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SDR versus DR

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  • SDR versus DR

    For a number of years I have worked on pipe crews as an operator. Last winter I started to learn directional drilling. I noticed that some pipe is labeled SDR and some DR. Does anyone know what the different designations signify?


  • #2
    Re: SDR versus DR

    If I remember correctly,it has to do with the outside diameter of the pipe,SDR stands for Standard Dimension Ratio.While DR is not standard thickness,basically same pipe, but do not quote me on this


    • #3
      Re: SDR versus DR

      check out these quotes form the links, this is what I found in a net search,

      SDR, DR, Schedule or wall thickness
      The standard dimension ratio (SDR), dimensional ratio (DR), schedule or wall thickness. The SDR or DR is the pipe OD divided by pipe wall. The schedule number of the pipe is an alternate identifier. These numbers can be found on the print line or in the case of DR and SDR, by measuring the wall thickness and dividing it into the pipes outside diameter. The wall thickness is the measurement in inches between the inside and outside wall of the plastic pipe. It may be found on the print line or measured using a caliper.

      a more detailed explanation, but basicly the same as the bottom quote.
      The bottom line is simple: the two terms
      are interchangeable. SDR=DR=OD/t.
      Q: What is the difference between DR and SDR?
      A: The terms “dimension ratio” and “standard dimension ratio” are widely used in the PVC pipe industry. Both terms refer to the same ratio, which is a dimensionless term that is obtained by dividing the average outside diameter of the pipe by the minimum pipe wall thickness.

      Dimension ratios and standard dimension ratios were developed out of convenience rather than out of necessity. They have been established to simplify standardization in the specification of plastic pipe on an international basis. Since these define a constant ratio between outer diameter and wall thickness, they provide a simple means of specifying product dimensions to maintain constant mechanical properties regardless of pipe size. In other words, for a given DR or SDR, pressure capacity and pipe stiffness remain constant regardless of pipe size.

      Even though the terms DR and SDR are synonymous, one minor difference between them is that SDR refers only to a particular series of numbers, i.e., 51, 41, 32.5, 26, 21, etc. This series of “preferred numbers” is based on a geometric progression, and was developed by a French engineer named Charles Renard. These numbers are often called “Renard’s Numbers.”

      The term DR became widely used, in 1975, with the publication of AWWA C900, which governs production of small diameter PVC pressure pipe. AWWA allowed the desired pressure capacity to dictate wall thickness. Since the OD/t values generated did not happen to fall on any of Renard’s Numbers, AWWA removed the “standard” designation from the SDR term.

      It is interesting to note that the most widely used product for small diameter sanitary sewer in the U.S., ASTM D 3034, SDR 35, provides an apparent contradiction in terms. While 35 is not a Renard Number, it is still referred to as a standard dimension ratio. In fact, all OD/t ratios in D3034 are listed as SDRs whether they are included in Renard’s “preferred numbers” or not. This was probably for convenience’ sake. D3034 was written in 1972, prior to the popularization of the DR term. Accordingly, ASTM may have allowed all OD/t ratios to be called SDRs.

      The bottom line is simple: the two terms are interchangeable. SDR=DR=OD/t.
      SDR or DR or Schedule XX:
      PVC pipe may be classified as SDR or DR or Schedule XX.

      SDR and DR are essentially the same thing (Standard Dimension Ratio). Both are the average outside diameter divided by the minimum wall thickness. A French engineer came up with a series of preferred numbers and these are the "Standards" (thus, SDR). Many others have since been developed and are frequently referred to as DR. Some references use the "S" on all. It really doesn't make the least bit of difference. I'll use SDR from here out to refer to both.

      Since SDR is a diameter to thickness ratio, all pipes with the same SDR have the same pressure rating.

      Schedule 40 pipes all have the same wall thickness. Schedule 80 pipes all have the same. Thus, all pipes that are Schedule 40 do not have the same pressure rating. Same for Schedule 80. There's also Schedule 120.

      just a lot of information on the below link
      Last edited by BHD; 04-21-2007, 02:22 PM. Reason: typo
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