valve to release shipping gas pressure, then reclose. Next, remove the valve by disconnecting the adapter from the nipple, and place the cylinder upright in a holder. Attach the separator and line assembly to the tank drain or fill-drain outlet. Using a trailer pressure of 10 to 20 psi, let the LOX flow into an open container, such as the receiving vessel shown in figure 5-10, for at least 30 seconds to purge the line. Adjust the pressure to obtain a quiet, uniform, full flow from the separator outlet tube. Wipe the frost from the separator outlet tube, and immediately insert the outlet into the sampler tube and fill it. The filling will take approximately 1 minute. When liquid splashes in droplets over the top, the tube assembly is full. The sampling tube holds about 180 milliliters (6. 12 oz) of LOX, which produces a maximum pressure of 300 psi when vaporized in the closed sampler. NOTE: During the filling operation, the operator should wear a face shield, hat, gloves, and other protective equipment as excessive pressure will violently throw LOX from the tube assembly. As soon as the sampler tube is filled, remove the separator from the sampler assembly and install the adapter to the cylinder. Close it tightly with end wrenches, making sure that the valve is fully closed. Turn sampler upside down for a few minutes to allow liquid to flow from the sampler tube into the cylinder. Immerse the valve of the cylinder in water to check for leaks.
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