The Standard Dimension Ratio - SDR - is used to rate pressure pipes.
Standard Dimensions Ratio - SDR
Many plastic pipe manufacturers use the "Standard Dimension Ratio" - SDR - method of rating pressure piping. The SDR is the ratio of pipe diameter to wall thickness and the SDR can be expressed as
SDR = D / s (1)
D = pipe outside diameter (mm, in)
s = pipe wall thickness (mm, in)
Example - SDR
SDR for a 10 inches ASTM D2241 - PVC Pipe with outside diameter 10.750 inches and wall thickness 0.168 inches can be calculated as
SDR = (10.750 in) / (0.168 in)
A SDR 64 means that the outside diameter - D - of the pipe is 64 times the thickness - s - of the wall.
- with a high SDR ratio the pipe wall is thin compared to the pipe diameter
- with a low SDR ratio the pipe wall is thick compared to the pipe diameter
As a consequence a high SDR pipe has a low-pressure rating and low SDR pipe has a high-pressure rating.
Pipe Series - S
Pipe series - S - is a dimensionless number related to the nominal outside diameter and wall thickness of a pipe. The pipe series - S - can be calculated as
S = (SDR - 1) / 2 (2)
S = pipe series