ASTM D923 standard practices for sampling electrical insulating liquids
SAMPLING CABLE FEEDERS
19. Mandatory Conditions
19.1 Contaminated liquid may be present in any piece of sealed equipment, cable feeder, or cable joint. In order that contaminated liquid is not discarded, do not draw off any liquid prior to taking a sample nor rinse the sampling device with liquid drawn from the sample source. Exception to the conditions will apply where a connecting line exists between the sampling point and the liquid source to be sampled. In this case, withdraw and discard a quantity of liquid approximately equal to the volume in the connecting line.
19.2 Precaution - In the sampling of oil from a high-pressure pipe-type cable feeder, exercise extreme caution when opening the valve. First connect the sampling device with the bottle in place to the sampling outlet and gradually open the valve to permit a flow of oil into the sample bottle without undue force.
20. General Considerations
20.1 Specify the location at which sampling outlets are to be installed on liquid-filled cable feeders and joints whenever sampling is contemplated and indicate on the design drawings so that samples will always be obtained at the same locations whenever sampling is repeated. In this way the history of the oil as a function of time will be comparable, since samples will always be obtained at specific locations.
21. Using the Manifold-Type Device (Fig. 5)
21.1 Cleaning the Device - With valve 3 closed and all other valves open, rinse the inside surface of the manifold thoroughly with Stoddard solvent or other suitable solvent and also the outside surfaces of the tubing that extends into the sample bottles. Screw two sample bottles into the caps, close valves 5 and 7, and purge the manifold with dry gas for approximately 15 s. Remove the sample bottles and do not use them for obtaining samples.
21.2 Sampling Procedure:
21.2.1 If there is no reservoir at the cable end remote from the sampling location, connect a reservoir of adequate oil and pressure capacity at the remote end. Close the valve on the reservoir at the sampling end to assure minimum dilution of the sample with reservoir oil.
21.2.2 Connect the manifold with the flexible metal hose to the sampling outlet and connect the vacuum and gas lines.
21.2.3 Open the sampling outlet valve and flush the manifold by opening valves 1, 2, and 7. After flushing the manifold, close valves 2 and 7 and continue draining oil through valve 1 until a quantity corresponding to the volume of the tubing between valve 1 and the location of the oil to be sampled in the joint or termination, has been drawn off. Close valve 1. Caution: Regulate the flow of oil so that a positive pressure will be maintained in the oil system. For this purpose install a gauge between valve 1 and the sampling outlet valve (see Fig. 5). The pressure as indicated on the gauge, with valve 3 open, shall be not less than 14 kPa (2 psi) if the gauge is installed at the same elevation as the sampling outlet valve. If the gauge is installed at a lower elevation than the valve, the minimum allowable pressure shall be increased by 2.8 kPa (0.4 psi) per foot of difference in elevation.
21.2.4 Screw clean sample containers into the metal caps. Open valves 4 and 5 and apply to the sample containers a vacuum of not less than 133 Pa (1 mm Hg) for 10 min. Close valves 4 and 5.
21.2.5 Open valve 1 and fill container No. 1 to 13 mm from the top. Close valve 1. Open valve 2 and repeat the same procedure for container No. 2. Close valve 2.
21.2.6 Break the vacuum with gas by opening valves 4 and 6. Remove the containers from the manifold, close valves 4 and 6, and seal and identify the sample containers.
21.2.7 Disconnect the manifold from the sampling outlet and restore the cable oil system to normal.
22. Sample Information
22.1 Attach a tag, lable or otherwise mark each sample container so that it can be properly identified.
22.2 At a minimum, include the following information: serial or identification number, and date of sampling.
23. Keywords
23.1 electrical insulating fluid; sampling electrical apparatus; sampling procedures
