DTY is one of texturing yarn and one of its application is to produce covered yarn. According to different raw material, it can be classified as риштаи бо полиэстер пӯшонидашуда ва риштаи пӯшидашудаи нейлонӣ.

The covered yarn always consists of DTY and spandex. The spandex inside and DTY outside. When name the specification, the spandex first and the outer DTY next. Like 2070, 20 means the specification of spandex and 70 means the specification of DTY.

It is also available that the combination of covered yarn including one spandex and two DTY. In this case, it named риштаи дукарата пӯшида, and the specification usually write as 207070, 207575. The number 20, 30, 30 refer to the yarn respectively. But actually, it will also be wrong if the factory don't want their craft to go to public sometimes. Then they will write another number to place the true specification. It is also normal and common. 

When DTY finishing doffing, the worker will use yarn shelf trolley to transport it to next workshop. There is a another step before it go on the covering machine. It is named spooling. To move the yarns to another smaller tube so as to fit the covering machine.

Spooling is at it's own workshop. After spooling, there will be a trolley to transport the yarn to another workshop and distribute to every spindle on covering machine.

Then put every tube on the top of machine, prepare the spandex at the bottom roller, then run the machine. During high-speed running, skilled operator will use a special tool to lead the yarn through each part. The thread mouth will finally lead the covered yarn to wrap on the tube.

Because of another process, the cost of covered yarn will be higher than air covered yarn. Of course, their application are not exactly same.