HYDRAULIC CONTROL AND INSTRUMENTATION APPLICATIONS

STAINLESS STEEL AND HIGH NICKEL ALLOYS COILED TUBING SOLUTIONS

MEILONG is an important manufacturer in premium coiled seamless & welded tubular solutions for oil and gas applications. In an endeavor to increase its presence in subsea, MEILONG has extended its offer by developing a highly innovative tubular solution for umbilical projects.

MEILONG has developed a strong and unique expertise in premium quality tubes to answer the most stringent specifications of its customers. Based on this expertise in high pressure, and extremely high pressure tubes, MEILONG’s state-of-art factory is exclusively dedicated to the manufacturing and supply of super duplex and high nickel alloys tubes for corrosive downhole applications and is now ready to offer the highest specifications for your toughest challenges.

Description

TP316L is a chromium-nickel austenitic stainless steel with an addition of molybdenum and reduced carbon content. The addition of molybdenum provides improved resistance to pitting and crevice corrosion in environments containing halides such as chlorides when compared to so-called conventional 18 chromium 8 nickel austenitic stainless steels such as 304L. The reduced carbon content minimizes harmful chromium carbide precipitation during welding and thereby improves resistance to intergranular corrosion. Austenitic stainless steels such as TP316L are susceptible to stress corrosion cracking (SCC) in environments containing chlorides and other halides. ANSI 316L is generally used in oil and gas production environments which do not contain oxygen and have limited amounts of chlorides and hydrogen sulfide. Consult ISO 15156-3, Table A.2 for the limits regarding TP316L in hydrogen sulfide-containing environments for oil and gas production.

Corrosion Resistance

● Organic acids at high concentrations and moderate temperatures

● Inorganic acids, e.g. phosphoric and sulphuric acids, at moderate concentrations and temperatures. The steel can also be used in sulphuric acid of concentrations above 90% at low temperature.

● Salt solutions, e.g. sulphates, sulphides and sulphites

● Caustic environments

Austenitic steels are susceptible to stress corrosion cracking. This may occur at temperatures above about 60°C (140°F) if the steel is subjected to tensile stresses and at the same time comes into contact with certain solutions, particularly those containing chlorides. Such service conditions should therefore be avoided. Conditions when plants are shut down must also be considered, as the condensates which are then formed can develop conditions that lead to both stress corrosion cracking and pitting.

TP316L has a low carbon content and therefore better resistance to intergranular corrosion than steels of type TP316.

Application (seamless tubing)

TP316L seamless pressure tubing in the heat treated condition is typically used in oil and natural gas wells for applications including hydraulically-actuated surface-controlled subsurface safety valves, chemical injection, and instrumentation. In such applications, it is commonly referred to as control line tubing. The tubing is generally deployed by strapping it to the outside of the production casing. It may be encapsulated and can be included along with other pressure or TEC and mechanical components, such as bumpers, within a flatpack. The tubing is frequently supplied as 5,000 to 35,000 ft. coils on a wooden or steel reel, depending on size.

TP316L, Chemical composition

Application: Standard oil and gas CRA (corrosion resistant alloy)

Tensile strength, min.: 70ksi (485MPa)

Yield strength, min.: 25ksi (170MPa)

Elongation in 2 in., min.: 35%

Capillary String Size

Tubing length up to 32,808 feet (10,000 m)

For control line, chemical injection line, umbilicals

Dimensional tolerances: ASTM A632 standard is used to define permissible variation in tubing wall thickness and diameter.

Variation in tubing diameter:

+0.003’’ is permissible for tubing below 0.188’’ diameter and

+0.004’’ is for tubing above 0.188’’ nominal diameter

Variation in wall thickness: For both seamless and welded tubing +10/-10% deviation is acceptable

No negative tolerance permitted on the variation on length measurement

Orbital welds: Each one reel of tubing is a continuous length without orbital butt welds

Pressure rating: The pressure rating shall be specified on the PO.

Material quality: The material shall be free of injurious seams, laps, longitudinal and transverse notches or other imperfections, which due to their nature will interfere with the use of the material I final usage of the part.

Pressure testing: Each coil of tubing shall be hydrostatically pressure tested at its maximum rated test pressure (specified in purchase order or the supplied test pressure rating table) for a minimum of 15 minutes. The test pressure of the tubing shall be reported on the certification.

Production Process

Welded & Redrawn Tubing

Strip splice welds join lengths of cold rolled strip to enable long lengths between orbital welds (greater than 14,500 ft between orbital welds is achievable). The strip is formed into a tubular cross section and longitudinally seam welded using the gas tungsten arc (GTAW) process. The tubing is first sunk to an intermediate outside diameter, heat treated, and make the same process to obtain the desired size.

Seamless & Redrawn Tubing

Seamless extruded tube hollows are drawn or drawn / sunk to final size to produce seamless tubing coils 500 to 2,000 ft. long, depending upon the size. The tubing is heat treated and joined by orbital welding to achieve the desired length. The final material condition of the tubing is heat treated.

Standards and Specifications

ASTM A269, Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General Service

Meets the material limits for 316L austenitic stainless steel listed in ISO 15156-3, Table A.2.

Tube markings include size, material type/grade, specification, heat number, and other information.

Quality Assurance

Eddy current test (ECT)

Ultrasonic test

Hydrostatic test

Chemical composition analysis

Tensile test

Hardness test

Dimension & visual inspect

Metallographic analysis

Duplex Stainless 2205, Characteristics and properties

Available Material Grades