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Dimensional Testing (ASTM D 2122):

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Why is Dimensional Testing Important?

There are several reasons that dimensional testing is performed. First, when solvent cement joints are made, the strength and integrity of the bond is dependent on there being a proper interference fit between the pipe and the socket, and that neither the pipe nor the fitting be too oval.

Second, in order to maintain and the hold the internal pressure, a certain wall thickness is necessary. Finally, For some fittings, certain lengths, called ‘laying lengths’ are standardized to make calculating runs of pipe easier; these lengths must be verified.

What is the difference between Tolerance and Out-of-Roundness?

When measuring the diameter of a pipe or socket, the diameter is calculated by taking the average of eight measurements spaced equidistantly around the specimen. The average must fall within a certain range called the Tolerance. The individual measurements, however, may fall above or below this range, indicating that the specimen is not round, but rather oval or egg-shaped.

How much is acceptable?

That is the purpose of Out-of-Roundness, or Ovality. While there have been several methods of calculating this in the past, the method currently specified in ASTM D 2122 is the difference between the largest and smallest diameter measurements.

1.1 The Dimensional Test method covers the determination of diameter, wall thickness, and length dimensions of thermoplastic pipe. Included in the Dimensional Test are procedures for measurement of the inside diameter of pipe intended to be joined by internal fittings, measurement of the average outside diameter for roundable pipe where out-of-roundness is not of primary concern, out-of-roundness measurement and measurement of the average outside diameter of non-roundable pipe, !md for determining length and straightness.
1.2 The Dimensional Test method also includes procedures for dimensioning molded thermoplastic pipe fittings.
1.3 The Dimensional Test values given in parentheses are provided for information purposes only.
1.4 The Dimensional Test standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determining the applicability of regulatory limitations prior to use.

Should you need additional information about CRT Laboratories' Dimensional Compliance testing capabilities please contact us via our RFQ Form or call us at (714) 283-2032. You may fax a request for a proposal at (714) 283-1365.