Recent growth in oil drilling and gas extraction to serve the energy market has increased the demand for Oil Country Tubular Goods (OCTG). At the same time, global product standards pertaining to pipe and tube testing — including ANSI/API Spec 5L, ISO 3183:2012, ISO 6892-1:2009, ASTM A370, and ASTM E8M — are evolving to facilitate global standardization, which creates a challenge for pipe and tube manufacturers. Instron® testing systems are designed to meet these developing challenges of the Pipe and Tube Industry.
So what are the pipe manufacturers’ problems with durability testing?
The first, Specimen Geometry: The curved shape of pipe and tube presents a number of challenges when tensile testing.
- Test specifications permit “end flattening” prior to testing. However, it is time consuming and difficult to achieve with thicker material.
- At the same time, ensuring proper grips is a problem for curved surfaces and allows for the ability to slip samples.
What Solution? Use jaw faces to match the concave portion of the longitudinal strip specimen.
- Incorporates an interchangeable face for the concave portion of the specimen that can be easily equipped with different inserts to test various sizes of pipe and tube
- Uses a standard vee jaw to grip the convex portion of the specimen
- Standard flat jaw sets are available and are suitable for thin-walled material
The second, testing full section pipe/tube
Generally, producers want to test the largest section of pipe, but specimen preparation is time consuming.
- Gripping hollow material will cause crushing
- The grip jaw opening is the limiting factor in determining how large the pipe (or tube) sample can be tested
- A higher capacity system is often required in order to accept larger diameter test specimens
End plugs, which are typically manufactured by the producer, are inserted into each end of the specimen during testing
- Prevents crushing
- Made to size
The third is Impact Testing High-Strength Materials
New materials being used in the pipe and tube industry for higher strength and durability require larger impact energies to perform standard Charpy tests to ASTM E-23 and ISO 148.
- Require larger testing systems
- Demand more versatility from pendulum systems
- May require quick modifications of hammer size
- Increased safety requirements due to specimen debris
The Instron® MPX Series motorized impact testing system in 300-900 Joule capacities with adjustable hammer energy is capable of testing higher strength maraging steels and newer alloys with Niobium or Chromium.
- Interchangeable hammer weights adjust the system capacity without removal of the hammer shaft
- Automatic release of the hammer upon closure of guard door for cold specimen breaks and NIST certification
- Motorized hammer and interlocked guard protects technician from injury
- Easy-to-use software interface
The last is choose suitable strain measurement
The irregular specimen geometry of pipe and tube makes choosing an extensometer difficult. Not all 50 mm (2 in) gage length clip-on style instruments are appropriate.
The Instron® model T3M (W-6204) Clip-on Extensometer
- Can be used to test whole tubes up to 89 mm (3.5 in) in diameter
- Back support securely meets the contour of the inner portion of the longitudinal strip specimen
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