The sifter separates particles by size.  Small leaves which have been rolled successfully the first time fall to the bottom and then are moved to the next process. The larger particles which fall off the end go back to be rolled again.

Green teas skip the fermentation stage and go directly to the drying room. Leaves for black and oolong teas however, are spread evenly on special raised flat beds to allow fermentation to the desired degree.  Although the process has been traditionally called "fermentation" it is actually an oxidation process that depends on tea enzymes reacting to oxygen.
Temperature control is critical.  The cooling ducts at the top of the room help maintain the desired temperature.
The chemical reactions taking place in the leaves directly affect the cup quality and determine the aroma and briskness of the brew.
Fermentaion must be strictly  regulated to produce good tea.

Next, the tea leaves travel up a conveyor belt to the dryer.  They pass through the dryer at controlled temperature for about 24 minutes or longer if necessary.  The goal is to stop the fermentation process and transform the tea into a stable product.

After drying the tea must cool down before the sorting  and grading process.   If the sorting takes place while the tea is still warm it can lose its character and bloom.
The first step in the process is passing the bulk tea through machine sorters which do most of the size grading - whole leaf, broken leaf, fannings.  They are then hand graded to further fineness.  The tea all comes from the same plant but the grading separates the leaves by size.  Broken leaves and fannings work well in teabags   while whole leaves are reserved mostly for loose tea brewing.

Note the use of bamboo trays and hand meshes  used as part of the hand sorting process after the machine sorting is done.