Inspection method of casing & tubing in mill.

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API tubing is inspected at the mill in accordance with API Spec. 5CT. Physical properties are checked and each length hydrostatically tested to required pressure condition.

API tubing is inspected at the mill in accordance with API Spec. 5CT. Physical properties are checked and each length hydrostatically tested to required pressure condition. The following are also checked:
• Dimensions
• Weights
• Straightness
• Lengths
Part of this inspection is to drift all lengths.
Despite all the American Petroleum Institute (API) specifications and testing, some tubing defects are still found after delivery; thus, some operators do further inspection of new tubing on critical wells.

Inspection methods on site
There are several types of tubing inspection methods that may be beneficial. The common methods of inspecting the tubing currently in use in field operation are:
• Visual
• Calipers
• Hydrostatic
• Electromagnetic
• Magnetic particle
• Ultrasonic

Typical defects are outside and inside pits and longitudinal cuts, transverse laps, and mechanical wear and erosion. API recommends that wall thickness measurements be made with pipe wall micrometers, sonic pulse-echo instruments, or gamma ray devices so that the operator can demonstrate the wall thickness within a 2% accuracy. In addition to the body, the tubing upset and threads often require inspection, typically by magnetic powder and use of thread gauges. The following guidelines are suggested for inspection normally at the well location:

• Visual. The outside of each tubing joint should be inspected visually for mill defects such as seams, slugs, pits, cuts, gouges, dents, or cracks. Each connection should be checked for defective threads and seals. Wall thickness measurements should be considered on critical wells. Internal inspection of tubing requires the use of an optical device and an experienced operator. The operating crews, a manufacturer’s representative, the user’s personnel, or a service contractor typically does such visual inspections.

• Calipers. Tubing calipers, both multifingered feeler and electronic types, normally are run while the tubing is installed in the well. Where significant wall loss is observed, the tubing can be pulled and the damaged joints replaced.

• Hydrostatic. A commonly used inspection method is to test hydrostatically the tubing body and joint internally with water. Test pressures are usually based on 80% of internal yield. Hydrostatic tests of the body are performed on the pipe rack on location and the joints checked while running; however, both can be tested while running. A more stringent test of the joints is obtained by the use of nitrogen with a helium tracer rather than water.

• Electromagnetic. To find pits, transverse and/or longitudinal defects in the pipe body, electromagnetic search coils, which find magnetic flux leakage, are typically used. This technique works for a uniform body and will typically not find defects in the upset and/or threaded area of the tube. The inspection equipment must be in good working order and an experienced and qualified operator is required. Eddy-Current, another electromagnetic inspection method, is used for grade verification.

• Magnetic particle. The magnetic particle inspection methods, both wet and dry, induce either a longitudinal or transverse magnetic field in the tubing and magnetic iron particles dusted on the tubing align at defects. This method is normally used to check the outside surface of upset and end area region for cracks. This method requires a qualified operator, excellent operating environmental conditions, and good operating procedures to be reliable.

• Ultrasonic. Ultrasonic test is used to find flaws and imperfections in the pipe body wall. The tool is usually stationary and the pipe is rotated and fed mechanically to examine the entire tubing body. The ultrasonic testing equipment must be in good working condition and an experienced and qualified operator is mandatory.

• Hardness testing. The hardness of tubing is often checked when it is to be used in sour service to ensure the tubing meets API Spec. 5CT or to sort mixed grades of tubing.



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