TABLE OF CONTENTS Taking the oil sample is critical, especially if the sample will be analyzed for coarse metal particles. These larger heavy particles tend to settle out quickly and are more readily removed in the filter. Therefore their distribution in a machine's oil system is not at all uniform. Taking the sample from the active oil stream, and in the same way each time, is required to get good trending results. The selection of the sampling point and method should be made with inputs from the lab. Each person who will take samples should go through a short course on taking samples. Most labs have specialists who will spend a day in your plant selecting sampling points and methods, training personnel, and recommending special valves and sampling techniques.
There are generally three sampling methods used today. A vacuum pump with disposable plastic tube is the most common way to take a sample from a non-pressurized sump. An ordinary valve or special oil sample valve can be used to sample from a pipe or side of sump. Care must be taken with valves to flush out the dead leg which is always there. Also, one must be careful to avoid taking a sample from an area of no flow, such as at a sump wall or, worse, from the bottom of a sump where heavy debris settles and accumulates. A sample from the sump bottom will contain particles which are "ancient history" and are of no interest...
