采取有代表性的液样，需注意哪些方面？

　　Whether the detection results of oil particle contamination are accurate and reliable depends not only on factors such as instruments and personnel, but also on whether the liquid sample taken can reflect the true pollution status of the system and represent the pollution level of the system, which is a very important part of it. It is impossible to measure all liquids in the fluid system during particle pollution detection and analysis, which requires us to take representative liquid samples. In summary, two requirements must be met: first, the collected liquid sample must represent the pollution status of the entire fluid system oil pollution; The second requirement is that the collected liquid sample must have authenticity, that is, the liquid sample must not be contaminated during the sampling process.

Factors affecting the adoption of representative liquid samples

There are many factors that affect the representativeness of liquid samples, such as the sampling container itself being not clean enough, or the failure to follow the sampling requirements during the system pipeline/liquid tank sampling process to obtain representative liquid samples, etc. Analyzing the fluid system sampling process, the main factors that affect the representativeness of liquid samples are as follows:

Uneven mixing of liquid pollutants in fluid systems or tanks. The liquid sample taken when the fluid system is under static conditions or when the system operation time is too short and the oil cannot be fully mixed evenly;
The sampling container is not clean, and the sampling equipment, liquid collection pipeline, joints, and valves are not clean or severely contaminated;
Randomly sampling without following the designed parts or prescribed methods;
Not paying attention to the environment during sampling, especially in adverse weather conditions such as wind, rain, and fog, which can introduce external particle impurities;
Improper operation during sampling and improper storage of liquid samples.

Timing for taking representative liquid samples

The timing of taking representative liquid samples is also important. If the fluid system is very clean, there is no need for frequent sampling, which wastes manpower and material resources. However, in case of emergencies, immediate sampling and analysis are required. The following are common sampling timing:

Within the specified sampling period;
During the annual seasonal inspection;
When metal debris is found in the filter element or oil during cleaning;
When disassembling, assembling, or replacing accessories that may affect the pollution level of the fluid system;
When there is a functional failure in the fluid system;
When replacing or replenishing a large amount of working fluid in the fluid system;
When emergency operations cause pollution or introduce other working media;
When the performance indicators of oil products decrease, such as decreased transparency, turbidity, discoloration, odor and other abnormalities.

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What aspects should be noted when taking representative liquid samples?