ASTM E426 PDF

A new Edition has just been released and is available now from Document Center Inc. This standard covers the process of using eddy current examination to evaluate tubular products made of low conductivity materials. The materials will be titamium, stainless steel, and other similar alloys like those including nickel. The standard also includes austenitic chromium-nickel stainless steels.

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Electromagnetic Eddy-Current Examination of Seamless and Welded Tubular Products, Titanium, Austenitic Stainless Steel and Similar Alloys1 This standard is issued under the fixed designation E; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision.

A number in parentheses indicates the year of last reapproval. A superscript epsilon indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the U. Department of Defense. Austenitic chromium-nickel stainless steels, which are generally considered to be nonmagnetic, are specifically covered as distinguished from the martensitic and ferritic straight chromium stainless steels which are magnetic.

Coils and probes are available that can be used inside the tubular product; however, their use is not specifically covered in this document. This type of examination is usually employed only to examine tubing which has been installed such as in a heat exchanger. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.

One of these techniques employs one or more exciter and sensor coils which encircle the pipe or tube and through which the tubular product to be examined is passed. Some circuit configurations employ separate exciter and sensor coils; whereas other configurations employ one or more coils that concurrently function as both exciters and 1. Box , Arlingate Ln. AIA , Wilson Blvd. Current edition approved Aug.

Published September Originally approved in Last previous edition approved in as E 98 DOI: United States E 12 5. Significance and Use 5. Changes in electromagnetic response caused by the presence of discontinuities are detected by the sensor, amplified and modified in order to actuate audio or visual indicating devices, or both, or a mechanical marker. Signals can be caused by outer surface, inner surface, or subsurface discontinuities.

The eddy-current examination is sensitive to many factors that occur as a result of processing such as variations in conductivity, chemical composition, permeability, and geometry as well as other factors not related to the tubing. Thus, all received indications are not necessarily indicative of defective tubing. Basis of Application 6.

The practice or standard used and its applicable revision shall be identified in the contractual agreement between the using parties.

The applicable edition of Specification E shall be specified in the contractual agreement. Apparatus 7. Equipment may include a detector, phase discriminator, filter circuits, modulation circuits, magneticsaturation devices, recorders, and signaling devices as required for the particular application. Alternating current passes through the exciting coil which by reason of its proximity induces current in the tubular product. The sensor coil detects the resultant electromagnetic flux related to these currents.

The presence of discontinuities in the tubular product will affect the normal flow of currents and this change is detected by the sensor. The encircling coil technique is capable of examining the entire deg expanse of the tubular product.

Since the probe is generally small and does not encircle the article being examined, it examines only a limited area in the vicinity of the probe.

If it is desired to examine the entire volume of the tubular product, it is common practice to either rotate the tubular product or the probe.

In the case of welded tubular products frequently only the weld is examined by scanning along the weld zone. The depth of penetration of the interrogating magnetic fields into the tubular product may be smaller for this type of probe coil compared to the encircling coil.

NOTE 2Fill factor effect is an important consideration since coupling variations can affect the examination significantly. Probes generally consist of an exciting coil and sensing coil or Hall element mounted in a common holder.

A Hall element is a semiconductor that by reason of the Hall effect is capable of responding in a manner directly proportional to magnetic-flux density. However, when used with an exciting coil, it should be remembered that eddy-current flow is influenced by the excitation frequency.

NOTE 3Lift-off effect is an important consideration since coupling variations can affect the examination significantly. E 12 under conditions such as examining speed identical to those to be used in production examination of the tubular products.

It shall operate at a uniform speed with minimum vibration of coil, probe, or tube and maintain the article being examined in proper register or concentricity with the probe or examination coil. Where required, the mechanism shall be capable of uniformly rotating the tube or probe. If notches or holes are placed near only one of the ends, pass the tube through the system backwards and forwards.

It shall be of sufficient length to permit the required spacing of the artificial discontinuities at least 4 ft, and preferably longer. Artificial discontinuities made in the tube or pipe shall be centered as nearly as possible on one inside or outside diameter surface of the tube and shall preferably be of one of the following types: 7. Care should be taken during drilling to avoid distortion of the tube or pipe and hole.

Longitudinal or transverse notches or both may be used Note 4. Orientation, dimensions width, length, and depth , and configuration of the notches affect the response of the eddy-current system. Notch depth is usually specified as a percentage of nominal wall thickness of the tubular product being examined.

Notches may be placed on the outer, inner, or both surfaces of the reference calibration standard. Outer surface notches provide an indication of system response to discontinuities originating on the outer tube surface, whereas inner surface notches provide an indication of system response to discontinuities originating on the inner tube surface Note 5.

Procedure 9. The recommended maximum interval between re-standardization is four hours although more or less frequent re-standardization may be done by agreement between using parties, or whenever improper functioning of the equipment is suspected.

If improper functioning is found, re-standardize the apparatus and re-examine all tubes or pipes examined during the period since the last successful standardization. Set aside tubes or pipes with discontinuities indicated by the apparatus. It is recommended that tubes with discontinuity indications be re-examined in accordance with the purchase specification. The point in processing at which examination is made should be agreed upon by the supplier and the purchaser.

The tubes should be free of any substance that may interfere with the examination. NOTE 5The density of eddy currents decreases nearly exponentially with increasing distance from the surface nearest the coil, and the sensitivity to subsurface discontinuities decreases with the change in depth allowing the use of phase analysis techniques. The more commonly used operating frequencies are in the range, 1 kHz to kHz. The exact frequency used will depend on the application. ExampleIf thin-walled tubular products are to be examined or surface rather than subsurface discontinuities are to be detected, higher frequencies are used.

For heavy-walled tubes, subsurface discontinuities well below the surface require the use of a lower frequency. Choice of examination frequency will determine the size of discontinuity that can be detected. Adjustment and Standardization of Apparatus Sensitivity 8. Sensitivity varies significantly with distance from the examination coils.

For example, delta ferrite may be present in a welded product. Permeability may vary as a function of cold work. Some nickel alloys, such as Monel Alloy nickel-copper alloy , are magnetic in nature and others exhibit magnetism if there are slight residual stresses in the material. Do this 3 The weld area can usually be distinguished from the parent metal if the tubing has received little or no working after welding.

This occurs when the as-welded structure contains delta ferrite which is magnetic and can cause a high-background noise level or spurious indications, or both.

If drawn after welding, these effects may be reduced so that welded tubing cannot be distinguished from seamless tubing.

These effects do not necessarily preclude the eddy-current examination of as-welded tubing; however, the examination apparatus will probably require different adjustments for materials with as-welded and wrought structures. Thus, the minimum size discontinuity that can be detected may also be different. This bias field is generally applied by an encircling coil or yoke simultaneously with the field from the examination coil.

The apparatus is then adjusted to obtain an optimum signal-to-noise ratio. As a result, it may be desirable to prepare reference standards from each lot of material in order to take into account the effect of magnetic permeability. It may also be helpful to employ a magnetic-saturation device to minimize the effects of varying magnetic permeability.

Certain types of equipment can detect discontinuities at very slow speeds, while other types require a certain minimum speed. The examination speed may need to be linked to the speed at which the material is being processed at the point of examination. For this reason, sufficient work should be done to establish the sensitivity level and set-up required to detect natural discontinuities of consequence to the end use of the product.

Keywords Approved Aug. Also added a statement regarding differences in the depth of penetration of the magnetic field associated with probe type. ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility.

This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and if not revised, either reapproved or withdrawn.

Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards, at the address shown below.

Individual reprints single or multiple copies of this standard may be obtained by contacting ASTM at the above address or at phone , fax , or service astm.

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More E Changes in electromagnetic response caused by the presence of discontinuities are detected by the sensor, amplified and modified in order to actuate audio or visual indicating devices, or both, or a mechanical marker. Signals can be caused by outer surface, inner surface, or subsurface discontinuities. The eddy current examination is sensitive to many factors that occur as a result of processing such as variations in conductivity, chemical composition, permeability, and geometry as well as other factors not related to the tubing. Thus, all received indications are not necessarily indicative of defective tubing. Scope 1. Austenitic chromium-nickel stainless steels, which are generally considered to be nonmagnetic, are specifically covered as distinguished from the martensitic and ferritic straight chromium stainless steels which are magnetic.

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ASTM E426 - 16

Electromagnetic Eddy-Current Examination of Seamless and Welded Tubular Products, Titanium, Austenitic Stainless Steel and Similar Alloys1 This standard is issued under the fixed designation E; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the U. Department of Defense. Austenitic chromium-nickel stainless steels, which are generally considered to be nonmagnetic, are specifically covered as distinguished from the martensitic and ferritic straight chromium stainless steels which are magnetic.

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Changes in electromagnetic response caused by the presence of discontinuities are detected by the sensor, amplified and modified in order to actuate audio or visual indicating devices, or both, or a mechanical marker. Signals can be caused by outer surface, inner surface, or subsurface discontinuities. The eddy current examination is sensitive to many factors that occur as a result of processing such as variations in conductivity, chemical composition, permeability, and geometry as well as other factors not related to the tubing. Thus, all received indications are not necessarily indicative of defective tubing.

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