BLOG | pipe SDR and wall thickness
18 March 2022
We regularly receive questions about SDR; what does pipe SDR mean? What does it have to do with the wall thickness? How is it calculated? Users of mobile pump systems need to be prepared for all kinds of situations. Therefore, having a good understanding of the equipment, including the piping system is important.
Pipe SDRLet's begin with the abbreviation SDR, this stands for Standard Dimension Ratio. By this we mean the ratio between the outside diameter of a pipe and its wall thickness. This information is important because it determines the maximum pressure the pipe material can handle.
SDR pipe calculationThe calculation formula is simple SDR = D/s (where D is the outer diameter; and s is the wall thickness). The lower the SDR number, the more pressure the pipe can withstand. Further, with a higher SDR number the pipe is lighter in weight and easier to handle.
For example, lets imagine a 6-inch HPDE pipe has a nominal outer diameter of 160 mm and a minimum wall thickness of 4,85 mm. The SDR is then 33, using this number the maximum allowable pressure can be calculated (we will discuss this in detail in a next blog).
SDR pipe wall thicknessWhen working with mobile pumps, we use HDPE pipes with pressed-in quick couplings. The maximum pressure is not determined by the SDR number, but by the hose clamp around the socket of the couplings. BBA Pumps tests the HDPE pipes including quick couplings at maximum pressure, choosing the SDR wall thickness with the lightest weight and best suitability for mobile use.
Which SDR is best for HDPE pipes under full vacuum?BBA Pumps recommends the use of HDPE pipes only on the discharge side of the pump. It can be the case that a vacuum could also develop in the discharge pipe. Whether the HPDE pipe can withstand this depends on various factors such as the PE quality, the wall thickness, the height and even the duration of the negative pressure. In general, when a vacuum is possible, we recommend that a SDR of 17 or lower should be selected.
Written by Henno Schothorst