The ideal sieving effect of the sieving machine is that all particles smaller than the sieve hole pass through the sieve and become the under-sieved product, and the particles larger than the sieve hole are all impervious to the sieve and become the over-sieved product. At this time, the sieving efficiency is 100%. . However, due to various reasons, for example, the sieving machine contains clay and moisture in the raw material, so that the fine particles that should enter the product under the sieve stick to the coarse particles and enter the product on the sieve; or the sieve surface is used for too long. The abrasion of the holes becomes larger, which causes the coarse particles that should have entered the product on the sieve to enter the product under the sieve. There are many indicators for evaluating the screening effect. The process performance evaluation standard of screening equipment for coal sieving machine in my country (GB/T 15716—2005) stipulates that the three indicators of screening efficiency, average distribution error and total mismatch content are used as Evaluation Standards.

The sieving efficiency of the sieving machine is a technical indicator for evaluating the completeness of the sieving process. There are two main indicators to measure the screening process: production and screening rate.
The productivity of the sieving machine: that is, the production capacity, which refers to the amount of material that can be processed per unit time. Unit is t/h
Sieving machine's sieving rate: the ratio of the actual weight of the product under the sieve obtained in the sieving to the weight of the particle size smaller than the size of the sieve or sieve slit in the feed is called the sieving efficiency, which is expressed as a percentage. The sieve efficiency of the sieving machine is an indicator of the working quality of the equipment. It indicates the extent of the screening operation and the quality of the screening product.
The application principle of the above three indicators is: for the technical appraisal of newly developed equipment, the acceptance of newly put into production equipment or the inspection of important production technology, these three indicators should be used to evaluate the indicators at the same time. The daily inspection of screening equipment is not subject to this restriction.