Pipes are produced in various thicknesses that have been standardized. Each pipe wall thickness is given a name pipe in the form of schedule number, not in the form of actual pipe wall thickness.
Initially, the pipe wall thickness is classified into three groups as following below:
- Double Extra Strong (XXS)
- Extra Strong (XS)
- Standard
Currently the naming of pipe wall thickness has been replaced with schedule which providing certain number, starts from 5 and 5S, then followed with 10 and 10S, so in multiples of 10 to Schedule 40 (20, 30, 40), and then have multiple of 20 such as pipe wall thickness schedule 60, 80 , 100, 120, 140, 160.
The pipe wall thickness which has schedule 40 is generally same with schedule STD pipe sizes 1/8 inch up to 10 inch. Likewise, schedule 80 is the same as the schedule XS for pipe sizes 1/8 inch up to 10 inch.
One thing should be considered is the use of pipe that has Schedule 5 and 10 are more widely used on stainless steel pipe. While the pipes which are classified as Small Bore, usually have minimum pipe wall thickness of Schedule 80, although it may have thickness more than that, it's just going to make a pipe becomes excessive strength than is needed.
Pipes are usually produced with having different length depending on the material, size and schedule. But in general the pipes are produced with having average length of 20 feet or 6 feet for pipe Carbon Steel. This length is also called as random length. Sometimes pipe which having length twice than random length are also widely available and include preferred especially for use in the pipe rack. This size is also called as Double Random Length, or equal to 12 meters.