ASTM D6224 Standard Practice for In-Service Monitoring of Lubricating Oil
ASTM D6224 Standard Practice for In-Service Monitoring of Lubricating Oil for Auxiliary Power Plant Equipment
6. Sampling
6.1 General - When taking lubricant samples from storage tanks or equipment in service, it is important that proper sampling techniques are followed. The following are some suggested guidelines for proper sampling technique and sample handling techniques. (See also Practice D4057.) The user should have written procedures to insure that samples are taken consistently according to good maintenance practices.
6.2 Representative Sampling - To be representative, a sample must be obtained either from an agitated tank or a free flowing line. A sample line should always be flushed before a sample is taken. The system should be in steady state operation. An agitated tank is one which is currently in use or is within 25 minutes of shutdown. A fluid sample is probably not representative if: (1) the system fluid is hot while the sample is cold, (2) the fluid in the system is one color or clarity in an in-line sight glass while the sample is a different color or clarity, and (3) the fluid viscosity of the reservoir fluid is different from that of the sample when both are at the same temperature. Samples should be taken in the same manner each time to allow reliable trending of oil properties.
6.2.1 It should be noted that on occasion a sample may be requested which will not be representative. At that time, sampling instructions, as specified by the requestor, must be followed. For example, a sample might be taken off the top or the bottom of a tank to check for contamination. In all cases, the sample point should be marked on the sample container.
6.3 Sample Container - Samples should be taken in a container which should be:
6.3.1 Clean - If in doubt about its cleanliness, use another container. If this is not possible, flush it out with the fluid to be sampled. Special care should be taken to ensure that sample containers for water separability, particle count, and wear debris testing are clean.
6.3.2 Resistance to the Material Being Sampled - For example, fire-resistant phosphate ester fluids will dissolve certain plastics. (This includes the liner in bottle caps.) To verify the container's resistance, if time permits, allow the sample to stand in the container and observe its effects. Aluminum foil or polytetrafluoroethylene (PTFE) make good, resistant cap liners.
6.3.3 Appropriate for Required Handling - Containers with leaking tops and glass containers improperly protected are not suitable for shipment. Stringent packaging requirements must be followed if shipment is to be made by air.
6.3.4 Appropriate for the Analyses Required - As an example, some plastic containers may not be acceptable for flash point testing (per Test Method D92) because volatile materials may leak through the container walls. Containers should be either glass or polyethylene for wear debris analysis samples (to avoid material leaching).
NOTE 2 - Some lubricant suppliers and commercial testing laboratories provide sample containers which meet all these requirements. These should be used whenever possible. If frequent samples are taken, an adequate supply of containers should be kept.
6.4 Sample Markings - A sample should be properly marked in order to track the history of a particular piece of equipment. The equipment must be identified uniquely. Markings should include the following information as appropriate:
6.4.1 Customer name,
6.4.2 Site (or plant name),
6.4.3 Location (unit number, tank number, compartment number, and so forth),
6.4.4 Equipment serial number (or other ID),
6.4.5 Oil and machine service hours,
6.4.6 Date sample taken,
6.4.7 Type of fluid sampled,
6.4.8 Sampling point,
6.4.9 Type of purification system (filters, centrifuge, and so forth),
6.4.10 Make-up (volume) since last sample was taken, and
6.4.11 Coolant additives.
6.5 Sampling of New Oil Deliveries - All sampling devices should be thoroughly cleaned before use to avoid cross-contamination.
6.5.1 Samples taken should be representative of the fluid being examined but obtained from the point(s) most indicative of gross contamination by debris and water, that is, just above the bottom of the drum or tanker compartment bottom.
6.5.2 When consignments of oil are in drums, sample them in accordance with Practice D4057.
6.5.3 In cases where the product is suspected of being nonuniform, sample a larger number of drums. Where contamination is suspected, there may be no alternative to sampling every drum.
6.5.4 For bulk consignments, each tanker compartment should be sampled. If these are clear of debris and water, then the samples can be combined for subsequent laboratory analysis of the consignment. The user may decide to perform a limited number of tests on individual compartment samples; a composite sample may be tested for other properties.
6.5.5 From tanker deliveries, individual tanker compartments should be sampled. The sample should be taken preferably from the outlet of the flexible pipework or at least from the tanker bottom valve manifold. This is important because the tanker contents can become contaminated by residual material left in the bottom valve manifold. This can occur particularly when different products are being carried in separate compartments or previous deliveries of a different product have been made to other locations without subsequent adequate cleaning and flushing. Dead leg piping should always be drained and flushed prior to sampling.
6.5.6 Bottom samples (if desired) must be collected by either a tube or thief sampler (for example, Bacon bomb). These samplers permit collection of settlings on the bottom of the containers without introducing false contamination by scraping the container lining or wall.
6.6 Preservation of Sample - Samples should be tested as soon as possible. Store the sample(s) away from strong light and as close to room temperature as possible. If the samples are to be retained for extended periods of time, special arrangement should be made to ensure that the integrity of the sample is not compromised. The special arrangement may include storing in dark amber glass bottles in a cool area.
