Oil Casing Processing Technology and Manufacturing Process

Oil Casing Processing Technology and Manufacturing Process

1.1 Oil Casing Manufacturing Process

Refer to Figure 1 for the flowchart of the oil casing manufacturing process.

1. Exterior Inspection of Tube Billets
   • There are two sources for the raw materials of casing tube billets: seamless tube billets and ERW (Electric Resistance Welded) tube billets. Both types should be inspected as follows:
     • Check if the entire tube body is smooth and clean, free from obvious dents, wrinkles, indentations, etc.
     • If ERW tube, check if the internal and external burrs of the weld seam have been removed according to regulations and if the weld bead is smooth.
     • Inspect the condition of the tube ends for dents, layers of burrs, smoothness of the flat end chamfering, and whether the chamfer meets regulations. If ERW tube, check for weld seam cracks at the ends.
     • Measure the inner and outer diameters, wall thickness uniformity, bevel angle, ovality, straightness of the steel tube to determine if the precision meets specifications.
     • Check for obvious dirt on the inner and outer surfaces of the tube.

   If the steel tube has any of these issues, it will be transferred to another process for further repair. If defects cannot be repaired, the tube will be classified as scrap and disposed of accordingly.

2. Rust Removal
   • Before entering the production line, the surface rust of the tube body should be removed using a rust removal machine to prevent the tube body from being unable to undergo painting after threading. The result should ensure that the entire tube body is free from rust stains or dirt.

   If rust removal is not possible, the tube body should not proceed to the next step but instead be transferred to another process for further grinding. If the rust has penetrated too deeply into the body to be repaired, the steel tube will be classified as scrap and disposed of accordingly.

3. Full Body Flaw Detection of Tube Billets
   • Primarily inspect for cracks and non-metallic inclusions in the base material of the tube billet. This process must strictly comply with API 5CT standards. This step is automatically detected by eddy current flaw detection equipment. When the equipment alarms, mark the defect promptly and classify the defective tube as scrap for disposal.
4. Threading of Tube Body
   • Alignment:
     • Alignment typically uses the outer diameter as the reference point. Alignment must be done carefully to minimize errors. If the tube is elliptical, alignment should ensure that the error between opposite diagonal points on the tube body is less than 0.3 mm. At least four sets of diagonal alignments are required.
     • Follow the operating procedures to clamp the tube material. Ensure that clamping points are as far away as possible from the area needing threading to avoid deformation due to force. For tubes with noticeably elliptical outer diameters, take special precautions during clamping (such as adding copper strips) to prevent dimensional rebound upon release. Additionally, control the clamping force to avoid deforming the tube due to excessive pressure, leading to scrap.
   • Threading:
     • Threading must be performed on specialized pipe threading machines. Pay attention to the machine’s operation status, adjusting the machine if there are issues with its precision before starting work.
     • After receiving the drawing and task instructions, carefully check the outer and inner diameters, wall thickness, length, and grade markings of the tube body to ensure they meet API standards and drawing requirements.
     • Carefully read the drawings and technical requirements, preparing appropriate tools and cutters.
     • According to the process card accompanying the drawings, process the end face, taper, and threading.
     • Select suitable tools and cutting parameters when threading to ensure the accuracy and surface finish of the thread. Explore the optimal tool life without compromising thread quality solely to save tools.
     • Control the number of passes and cutting depth during processing, ensuring that all steps prioritize the dimensions and quality of the thread.
5. Coupling Tightening
   • Before joining the tube and coupling, apply clean thread compound to the entire surface of the internal and external threads. Brushes or tools used for applying thread compound should be clean and free from foreign matter. The thread compound should not be diluted.
   • When assembling finished and inspected casings with couplings, ensure proper alignment and start turning slowly to ensure normal engagement of the threads.
   • Torque to the specified value and record the details.
   • Apply clean thread protectors to the ends of the casing to prevent thread damage when the tubes roll on racks.
6. Pipe End Passageway Inspection
   • All passageway tests should be performed using required round passageway gauges.
   • The front end of the passageway gauge should be smoothly chamfered to ensure easy passage through the tube.
   • Whether using manual or mechanical methods, the passageway gauge should freely pass through the tube. In case of disputes, use the manual method.
   • During passageway inspection, the inside of the tube should be free from any foreign matter and appropriately supported to prevent sagging or bending.
7. Hydrostatic Pressure Test
   • Clean the inner surface of the tube with a high-pressure water gun.
   • Lubricate the thread surfaces to minimize damage during the hydrostatic test (when installing and removing plugs).
   • Correctly clamp the workpiece and inspect the equipment to ensure all parts are functioning normally.
   • Check the safety and reliability of protective devices.
   • Fill with water and pressurize for 7 seconds.
   • Carefully fill out the “Hydrostatic Test Report for Threaded Casing” according to the workpiece number.
8. Blow Dry
   • Immediately after performing the pipe end passageway test, blow dry the interior of the tube and the threads using compressed air to remove any residual water. Residual water on the threads can also be wiped manually.
9. Length Measurement and Weighting
   • Steel tubes are conveyed via chain conveyors and walking beams to the measurement and weighing equipment positions, where they are sequentially measured and weighed.
     • If the tube is fitted with a coupling, the length should be measured to the outside face of the coupling. If not, make appropriate corrections to include the length of the coupling.
     • Tubes can be weighed in plain-end, thickened-end, threaded, or threaded and coupled forms.
     • Near the threads, mark the name or trademark of the threading plant, specification markings, and thread size and type.
     • Mark the hydrostatic test pressure on the tube body.
10. Painting and Printing
    • Paint the tube bodies of qualified products. Scrap products are diverted to the scrap roller conveyor through the sorter. Use water-soluble transparent paint. Connect data to print online, spraying the measured length, weight data along with the dimensions, grade, standard number, plant logo, etc., onto the surface of the steel tube. Print no more than 150 alphanumeric characters.
11. Apply Thread Compound and Thread Protectors
    • Apply thread compound to the internal and external thread surfaces.
    • Screw on the thread protectors. External thread protectors should cover the full length of the threads, and internal thread protectors should cover the same length as the internal threads.
12. Color Ring Application
    • Apply an exterior coating to the tubes and couplings to prevent rust during transportation.
    • Apply color rings.
13. Final Inspection
    • Visually inspect the surface of each tube for defects.
      • Workshop inspectors should inspect assembled casings, ensuring that the maximum position of the coupling face does not exceed the apex of the triangular marking.
      • Both ends of the casing should have thread compound applied and be fitted with thread protectors.
      • Markings on the casing and coupling should be complete and conform to standards and drawings.
14. Storage
    • Storage Site Requirements:
      • Warehouse keepers should establish detailed records for incoming casings, ensuring records match the physical inventory.
      • The site should have a concrete floor that is clean, flat, free of standing water, and weeds.
      • There should be no corrosive substances such as acids, alkalis, or salts near the storage area.
      • The top of the storage racks should be 50 cm off the ground, with at least three supports per rack, placed on the same level with firm corners.
      • When handling finished casings, operate steadily to avoid collisions.
    • Palletizing Requirements:
      • Casings should be stacked separately according to corrosion conditions and fitted with thread protectors.
      • Each layer of stacked casings should have at least three evenly spaced spacers between them, perpendicular to the tubes and positioned directly above the rack supports.
        • Spacer Specifications:
          • Wood Spacers: 60 mm × 100 mm
          • Metal Bars: 60 mm × 100 mm
      • Each layer of casings should be offset by the length of one coupling towards the external threads.
      • Do not exceed five layers in stacking.
      • Secure both sides of each layer of casings firmly.