Drift Mandrel Size, in.
Product and Size, in.
Casing and Liners 8-Vh and smaller 9Vs to 13-Vs, inclusive 16 and larger
6 12 12
27/h and smaller 3>/2 and larger
Courtesy American Petroleum Institute wall thickness, t, of the pipe body has a -12.5% tolerance. The thickness tolerance is used in burst calculations.
API Spec. 5A addresses pipe eccentricity. The maximum eccentricity of the OD, measured with a saddle gauge at a distance of 5-6 in. from the end of the upset, may not exceed 0.093 in. The eccentricity constraints on the bore of the upset with respect to the outside surface of the drillpipe may noi be more than '/ift in. ('/s in. total indicator reading). Maximum ovality, measured with a micrometer on the OD of the upscl, may not exceed 0.093 in.*
The drift diameter of the casing relates to the diameter of a mandrel thai can pass through the easing bore without exerting unreasonable forces. The drift diameter is smaller than the ID due to eccentricity and nonstraight bore tolerances. For drilling considerations, the drift diameter is usually considered as the bit size that can be safely run through the casing. It is common practice to drift test the casing before it leaves the mill and immediately before running ii into the well.
Bach length of casing and lubing must be tested throughout iis entire length with a cylindrical drift mandrel conforming to the following requirements if the casing is to carry the API monogram (see Table 11-4). The leading edge of the drift mandrel must be rounded to permit easy entry into the pipe. It must pass freely through the pipe with a reasonable exerted force equivalent to the weight of the mandrel being used for the test. Pipe cannot be rejected until it has been drift tested when it is free of all foreign matter and properly supported lo prevent sagging.
Burst. The burst rating of the casing is the amount of internal pressure that the pipe can withstand prior to failure. The internal yield pressure for pipe
*API Specification 5A, is calculated from Eq, 11.3. The factor of 0,875 accounts for minimum wall thickness,
Pf! = burst pressure rounded to the nearest SO psi Y,, = specified minimum yield strength, psi t = nominal wall thickness, in. OD = nominal outside diameter, in.
Example 11.1 illustrates use of Eq. 11,3.
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