Hydraulic Fluid Sampling

and maintenance manual for the particular equipment or as directed by the MRCs. 1. All samples should be taken from circu- lating systems, or immediately upon shutdown, while the hydraulic fluid is within 5°C (9°F) of normal system operating temperature. Systems not up to temperature may provide nonrepre- sentative samples of system dirt and water content, and such samples should either be avoided or so indicated on the analysis report. The first oil coming from the sampling point should be discarded, since it can be very dirty and does not represent the system. As a general rule, a volume of oil equivalent to one to two times the volume of oil contained in the sampling line and valve should be drained before the sample is taken. 2. Ideally, the sample should be taken from a valve installed specifically for sampling. When sampling valves are not installed, the taking of samples from locations where sediment or water can collect, such as dead ends of piping, tank drains, and low points of large pipes and filter bowls, should be avoided if possible. If samples are taken from pipe drains, sufficient fluid should be drained before the sample is taken to ensure that the sample actually represents the system. Samples are not to be taken from the tops of reservoirs or other locations where the contami- nation levels are normally low. 3. Unless otherwise specified, a minimum of one sample should be taken for each system located wholly within one compartment. For ship’s systems extending into two or more compartments, a second sample is required. An exception to this requirement is submarine external hydraulic systems, which require only one sample. Original sample points should be labeled and the same sample points used for successive sampling. If possible, the following sampling locations should be selected: a. A location that provides a sample representative of fluid being supplied to system components b. A return line as close to the supply tank as practical but upstream of any return line filter c. For systems requiring a second sample, a location as far from the pump as practical Operation of the sampling point should not introduce any significant amount of external contaminants into the collected fluid. Additional information on hydraulic fluid sampling can be found in NAVAIR 01-1A-17. Most fluid samples are submitted to shore laboratories for analysis. NAVAIR 17-15-50-1 and NSTM, chapter 556, contain details on collecting, labeling, and shipping samples. NAVAIR 01-1A-17 contains procedures for unit level, both aboard ship and ashore, testing of aviation hydraulic fluids for water, particulate, and chlorinated solvent contamination. 3-11