PE PPR技术招标计算公式简介
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What is SDR and how does it influence the pressure rating of the pipe?
什么是SDR，它是如何影响管道的压力等级的？
The SDR is the ‘Standard Dimensional Ratio' and refers to the geometry of the pipe. SDR is defined as the ratio of the nominal outside diameter to the nominal wall thickness.
SDR全称“Standard Dimensional Ratio”标准尺寸比，是指管道的几何术语。
SDR被定义为公称外径与公称壁厚的比。
SDR = dn/en
Where;
∙dn is the nominal outside diameter of the pipe
∙en is the nominal (minimum) wall thickness of the pipe
∙dn 管子的公称外径。
∙en 管子的公称(最小)壁厚.
Therefore a higher SDR indicates a thinner-walled pipe at any given diameter.
这就是说，在指定的外径的情况下，越高的SDR值对应越小的壁厚。
The relationship between the SDR and the pressure rating is given by Lames formula for the hoop stress in thick wall cylinders:
SDR和压力等级的关系可以由在不同壁厚条件下的环应力所表示的公式推导出来。
s = P(dn - en) / 2 en
This can be rearranged as;这个公式也可以重新推导出下面这个公式：
s = P (SDR - 1) / 2
Where;在这个公式里，
∙s is the maximum hoop stress ；S是最大环应力
∙P is the internal pipe pressure ；P是管道内的压力。
The hoop stress is the design stress for the material, which is the (MRS) minimum required strength divided by the overall service (design) coefficient C.
环应力是按材料设计的，是指用MRS（最小要求强度，PE100的强度是10.0 MPa，PE80的最小强度是8.0 MPa）除以一个设计的系数C。
MRS/C = P (SDR - 1) / 2
or rearranging;也可以推导出下面的公式；
P = 2 MRS / C (SDR - 1)
This pressure ‘P' is then defined as the ‘Maximum Operating Pressure' MOP, or the pressure rating of the pipe.
这个压力“P”被定义为最大操作压力MOP，或者是管道的压力等级。
MOP = 2 MRS / C (SDR - 1)
Where;在这个公式里，
∙MRS and MOP are in MPa
∙ MRS和MOP的单位是MPA
Or;或，
MOP = 20 MRS / C (SDR - 1)
Where;这里，
∙MRS is in MPa
∙MOP is in bar.
Example ; What is the MOP or pressure rating of an SDR11 PE100 water pipe?
For PE100 the MRS = 10 MPa. For water applications the minimum recommended service design coefficient ‘C' is 1.25.
比如：SDR11的PE100的给水管道的MOP或压力等级是多少？
PE100的MRS=10MPa,给水管道的安全系数C被认为是1.25。
Hence;因此，
MOP = 20 * 10 / 1.25 (11 - 1)
MOP = 16 bar。
