Pipe Inspection – Heat Treatment, NDT, Hydrotesting and Marking

Learn about Pipe Inspection – Heat Treatment, NDT, Hydrotesting, and Marking.

In this video, you will learn about various testing and inspection performed during and after the pipe manufacturing to ensure the pipe’s quality before it is dispatched to the site for use. You will learn about Heat Treatment, Non-Destructive Testing, Destructive Testing, Metallurgical Testing, Hydrostatic tests, Visual & Dimension Inspection, and Marking. I highly recommend you watch my other video about the pipe manufacturing process to have a complete understanding. links are given in the description.

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Heat treatment of pipe

Heat treatment of pipe depends on the way it is manufactured.

In the case of a hot finished Pipe, no heat treatment is required. During the manufacturing, Pipe Temp. remain in the range of heat treatment temperature until the final size and thickness are achieved

Whereas in the case of Cold Finished Pipe, Heat treatment is required as per applicable ASTM standards. As the pipe is either cold drawn or temperature is not maintained in the hot finish range.

The selection of heat treatment methods will depend on the types of material and on what material properties you want to restore or further enhance on existing properties. 

These heat treatment methods are Normalizing, Quenching, Tempering, Solution Annealing, Stress-relieving, or it is a combination of these.

Non-Destructive Testing

Non-Destructive Testing is carried out on the piping components to ensure the soundness of the body & weld. NDT will check whether any physical subsurface defects such as crack, porosity, or lack of fusion are present; these defects may affect the performance of components during the service. The most common methods of NDT used are Flux leakage examination or Magnetic flaw detection, Eddy current, Ultrasonic testing, Radiography (Only for Weld), Magnetic particle test of pipe ends & weld seam, And Positive Material Identification.

Ultrasonic testing can be done on full body or only for weld seam, whereas radiography is performed on weld seam only. A magnetic particle test is performed on pipe ends & weld seam. A hardness check is also performed on metal to confirm the standard requirements.

In the future video, I will try to cover a brief overview of these NDT methods so that you have a working-level understanding of these NDT methods. If you are an inspection engineer, you need to know all these testing in much detail. 

Destructive Testing

Destructive tests confirm the mechanical requirements of the manufactured pipe.

In Destructive Testing- a sample from the actual material is cut to perform various tests.

The tensile test is done to check the yield and ultimate tensile of the material. If required by the purchaser or by standard, the high or low-temperature tensile test is also performed.

Bend tests or Guided bend tests are used to check the integrity of the weld joint.

The flattening test examines the ability of plastic deformation in a pipe

Impact test / Charpy V-Notch Test, check the ability of a material to withstand low-temperature conditions

A creep test is performed to check the long-term effect of continued temperature under constant load on steel.

Metallurgical Testing

Metallurgical Tests confirm the chemical requirements of material grades as per the applicable material standard.

Metallurgical Tests are normally known as Micro and Macro testing

Micro Analysis or Chemical Analysis of Raw material, Product, and Weld ensures that all the alloying elements are within the range as specified in the material standard.

Macro Analysis for Weld will check the proper fusion of weld material with pipe material.

Some Special tests are also carried out on the material when it is going to be used in aggressive environments. These tests will ensure that pipe material can withstand such aggressive environments also. Some of the tests are Grain size (AS & SS), IGC- Intergranular Corrosion Test(SS), Ferrite (SS), HIC- Hydrogen-induced Cracking, SSC- Sulfide Stress Corrosion Cracking; these tests are performed when it is asked by the purchaser in his specification.

Hydrostatic Test

A Hydrostatic Test of a pipe is carried out to ensure that the pipe is 100% leakproof. It also ensures the ability of the pipe to withstand pressure.

Hydro test pressure is calculated based on the equation given in ASTM A530; this equation is based on three parameters Pipe OD, Pipe Thickness, and Pipe Wall Stress.

Holding time for the hydro test is a minimum of 5 secs as per ASTM A530. The pressure is monitored by the computerized system.

For welded pipe, the test pressure should be held for a time sufficient to permit the inspector to examine the entire length of the weld seam. 

The hydrostatic test can be waived under certain conditions as set in the standard.

Visual Inspection

Visual Inspection is one of the most effective inspection methods used to check overall product quality. During the visual inspection, you will check for the overall product finish. You will check for surface imperfections such as mechanical marks, lamination, tears, or any other visual imperfections and also check weld defects such as porosity, undercuts, uneven weld bead, and excess or underfill of weld material. Acceptance of these imperfections is as per applicable standards. 

Dimension Inspection & Marking of Pipe

Dimension inspection of the pipe is carried out based on the Dimension Standard. The pipe’s final dimension must confirm the standard, or it should be as specified in the purchaser’s specification.

For Welded and Seamless Wrought Steel Pipe, dimensional requirements are covered in ASME B36.10.

For Stainless Steel Pipe, dimensional requirements are covered in ASME B36.19

During the dimensional inspection, Diameter, Length, Thickness, Straightness, Ovality & Weight are checked. Permissible Variations depend on manufacturing standards. You can visit my website hardhatengineer.com to learn about acceptable tolerances in the pipe dimension.

Once the pipe is cleared for all tests and inspection, it is marked as per the standard requirements. Pipe shall be marked with the Manufacturer logo, ASTM material code, Material Grade, Size, Thickness- schedule no., Length, Heat No, and Special marking WR for weld repair or NH for non-hydro tested pipe.

These Marking can be done with paint or by Hard punching. For stainless steel pipe, stenciling is also used.

Please note that for carbon steel, no hard-punching is below 6 mm thickness, and for stainless steel, no hard-punching is below 12 mm thickness.

This is all about testing, inspection, and marking the pipe.

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