Coiled Tubing

Manufacturing Range

Coiled tubing is available in a range of different product forms depending on the customer requirements. We manufacture seam welded and redrawn, seam welded and floating plug redrawn and seamless tube products. The standard grades are 316L, alloy 825 and alloy 625. Other grades of stainless steel in duplex and superduplex and nickel alloy are available on request. Tubing can be supplied in the annealed or cold worked condition.

• Welded and drawn tubing.
• Diameter from 3mm (0.118”) to 25.4mm (1.00”) OD.
• Wall thickness from 0.5mm (0.020”) to 3mm (0.118”).
• OD tolerance +/- 0.005” (0.13mm) and +/- 10% wall thickness. Other tolerances are available on request.
• Coil lengths up to 1500m (5,000ft) without orbital joints depending on product dimensions.
• Coil lengths up to 13,500m (45,000ft) with orbital joints.
• Encapsulated, PVC coated or bare line tubing.
• Available on wooden or steel spools.

Manufacturing Range

Coiled tubing is available in a range of different product forms depending on the customer requirements. We manufacture seam welded and redrawn, seam welded and floating plug redrawn and seamless tube products. The standard grades are 316L, alloy 825 and alloy 625. Other grades of stainless steel in duplex and superduplex and nickel alloy are available on request. Tubing can be supplied in the annealed or cold worked condition.

• Welded and drawn tubing.

• Diameter from 3mm (0.118”) to 25.4mm (1.00”) OD.

• Wall thickness from 0.5mm (0.020”) to 3mm (0.118”).

• OD tolerance +/- 0.005” (0.13mm) and +/- 10% wall thickness. Other tolerances are available on request.

• Coil lengths up to 1500m (5,000ft) without orbital joints depending on product dimensions.

• Coil lengths up to 13,500m (45,000ft) with orbital joints.

• Encapsulated, PVC coated or bare line tubing.

• Available on wooden or steel spools.

Applications

MEILONG offers coiled control line in stainless steel and nickel alloys.

Our products are used in the following applications:

• Downhole hydraulic control lines.

• Downhole chemical control lines.

• Subsea control lines for hydraulic power and chemical injection.

• Smoothbore control lines used in fibre optic applications.

Quality Considerations

When specifying the type of tubing for a particular environment several factors should be taken into account. The most important criteria influencing this decision will be pressure capability and risk of corrosion. A seamless tube that has been cold worked and annealed has a completely homogeneous crystalline wrought structure. The strip material used to make a welded tube is of the same form but this becomes a cast structure at the weld, which could corrode preferentially to the surrounding tube. Through the combination of cold work and subsequent annealing the weld metal can be re-crystallised, transforming this area to a wrought structure resulting in a homogeneous cross-section with equal corrosion potential all around the tube similar to a seamless tube. Sinking goes a long way to achieving this recrystallisation of the cast weld structure into a partially homogenised annealed structure. The extra work in the weld area imparted by passes of drawing processes ensure full re-crystallisation.

In theory the pressure capability of tubing made by the welded and annealed method should be the same but it is common practice in design codes to down-rate welded tubing due to the risk of an imperfect weld leading to weakness. The strains involved in a following redrawing operation will establish the quality of the seam weld and any centre-line weakness will be exposed and detected by visual inspection and/or pressure testing. Therefore the seamless welded and sunk and welded & sunk/plug drawn tubes have the same pressure rating which is superior to that of welded tubing.

Other considerations that can affect the type of tubing specified are surface roughness, compatibility with compression fittings, tolerances, concentricity, length and, of course, price. Welded tubing has a smooth OD & ID finish except for the bead, which can be pronounced in the weld area. This can cause problems with compression fittings. Welded & sunk tubing has a smooth OD surface making it suitable for use with compression fittings but a somewhat rougher bore condition due to sinking and a pronounced weld bead on the ID only. Welded & plug drawn and seamless tubes have a smooth OD surface together with a uniform bore surface with no protruding weld bead.

Tubes made by welding from strip are generally more concentric than seamless tubes, where the uniformity of wall thickness is dependent on the concentricity of the first piercing into hollow form. However, seamless tubes will meet standard commercial tolerances such as those in ASTM A269.

Generally longer lengths can be made by seam welding from strip than can be obtained by drawing down from seamless hollows. These lengths can be further extended by sinking or plug drawing. Where very long lengths are required individual coils can be butt welded together using autogeneous orbital welding, each weld being radiographically examined to ensure that it is free of defects and the complete line is then subject to a pressure test. Welded and redrawn type tubing will need far fewer joints than a seamless line of the same overall length, which leads to significant cost savings.

Advantages of Redrawing Welded Tube

Long lengths can be made by seam welding formed strip but such tubing has OD & ID discontinuity and may suffer from local problems of mechanical strength or corrosion. A welded & sunk tube improves these aspects and has been proven reliable in service over several decades for offshore applications. Although more expensive than welded only tubing, the welded and redrawn tube is still relatively inexpensive compared to Seamless.

Seamless tubing has cross sectional uniformity however, it is the most expensive method of manufacture and has a limitation in the continuous length that can be produced between joints. For a slight premium over the welded & sunk price, tubing can be produced by the welded & floating plug drawn process which results in a product of similar appearance to seamless but with the significant advantage of much longer continuous lengths and greatly reduced costs.

Quality Assurance

Process and quality control of MEILONG TUBE products is critical in respect of consistently achieving the highest standards in critical Oil & Gas applications. Strict quality control is applied at every stage of the processing operations. Individual quality plans tailored to the customers’ project requirements can also be incorporated into our product quality.

The control line is 100% dimensionally inspected and eddy current tested to international ASTM or DIN standards. All lines are 100% hydraulically pressure tested before being released and certified. Any orbital joints are also radiographically tested in a minimum of 3 planes to ensure the quality of the joint.

We have BS EN ISO 9001 and BS EN ISO 14001 approvals as well as individual client approvals.

Control Line Pressure

The working pressure for a tube depends on the operating conditions of each particular application and the factor of safety required. This can be determined only by the customer and is expressed as a proportion of either the yield pressure or the nominal burst pressure of the tubing. These are the values that raise the stress to the theoretical yield point or the ultimate tensile strength for the material.

Safe working pressures have traditionally been expressed as a proportion of either the tensile strength or yield point of a tube. Different industries and pressure vessel codes have adopted different practices.

Quality assurance

The quality of our products for the control line in oil and gas sector is assured not just during the controlled manufacturing process but also by way of finished product testing. Typical tests include:

• Non-destructive tests

• Hydrostatic tests

• Surface finish controls

• Dimensional accuracy measurements

• Flare and coning tests

• Mechanical and chemical property testing

Conventional sizes

1/8’’ x 0.028’’

1/8’’ x 0.035’’

3/16’’ x 0.028’’

3/16’’ x 0.035’’

3/16’’ x 0.049’’

1/4’’ x 0.035’’

1/4’’ x 0.049’’

1/4’’ x 0.065’’

1/4’’ x 0.083’’

3/8’’ x 0.035’’

3/8’’ x 0.049’’

3/8’’ x 0.065’’

3/8’’ x 0.083’’

1/2’’ x 0.035’’

1/2’’ x 0.049’’

1/2’’ x 0.065’’

1/2’’ x 0.083’’