Short Description

Model No.: ASTM-338-Titanium-Coil-Tube

China Titanium Coil Tube Manufacturer supplies ASTM B338 Titanium Coil Tube.

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Key Specifications / Features

Type: Titanium Coil Tube
Material: Grade 1 (UNS R50250), Grade 2 (UNS R50400), Grade 5 (UNS R56400), Grade 7 (UNS R52400),Grade 9 (UNS R56320), Grade 12 (UNS R53400),etc
Standard: ASTM B338
Wall Thickness: 0.5~10mm
Outer Diameter: 6~168mm
Inside Diameter: 10~100mm

Length: Max. 17 meters (specific or random)
Delivery conditions: Annealed, pickled & polished

Titanium coil is mainly used for heating and cooling of containers. Titanium coil is fixed in detachable and non detachable ways, which depends on the medium of materials and the corrosion of titanium coil. However, detachable type is mainly used in the design to facilitate the maintenance and cleaning of titanium coil.
Titanium coil tubes are widely used in heat-exchange equipment, such as tube type heat-exchanger, coiled type heat-exchanger, coil heat-exchanger, condensator, evaporator and transmission pipeline.

Chemical Composition % of Titanium Coil Tube

STANDARD CHEMICAL COMPOSITION (weight %, ma√ or range)
Grade UNS N C H Fe O Al V Pd Mo Ni
GR 1 R50250 0.03 0.08 0.015 0.2 0.18
GR 2 R50400 0.03 0.08 0.015 0.3 0.25
GR 3 R50550 0.05 0.08 0.015 0.3 0.35
GR 4 R50700 0.05 0.08 0.015 0.5 0.4
GR 5 R56400 0.05 0.08 0.015 0.4 0.2 5.5-6.75 3.5-4.5
GR 7 R52400 0.03 0.08 0.015 0.3 0.25 0.12-0.25
GR 9 R56320 0.03 0.08 0.015 0.25 0.15 2.5-3.5  2.0-3.0 
GR 12 R53400 0.03 0.08 0.015 0.3 0.25 0.2-0.4 0.6-0.9
GR 23 R56401 0.03 0.08 0.0125 0.25 0.13 5.5-6.5 3.5-4.5

Mechanical Properties of Titanium Coil Tube

Grade UNS Tensile Yield El. Red.
No Mpa Mpa % %
GR 1 R50250 240 138 24 30
GR 2 R50400 345 275 20 30
GR 3 R50550 450 380 18 30
GR 4 R50700 550 483 15 25
GR 5 R56400 895 828 10 25
GR 7 R52400 345 275 20 30
GR 9 R56320 620 483 15 25
GR 12 R53400 483 345 18 25
GR 23 R56401 828 759 10 15

China Titanium Coil Tube Manufacturer supplies ASTM B338 Titanium Coil Tube.

The Manufacturing Process of Titanium Coil Tube

The first step in the typical coil tube manufacturing process involves the acquisition of steel stock supplied in 40- to 48-in.-wide sheets that are wrapped onto a “master coil” to a nominal weight of approximately 40,000 lbm. As a result, the lengths of sheet steel will vary depending upon the wall thickness. For example, a 40-in.-wide sheet of steel having a wall thickness of 0.109 in. rolled to a length of 2,700 ft will weigh approximately 40,000 lbm. If the 40-in.-wide sheet steel has a wall thickness of 0.156 in., a 40,000 lbm-master coil will have a length of approximately 1,900 ft.

When the diameter of the coil tube is selected, the sheet steel on the master coil is “slit” into a continuous strip of a specific width to form the circumference of the specified tube. The flat skelp is then welded to another segment of skelp to form a continuous length of steel. The welded area is dressed off smooth, cleaned, and then x-ray inspected to ensure that the weld is free from defects. Once a sufficient length of the continuous skelp steel is rolled onto the skelp take-up reel, the tube milling process can begin.

The skelp is then run through a series of roller dies that mechanically work the flat steel into the shape of a tube. At a point immediately ahead of the last set of forming rollers, the edges of the tube walls are positioned very close to each other. These edges are then joined together by an electric welding process described as “high-frequency induction” (HFI) welding. The HFI coil generates the heat for welding by the resistance to flow of electric current. As the tube is run through the high-frequency induction coil positioned inches ahead of the forming rollers, the edges of the walls are heated to the temperature needed to create the seam weld when pressed together within the last set of forming rollers.

The weld flash exposed on the outside of the tube is removed, and the welded seam is annealed. The tube is allowed to cool in air and then within a liquid bath before passing through a nondestructive inspection station to inspect the tube body. The inspection is typically performed with an eddy-current device that creates a magnetic field around the tube body and looks for distortions in the field created by surface defects in the tube body.

The manufacturing process continues as the tube is run through a sizing mill that slightly reduces the diameter after welding and works the tubing to the required outside diameter (OD) and roundness tolerances. At this time, the tubing undergoes full-body heat treatment using induction coils. The purpose of the heat treatment is to stress-relieve the entire tube, increasing the ductility of the steel. The tube is allowed to cool, first gradually in air and then within a liquid bath. This process results in the development of pearlite and ferrite grain sizes within the steel microstructure. The final product is a high-strength coil tube string with ductility and physical properties appropriate for the specified yield range. The tube is then spooled onto a steel or wooden take-up reel and subjected to a hydrostatic pressure test using water treated with corrosion inhibitors.

Alternative coil tube manufacturing processes may require that a string be constructed by butt-welding sections of tube together. The tube-to-tube welding technique may be performed using TIG or MIG (Tungsten inert gas or Metal inert gas) welding practices, and each weld should be inspected using radiographic inspection (x-ray) or ultrasonic inspection to evaluate the quality of the weld. Note that the exterior surface of the tube-to-tube weld may or may not be dressed off and that the weld bead on the inside diameter (ID) surface is not disturbed in any way. The string of tubing is then spooled onto the service reel or shipping reel as required.

All manufactured spools of coil tube are given a unique identification number that is assigned at the time of manufacture. Documentation for each spool of coil tube should include:

  • The identification number
  • OD of the tubing
  • Material grade
  • Wall thickness(es)
  • Weld positions
  • Total length

A spool of coil tube may be manufactured from one heat or a combination of heats that are selected according to a documented procedure provided by the manufacturer. However, the steel used to fabricate the string must have a uniform material yield strength throughout. The manufacturer should maintain traceability of the coil tube product throughout the manufacturing and testing process. The requirements of the purchaser often include traceability to the heat of steel.

Tapered wall thickness string design

In general, tapered coil tube strings can be manufactured by changing the wall thickness of the tubing within the length of a spool while maintaining a constant OD. The changes in wall thickness along the string length are intended to increase the performance properties of the coil tube in the selected sections. The construction of a tapered coil tube string may be achieved in one of the following ways:

  • A continuously milled string incorporating multiple single-wall-thickness skelp segments joined using skelp-end welds.
  • A continuously milled string incorporating single-wall-thickness skelp segments with continuously tapered skelp segments joined using skelp-end welds.
  • Continuously milled, single-wall-thickness coil tube segments joined to another finished tube segment of a different wall thickness using the tube-to-tube welding process.

Continuously-tapered skelp is milled having a specified wall thickness at the leading end of the steel skelp, progressively increasing in wall thickness along the length of the skelp to a second specified wall thickness at the trailing end of the skelp.

The construction of tapered coil tube strings conforms to the previously described manufacturing processes. Although tube segments of different wall thickness can be assembled within the string construction, it is critical that all of the segments have a uniform material yield strength . The change in specified wall thickness, t, between the adjoining coil tube segments should not exceed the following specified values:

  • 0.008 in. where the specified wall thickness of the thicker of the adjoining segments is less than 0.110 in.
  • 0.020 in. where the specified wall thickness of the thicker of the adjoining segments is between 0.110 and 0.223 in.
  • 0.031 in. where the specified wall thickness of the thicker of the adjoining segments is 0.224 in. and greater.

Tapered coiled tubing can increase the operating depths and pressures where coil tube is applicable.

Transition points

String Type Transition Point Defined As:
Tapered-wall string designs The points along the string having a change in the specified wall thickness
Single-wall-thickness segments The points where the different specified wall thicknesses are mechanically joined together
Continuously tapered skelp segments The points where the ramping of the skelp occurs

The typical design criteria for selecting transition points (desired lengths of specified-wall thickness segments) within the string includes weight and overpull loading, wellbore condition, and combined pressure loading. Note that the overpull load rating increases for the adjoining tube segment with an increased wall thickness. The effect of changes in overpull load should be applied across the entire tapered string to ensure that a given overpull load does not exceed the limits of any other tube segment within the string. Therefore, the maximum length of each coil tube wall thickness segment should be evaluated using overpull and combined pressure loading to confirm that the stress applied to the coil tube string below any point on the segment does not exceed the triaxial stress load at that point for the given safety factor.

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