In order to obtain authentic and representative liquid samples, special consideration should be given to whether the system pipeline is in a turbulent flow state when selecting sampling points. At this state, the liquid sample exhibits intense agitation, causing the particles in the liquid sample to be fully suspended and evenly distributed.

1. Principles for selecting sampling points for system pipelines

The selection of sampling points for system management should consider the needs of fluid system management monitoring based on convenience of use. The location and quantity of sampling points should be comprehensively considered based on the characteristics of the fluid pipeline. When selecting, special requirements for hydraulic system pollution control should also be taken into account, such as pollution sensitive areas, areas with the most severe pollution, and areas with high pollution generation. The selection of sampling points for system pipelines should consider the following principles:

• The number and location of sampling points should meet the needs of comprehensive monitoring of various pollutants in the fluid system setting. Each fluid system must have a sampling point that can represent the overall pollution level of the system;
  
  
• The selection of sampling points should meet the requirements of authenticity and representativeness of the system working fluid;
  
  
• The selection of sampling points should be adapted to the sampling method and solid particle pollution measurement equipment;
  
  
• The selection of sampling points should have good visibility, accessibility, operability, and maintainability, making it easy to connect sampling containers or online particle counters;
  
  
• The sampling point should be selected at a location where the working fluid has good fluidity.
  
  

2. Common sampling methods for system pipelines

There are two forms of sampling points for system pipelines: container sampling and online sampling. Container sampling is widely used due to its economy, simplicity, and convenience; Online sampling reduces the risk of secondary pollution by directly passing the liquid sample through the particle counter for detection, thus reducing the transmission link of the liquid sample. Both forms have their own advantages and disadvantages, and it is necessary to make the most of their strengths and avoid their weaknesses to do a good job in container sampling and online sampling in the system pipeline.