Screening is one of the tea processing operations, which separates the size of tea leaves, including length, thickness, lightness, and thinness. The most commonly used screening method is to separate long and short, followed by coarse and fine. Screening for light, heavy, and thin is less commonly used. According to the different motion forms of screening, it can be divided into three types: round screening, shaking screening, and floating screening.

Round screening machines are divided into drum round screening machines and flat round screening machines. The inlet end of the sieve hole on the drum of the drum round screening machine is small, and the outlet end is large, divided into several gears. Due to the rotation of the drum and the inclination of the body, the tea leaves flow along the edge of the drum wall and scatter. The tea strips that cannot pass through the sieve hole will flow out from the tail end according to the inclination of the drum. This is a rough screening method, generally used for the first screening of raw tea to preliminarily determine its quality.

There are differences between a flat round sieve and a lifting sieve. Tea leaves move in a flat rotation motion on the sieve frame as the sieve surface rotates, allowing shorter and thinner tea strips to pass through the sieve holes, while thicker and longer ones remain on the sieve surface and gradually move in a circular motion to flow out from the tea outlet. The flat circular sieve mainly separates length and size, and the processing process needs to be repeated 3-4 times. The initial separation of the length or size of tea leaves is called sieving, which further separates the length or size of the sieved tea leaves and compensates for the insufficient sieving requirements, which is called sieving.

The shaking sieve machine is a screening machinery used to separate the thickness of tea strips and the round shape of tea. It is divided into reciprocating shaking sieve machine and vibrating shaking sieve machine according to the motion mode.

A vibrating screen machine that vibrates the sieve mesh back and forth. According to the number of screening beds, it can be divided into double-layer vibrating screen machines and single-layer vibrating screen machines. Used to distinguish the thickness of strip shaped tea and the long and round shape of round tea, and can remove the round tea head and the tendon stem. It consists of a transmission mechanism, a screening bed, and a buffering mechanism. During homework, the sieve bed is driven by the crankshaft and connecting rod to move back and forth, causing the screened tea leaves to move from high to low on the slightly inclined sieve. Meanwhile, due to the support of the sieve bed on the upright spring steel plate of the buffer mechanism, the elastic force of the spring steel plate not only causes the sieve bed to move back and forth, but also produces slight up and down jumping. This composite motion (shaking) causes the tea leaves on the sieve to stand upright, with small vertical particles passing through the sieve holes and descending. The coarse ones move towards the lower exit on the sieve surface, thus separating the thickness or roundness of the tea leaves and playing a role in shaking the head and causing cramps.

Vibration vibrating screen machine, a vibrating screen machine that vibrates the screen up and down, consists of a frame, exciter, screen bed, and buffering device. According to the form of the exciter, it can be divided into electromagnetic excitation and mechanical excitation, with the latter using the rotation of an eccentric block as the vibration source. The buffering device is a cylindrical spiral spring. Under the excitation force generated by the exciter, the sieve bed vibrates up and down, causing the screened tea leaves to stand upright and bounce on the sieve surface. The small ones pass through the sieve holes and move downwards, while the large ones move towards the lower outlet. The vibration frequency of electromagnetic vibration vibrating screen machine is 50 Hz, and the vibration frequency of mechanical vibration is around 15 Hz.

Float screening machine, a tea screening machinery used to separate impurities (such as light yellow flakes, stem bark, etc.) with a density similar to that of tea leaves. Composed of a frame, transmission mechanism, and basket shaped screen frame. When doing homework, the screen frame vibrates up and down while slowly rotating horizontally, causing the tea leaves to bounce up and down on the conical screen inside the screen frame, distribute evenly, and gradually move from the periphery to the middle. Heavy and high-quality tea leaves fall first after being thrown up, constantly contacting the screen surface and easily falling through the screen holes. Slightly lighter impurities then fall down, leaving very little contact with the screen surface and moving to the middle through the tea outlet, thus meeting the screening requirements. According to the number of screen frames, they can be divided into one machine one screen type and one machine two screen type.

The common feature in the structure of tea screening equipment is that they all have mesh screens. There are two types of screen mesh: woven screen mesh and punched screen mesh. The former has poor screening uniformity, but is woven with galvanized steel wire, which is easy to obtain, simple to manufacture, and widely used. The latter has better screening uniformity, but has a smaller effective area, higher cost, and less application.