Section 15 — Inspection

Eddy Current Examination

IPE Engineering Practice IPE-EP-15-2-2

Document number: IPE-EP-15-2-2 · Section: 15 — Inspection

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SCOPE

This practice covers the minimum requirements to perform all methods of eddy current tube testing, magnetic flux leakage, and IRIS tube testing by contractors working on equipment belonging to Inflection Point Engineering, LLC. These methods are used for volumetric examination of installed heat exchanger and airfin tubes for detection of I.D. and O.D. discontinuities.

(*) Inspection contractors selected to bid on Inflection Point Engineering, LLC work shall submit their procedures for review and approval by the responsible Inflection Point Engineering, LLC Inspection Authority during the bidding process.

Inspection contractors who have had their procedures approved may perform inspections in accordance with the approved procedures.

Any deviation to this practice shall be approved by the procedure described in EP 1–1–3.

An asterisk (*) indicates that a decision by the Owner’s Level III or Inspection Authority is required or that additional information may be included by the purchaser.

REFERENCES

The latest edition of the following standards and publications are referred to herein.

STANDARDS AND PUBLICATIONS

DEFINITIONS

• Acceptance Standard - In tubing inspection, a tube used to establish the acceptance level with artificial discontinuities as specified by the contractor’s written procedures
• Eddy Current - An electrical current caused to flow in a conductor by the time or space variation, or both, of an applied magnetic field.
• Eddy Current Testing - A nondestructive testing method in which eddy current flow is induced in the test object. Changes in the flow caused by variations in the specimen are reflected into a nearby coil, coils, or Hall effect device for subsequent analysis by suitable instrumentation and techniques.

• Electromagnetic Testing - A nondestructive test method for materials, including magnetic materials, that uses electromagnetic energy having frequencies less than those of visible light to yield information regarding the quality of testing material.
• Ferromagnetic Material - A material that, in general, exhibits the phenomena of magnetic hysteresis and saturation, and whose permeability is dependent on the magnetizing force.
• Fill Factor - For internal probe electromagnetic testing, the ratio of the effective cross-sectional area of the primary internal probe to the cross-sectional area of the tube inside diameter.
• IRIS - Internal rotary inspection scan, is a total immersion ultrasonic technique which details the through wall thickness of tubing.
• Magnetic Flux Leakage - The excursion of magnetic lines of force from the surface of a test specimen.
• Magnetic Saturation - That degree of magnetization where a further increase in magnetizing force produces no significant increase in magnetic flux density (permeability) in a specimen.
• Non-ferromagnetic Material - A material that is not magnetizable and hence, essentially not affected by magnetic fields.
• Owner - Inflection Point Engineering, LLC.
• Purchaser - The party placing a direct purchase order. The purchaser is the Owner’s designated representative.
• Reference Standard - A reference used as a basis for comparison or calibration. In tubing inspection, a tube with artificial discontinuities used for establishing the test sensitivity setting and for periodically checking and adjusting sensitivity setting as required.
• Plant Inspection Authority - That person or body appointed by Management to be responsible for examination and certification of equipment utilized within the plant. Management may appoint more than one Inspection Authority in order to cover specialized equipment such as rotating, instrumentation and electrical equipment.
• Rejection Level - The value established for a test signal above or below which test specimens are rejectable, or otherwise distinguished from the remaining specimens.
• Remote Field Eddy Current - An electromagnetic technique used to identify corrosion in ferromagnetic tubes.

DESCRIPTION OF TEST METHODS

• Eddy current testing is an electromagnetic technique used to examine nonferrous materials, single frequency or multiple frequency techniques using, bobbin type, absolute or differential coils, or combinations of coils are used for volumetric examination of tubing for I.D. and O.D. discontinuities. A localized alternating-current loop (eddy) is induced in the tube. Inductive reactance of the probe to the magnetic field of induced current indicates subsurface flaws. Induced currents in the range of 200-Hz to 2-Mhz are used. The technique is accurate for detection of general thinning >10% of wall thickness, uneven wall thinning >20% of wall thickness, and pitting >0.05 inch dia, at fairly rapid test speeds.
• Remote field eddy current testing is an electromagnetic technique used to examine ferromagnetic tubing. Unlike eddy current, RFT operates at lower frequencies, in the 50 to 500 Hz range for carbon steel. An RFT probe, bobbin type, has an exciter coil and two or more detector coils. An AC magnetic field is generated by the exciter coil and travels out through the tube wall and along the tube, and passes back through the tube wall at a distance of about three tube diameters. The tube wall thickness is directly related to the travel time, or the phase of the AC magnetic field. The technique is accurate for detecting wall thinning >10% of wall thickness at fairly rapid test speeds.
• Magnetic Flux Leakage testing is an electromagnetic technique used to examine ferromagnetic tubing. A magnetic field is imposed on the tube. The field permeates and magnetizes the tube wall and a detector coil detects changes in the field that are characteristic of surface and subsurface flaws. This technique can be used for rapid scanning of tubes. The technique is accurate for detecting general thinning >30% of wall thickness, uneven wall thinning >40% of wall thickness, and pitting >0.05 inch dia.
• IRIS is an immersion ultrasonic technique that uses a high speed rotating transducer to examine the complete circumference of both ferrous and non-ferrous tubing. The technique is very accurate for measuring tube wall thickness and locating pitting to about 0.05 inch dia. and

0.02 inch deep. This technique is typically very slow and requires very clean tube I.D.’s.

RESPONSIBILITIES

• The Chief Inspector, Inspection Authority, or the responsible plant inspector shall review the procedures and qualifications of contractor test operators before the testing of exchanger or other tubes begins.
• The Chief Inspector, Inspection Authority, or the responsible plant inspector shall review and approve the contractors test procedures before the contractor arrives on-site.
• The responsible plant inspector shall furnish the contractor all information in 8.1 before the start of the job.
• The lead contractor inspector or technician shall be responsible for assuring that he and all contractor personnel follow all Inflection Point Engineering, LLC safety practices applicable for the work being conducted.
• The lead contract inspector or technician shall be responsible for reporting the results of all testing conducted to the responsible plant inspector.

• Personnel performing examinations are responsible for complying with all requirements of this practice and the contractors written procedure.
• The contractors Level III is responsible for assuring that all personnel performing examinations for Inflection Point Engineering, LLC facilities are trained, qualified and certified in accordance with 6.0. The Level III shall also be responsible for assuring that examinations are conducted in accordance with the contractors approved written procedures.

CERTIFICATION OF PERSONNEL

• Personnel performing eddy current and IRIS testing in IPE Facilities shall be certified in accordance with ASNT-SNT-TC-1A and their employer’s written practice.
• Only personnel certified Level II or Level III shall evaluate test results.
• Level II or Level III personnel shall perform the operational portion of the examination.
• Level I personnel shall only be allowed to assist with the operational portion of the examination under the direct supervision of Level II or Level III personnel.

SAFETY

• Contractor employees working at IPE facilities shall complete all safety training required by that site before examinations can begin.
• Contractor employees working at IPE facilities shall perform all work in accordance with the contractor’s written practices, and ’s Safe Practice Procedures.
• All equipment used by contractor personnel shall be used within the safe operating limits described by the manufacturer of the equipment.
• All electric powered equipment used by contractor personnel shall be protected by explosion proof connectors, and ground fault circuit breakers as required by Inflection Point Engineering, LLC or contractor procedures.
• All site permits shall be obtained by the contractor prior to entry into the unit or area where the equipment to be examined is located.

PREPARATIONS BEFORE INSPECTION

• (*) The following information concerning the equipment to be inspected shall be furnished to the contractor before the job starts:
• Complete tube description including size and metallurgy.
• Historical information including previously known corrosion conditions.
• Sketch or drawing of the tube bundle including tubesheet face.
• Inspection plan including the number of tubes to be inspected and the pattern for their inspection, if any.
• Access to the tubes to be inspected shall be provided by Inflection Point Engineering, LLC or their maintenance contractors.
• Scaffolds shall be provided by Inflection Point Engineering, LLC or their maintenance contractors when needed.

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Electrical connections, air, and water shall be provided at the work site by Inflection Point Engineering, LLC or their maintenance contractors as needed.

The inside diameters of tubes shall be cleaned before testing as needed to assure reliable test results. Cleaning shall be done by Inflection Point Engineering, LLC or their maintenance contractors.

Tubes shall typically be cleaned by high pressure water washing, but in some cases mechanical cleaning may be needed to prepare the tube ID’s for examination.

(*) Personnel conducting tube examinations shall report any problems encountered with dirty tubes to the responsible Inflection Point Engineering, LLC Inspector. The inspector shall decide if additional cleaning is required.

EXAMINATION REQUIREMENTS & CALIBRATION OF TEST EQUIPMENT

All examinations shall be performed in accordance with a written procedure that contains sufficient detail to insure equipment is operated in accordance with the instrument manufacturer’s operating instructions.

The contractor shall be equipped with appropriate calibration standards for the tube size and metallurgy to be examined.

The calibration tube shall contain artificial or natural discontinuities that adequately simulate the discontinuities expected during the examination. Artificial discontinuities may be in the form of flat bottom holes, grooves, wall reductions, or other suitable simulations. Each standard shall be properly identified.

A copy of the strip chart or computer print out of the calibration conducted immediately prior to the examination, and for each calibration check conducted during the examination procedure, shall be included with test documentation. Calibration confirmation shall be performed every 4 hours, when equipment has been idle for more than one hour, after a power loss, if any of the test system equipment is changed, or if calibration is in doubt. If at any check the equipment is found to be out of calibration, the system shall be recalibrated, and the tubes examined since the last calibration shall be reexamined in reverse order until it is determined that the examinations are valid. If needed all tubes since the last calibration shall be reexamined.

After completion of the examination a calibration check shall be conducted. The strip chart or computer print out of this calibration check shall also be included with the test documentation.

Calibrations shall be performed by pulling probes through the tube standards at the speed to be used during the inspection.

Each defect indicated on the strip chart or computer print out of the calibration shall be marked by hand on the chart or print out indicating what the defect is.

Test standards shall be manufactured in accordance with the contractors written procedures, and ASME Sec V, Article 8, Appendix I.

Equipment and materials used to conduct tube examinations for Inflection Point Engineering, LLC facilities shall have adequate ranges and accuracy and shall be calibrated or certified as required by the contractors written procedures and applicable codes.

EXAMINATION

• (*) Unless agreed otherwise, by the responsible plant inspector, the contractor shall provide automated probe pulling devices to assure a consistent speed of examination.
• All examinations shall be recorded on a multi-channel strip chart recorder, magnetic tape, optical disc, or on a computer print out.
• Suitable charts or print outs of all examinations shall be included with the test documentation.
• (*) If agreed to by the responsible plant inspector, the results of testing may be summarized in a report format suitable for Inflection Point Engineering, LLC.
• All examination parameters shall be reproducible.
• A technique sheet or examination procedure report shall be completed by the contractor for each examination conducted. This document shall be included in the examination report, and shall include all information needed to reproduce the examination with comparable results.
• The technique sheet or examination procedure shall be signed and dated by the Lead Technician.
• Only equipment included in the contractor’s approved written procedures shall be used to conduct tube examinations for Inflection Point Engineering, LLC.
• All examinations shall be conducted in accordance with contractor procedures that have been reviewed and approved by the Inflection Point Engineering, LLC Chief Inspector, Inspection Authority, or the responsible plant inspector.
• (*) Unless agreed to prior to testing, the entire length of all tubes shall be examined. Any areas of tubes that cannot be examined shall be noted on the test reports. The reason or reasons for not examining areas of tubes shall be documented. In most cases, U-bends will not be examined through the bend unless special arrangements are made.
• Location indications, such as tube baffles, shall be marked on strip charts and computer print outs for reference.
• For reference, a tubesheet map shall be made up showing the location of each tube examined. The tubesheet map shall be referenced for positive location of the tubes.

EVALUATION OF INDICATIONS

• A preliminary evaluation shall be conducted for all tubes examined in the field. This evaluation shall be conducted to locate any anomalies from a normal pattern on the eddy current instrument, the strip chart, or the computer print out.
• The normal pattern shall be determined by familiarization with the characteristic signals generated from the tube supports, baffles, tube sheet, U-bends or other internal structures within the component being examined.
• (*) Unless otherwise agreed to prior to testing, all indications equal to or greater than 20 percent of wall degradation shall be reported.

• (*) Unless otherwise agreed to prior to the examination, the examination as a minimum shall include all tubes around the outer circumference of each tube bundle examined, and every fifth tube in each tube row.
• (*) The rejection criteria for indications shall be furnished by Inflection Point Engineering, LLC prior to each examination.
• If during the examination a rejectable indication is noted, the tubes surrounding the rejectable tube shall be examined until no further rejectable indications are noted.

REPORTING OF INSPECTION RESULTS

• Prior to leaving the job site or when requested, the contractor shall furnish the responsible plant

inspector a preliminary examination report with a summary of all tubes examined.

• The contractor shall furnish Inflection Point Engineering, LLC with a complete final examination report within 30 days after the examination is completed.
• The final examination report shall contain a summary of all tubes examined and all the documentation required in other sections of this practice. The minimum required information shall include:
• Customer information, plant, location, etc.
• Exchanger ID & Asset Number
• Process Name
• Exchanger information, tube material, size.
• Calibration tube material, size, discontinuities.
• Test equipment model, manufacturer, S/N, and calibration date.
• Probe driver information, manual, probe gun, etc.
• Interpretation method and associated description.
• Probe(s) type, manufacturer and serial nos.
• Frequency(s), mode, filters
• Data recording equipment information.
• Date(s) of the examinations.
• Test personnel name(s) and certification information.
• Calibration strip chart or computer print out.
• Test results

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