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' Some of the joints tested had comments included on the results page that <br />mentioned a variation in pipe wall thickness. The joint with the most comments <br />' was joint #52. The pipe wall thickness was found to vary between 2.090 inches <br />and 1.800 inches around the circumference of the pipe. The minimum wall <br />' thickness for 24-inch SDR 13.5 pipe is 1.778 inches. The minimum thickness <br />measured is therefore greater than the minimum thickness allowed for this size of <br />' pipe, and the variation is therefore acceptable. Joint # 48 also had a minimum wall <br />thickness of 1.800 inches, which is again greater than the 1 .778 inches required. <br />' Joint #52 also has the comment on pipe wall mismatch around the perimeter <br />' of the pipe. Since the pipe is made from plastic, there is often a variation from <br />perfect roundness due to the pipe laying on the ground, etc. Depending on the way <br />the two sections are aligned', sometimes the "ovality" of the pipes is mismatched, <br />resulting in an offset of the wall. This mismatch is cha.cked for when the joints are <br />' tested-fitted together before the actual welding process. Some misalignment is <br />allowed by the manufacturer, up to a maximum of 10% of the wall thickness, or in <br />this case, a maximum of 0.18 inch. The report mentions a misalignment of 0.25 <br />inch, which at first glance seems to be greater than allowed. However, the wall <br />thickness at this area was also measured at 2.090 inches. If 0.25 inch is <br />' subtracted from a wall thickness of 2.090 inches, the remaining thickness is 1.840 <br />inches. Therefore, even with a 0.25-inch mismatch, the wall material fused is still <br />' thicker than the minimum pipe wall thickness. This joint should therefore be <br />acceptable. <br />The report also has some areas where a loss of signal occurs. These areas <br />are where scratches on the pipe surface reduce the contact of the test sensor, <br />reducing or even eliminating the signal. These scratches are the result of the <br />construction process, where several sections of pipe are fused together, and the <br />entire assembly is dragged into place. This is the only practical method for installing <br />long sections of pipeline, and scratches on the pipe surface are often produced. The <br />pipe manufacturer allows the pipe to be used up to its full pressure rating, as long <br />6 <br />