GB/T 34370.9-2020 PDF English
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Nondestructive testing of amusement equipments -- Part 9: Magnetic flux leakage testing
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GB/T 34370.9-2020: PDF in English (GBT 34370.9-2020) GB/T 34370.9-2020
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 97.200.40
Y 57
Nondestructive Testing of Amusement Equipment – Part 9:
Magnetic Flux Leakage Testing
ISSUED ON: NOVEMBER 19, 2020
IMPLEMENTED ON: JUNE 1, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative References ... 4
3 Terms and Definitions ... 4
4 Method Summary ... 5
5 Safety Requirements ... 6
6 Personnel Requirements ... 7
7 Testing Equipment and Instruments ... 7
8 Testing Process Procedures ... 8
9 External Magnetic Flux Leakage Testing of in-Use Pipes and Plates ... 10
10 Magnetic Leakage Detection of in-Use Wire Ropes and Cables ... 14
11 Inspection Records and Reports ... 17
Appendix A (Informative) Preparation Requirements for Typical Component and Test
Piece ... 19
Nondestructive Testing of Amusement Equipment – Part 9:
Magnetic Flux Leakage Testing
1 Scope
This Part of GB/T 34370 specifies the method of magnetic flux leakage testing and result
evaluation for amusement equipment.
This part is applicable to the magnetic flux leakage testing of ferromagnetic material
components such as steel pipes with an outer diameter of no less than 38mm and a wall
thickness of no more than 20mm, steel plates with a thickness of no more than 20mm, and steel
wire ropes and cables with a diameter of no less than 6mm for amusement equipment.
2 Normative References
The following documents are essential to the application of this Document. For the dated
documents, only the versions with the dates indicated are applicable to this Document; for the
undated documents, only the latest version (including all the amendments) is applicable to this
Document.
GB/T 20306 Amusement devices terminology
GB/T 20737 Non-destructive testing - General terms and definitions
GB/T 34357 Non-destructive testing – Terminology - Terms used in magnetic flux leakage
testing
GB/T 34370.1 Nondestructive testing of amusement equipment - Part 1: General
requirement
GB/T 34370.5 Nondestructive testing of amusement equipment - Part 5: Ultrasonic testing
GB/T 34370.6 Nondestructive testing of amusement equipment - Part 6: Radiographic
testing
3 Terms and Definitions
For the purposes of this Document, the terms and definitions given in GB/T 20306, GB/T 20737,
GB/T 34357 and GB/T 34370.1 and the following apply.
Figure 2 – Schematic Diagram of Typical Magnetic Flux Leakage Signal
4.2 Application of magnetic flux leakage testing method
4.2.1 Testing time:
a) Testing during the manufacturing process;
b) In-service testing.
4.2.2 Main uses:
a) Testing and evaluation of cracks, mechanical damage, and non-magnetic inclusions
generated during the manufacturing process of materials or components;
b) Testing and evaluation of metal losses such as cracking, corrosion, and mechanical
damage generated during the service of equipment or components.
4.3 Related influencing factors
The related influencing factors of magnetic flux leakage testing method are:
a) Scanning speed and direction;
b) Lift-off value;
c) Geometric shape and electromagnetic characteristics of the component under test;
d) Sensitivity of the testing instrument.
5 Safety Requirements
This Clause does not list all safety requirements for testing. Users of this Part shall establish
safety guidelines before testing.
Safety requirements during the testing process include at least:
a) Testing personnel shall comply with the on-site safety requirements of the equipment
under test; and wear protective work clothes and relevant protective equipment according
to the requirements of the testing site;
b) Attention shall be paid to avoid various safety hazards, such as bumps, electric shocks,
falls, squeezes, shears, entanglements, slips, drowning, scalds, etc.;
c) When operating at high altitudes, factors such as the fall of personnel and testing
equipment shall be considered; and necessary protective measures shall be taken;
d) During transportation, storage and handling of magnetization units, strong magnetism
shall be avoided to affect personal safety, equipment, instruments and the environment;
e) During testing, attention shall be paid to personal injuries and equipment damage caused
by magnetic field attraction and the influence of other auxiliary electronic equipment.
6 Personnel Requirements
Personnel engaged in magnetic flux leakage testing of amusement equipment shall comply with
the relevant provisions of GB/T 34370.1.
7 Testing Equipment and Instruments
7.1 Magnetic flux leakage testing system
7.1.1 The magnetic flux leakage testing system shall at least include a power supply, a
magnetization unit, a magnetic field sensor, a signal acquisition unit, a signal display (or alarm)
unit, a signal storage unit, etc., and a demagnetization unit and a position recording unit shall
be provided, if necessary.
7.1.2 The magnetic flux leakage testing system shall have the function of analyzing and
displaying the position and dimension or size of the found defects.
7.2 Test pieces
7.2.1 Calibration test pieces
7.2.1.1 The calibration test pieces are mainly used for functional testing of each independent
channel of the magnetic flux leakage testing instrument, adjusting the testing sensitivity,
adjusting the testing parameters and ensuring the accuracy of the testing results.
7.2.1.2 The calibration test pieces shall be made of materials with the same or similar
ferromagnetic properties as the object under test.
7.2.2 Comparison test pieces
7.2.2.1 The comparison test pieces are mainly used for the signal equivalent or quantitative
evaluation of defects in actual testing and for determining the acceptance level.
7.2.2.2 The comparison test pieces shall have the same or similar specifications, designations,
heat treatment status, surface status and electromagnetic properties as the object under test.
7.2.3 Manufacturing requirements
7.2.3.1 The surface of the test piece shall not be stained with foreign matter and shall not have
p) Post-testing operation requirements;
q) Evaluation and handling of test results;
r) Testing records, reports and data archiving;
s) Preparation (level), review (level) and approval person;
t) Date of formulation.
8.2 Testing work instructions or process cards
For the magnetic flux leakage testing of each type of structure, the magnetic flux leakage testing
work instructions or process cards shall be formulated according to the actual situation,
GB/T34370.1, this Part and the general testing process regulations.
The content of the testing process card shall at least include:
a) Work instructions or process card number;
b) Testing execution standards;
c) Information on the equipment and components under test: name, model, number, material,
specification, size, heat treatment status, welding type, etc.;
d) Testing equipment: name, specification, model, number, etc.;
e) Sensor model, excitation method;
f) Testing timing;
g) Testing area and surface requirements;
h) Schematic diagram of the testing position;
i) Testing environment requirements;
j) Scanning direction, scanning speed and scanning coverage area;
k) Lift-off;
l) Materials of comparison test pieces and calibration test pieces;
m) Requirements of marking and raw data recording for testing;
n) Post-testing operation requirements;
o) Evaluation and handling of testing results;
p) Records of the testing process;
q) Signatures and dates of the compilation (level) and review (level) personnel.
9 External Magnetic Flux Leakage Testing of in-Use Pipes
and Plates
9.1 Testing objects
The testing objects are steel pipes with an outer diameter of no less than 38mm and a wall
thickness of no more than 20mm and steel plate components with a thickness of no more than
20mm. For larger components that can be tested for magnetic flux leakage from the inside, refer
to this Clause.
9.2 Testing system
9.2.1 Testing equipment
The testing equipment generally consists of a power supply, a magnetization unit, a probe, a
scanning unit, a signal processing unit and a recording unit, etc. In addition to meeting the
requirements of 7.1, it shall also meet the requirements of 9.2.2 ~ 9.2.9.
9.2.2 Magnetization unit and probe
Select appropriate magnetization units and probes according to the curvature of different
components under test.
9.2.3 Channels
The instrument and probe shall have enough channels; and the probe shall provide the coverage
of each testing channel.
9.2.4 Scanning unit
The scanning unit shall match the curvature of the component under test; and can be scanned
manually or electrically, with a maximum scanning speed of no less than 0.3m/s.
9.2.5 Sensitivity
For wall thickness less than or equal to 8mm, when the coating thickness is less than 6mm,
artificial defects 20% of the surface thickness of the object under test can be detected; when the
wall thickness is greater than 8mm or the coating thickness is greater than 6mm, the testing
sensitivity shall be determined by negotiation between the user and the testing unit.
9.2.6 Signal display
a) Equipment manufacturing documents: product certificate, quality certification documents,
completion drawings, etc.;
b) Equipment operation record data: start-up and shutdown conditions, operating parameters,
working medium, load changes, and abnormal conditions during operation, etc.;
c) Testing data: previous testing reports;
d) Other data: repair and modification documents, etc.
9.4.2 On-site survey
Investigate the equipment and components under test on site to find out and try to eliminate
factors that may affect the test results. At the same time, locate and mark the components under
test.
9.4.3 Preparation of testing process card
For each testing equipment or each component under test, a magnetic flux leakage testing
process card shall be prepared according to the used instruments and the actual situation on site,
in accordance with GB/T 34370.1, this Part and the general testing process regulations.
9.4.4 Determination of testing conditions
The surface of the component under test shall be free of obstacles and foreign objects that may
affect the testing. If there are grease, dirt, burrs and oxide scale that may affect the testing, they
shall be removed to ensure the normal testing.
9.4.5 Determination of scanning method
The magnetization direction and scanning method shall be determined according to the purpose
of magnetic flux leakage testing and the shape and size of the component under test.
9.4.6 Instrument debugging
Before the testing, the instrument shall be checked and debugged for system functionality.
9.4.7 System calibration
9.4.7.1 The probe, magnetization unit and system host shall be calibrated before each testing to
ensure the accuracy of the test results. Each calibration shall be recorded. System calibration
includes position calibration and sensitivity calibration.
9.4.7.2 The sensitivity of the magnetic flux leakage testing equipment shall be checked using a
comparison test piece in the following situations:
a) Before and after each testing;
b) When the testing equipment is suspected to be operating abnormally;
c) During continuous testing, check once every 8 h;
d) When there is a dispute between the parties to the contract or it is deemed necessary.
9.4.8 Testing
9.4.8.1 If the purpose of the test is to find volume defects, a single-direction scanning method
can be used. If the purpose of the test is to find cracks, an orthogonal scanning method shall be
used.
9.4.8.2 The scanning can be performed in manual or automatic mode, and the scanning speed
shall be kept as uniform as possible.
9.4.8.3 During the scanning test, the effective overlapping between adjacent scanning bands
shall be ensured (generally no less than 10%, which can be adjusted appropriately according to
the on-site conditions) to avoid missed testing.
9.5 Evaluation and processing of test results
9.5.1 Evaluation of test data
9.5.1.1 During the testing, the equivalent depth of the defect that needs to be alarmed shall be
determined according to the user's requirements. When a defect signal exceeding this depth is
detected, the instrument shall alarm.
9.5.1.2 For the positions where the alarm occurs, re-scan and verify in the direction of 90°
perpendicular to the original scanning direction or in multiple directions to confirm whether it
is a real defect.
9.5.1.3 If it is determined to be a real defect, the testing personnel shall mark the defect location
found on the component and the drawing respectively, that is, the position of the unacceptable
signal.
9.5.2 Processing of unacceptable signals
9.5.2.1 First, the visual inspection and hammer tapping methods are used to distinguish whether
the unacceptable signal is a defect on the outer surface or the inner surface.
9.5.2.2 For defects on the outer surface, the depth of the defect can be directly measured by a
depth gauge.
9.5.2.3 For defects on inner surface, ultrasonic or radiographic detection methods shall be used
to measure the depth of the defects more accurately. The ultrasonic detection method shall be
implemented in accordance with GB/T 34370.5, and the radiographic detection method shall
be implemented in accordance with GB/T 34370.6.
The system function of the equipment shall be verified using a calibration test piece before and
after the implementation of the testing. After the system encounters a fault or is repaired, a
system function check is required.
10.2.8 Maintenance of testing equipment
Before the testing is implemented, the testing equipment shall be maintained and functionally
checked to ensure that the instrument functions normally. When testing on site, if the test results
of the equipment are in doubt, the equipment shall be functionally checked and adjusted; and
the results of each maintenance check shall be recorded.
10.3 Accessories
10.3.1 Calibration test piece
The preparation of the calibration test piece refers to A.5.
10.3.2 Comparison test piece
10.3.2.1 The comparison test pieces are used to evaluate the equivalent of the defects under test.
10.3.2.2 Materials with the same geometric dimensions and similar electromagnetic properties
as the object under test shall be selected; and comparison test pieces shall be made according
to the test requirements of the object under test.
10.3.2.3 The preparation of comparison test pieces refers to A.6.
10.4 Testing procedure
10.4.1 Document review
The document review shall include the following:
a) Equipment manufacturing documents: product certificate, quality certification documents;
b) Equipment operation record: start-up and shutdown conditions, operating parameters,
load changes, and abnormal conditions during operation;
c) Inspection documents: previous inspection reports;
d) Other documents: repair and modification documents, etc.
10.4.2 On-site investigation
Conduct an on-site investigation around the component under test to identify and try to
eliminate factors that may affect the test results, such as vibration and surrounding
ferromagnetic objects. At the same time, locate and mark the components under test.
10.4.3 Determination of testing conditions
The surface of the component under test shall be free of obstacles that affect the testing and
foreign matters that interfere with the testing. If there are burrs and oxide scales that affect the
testing, they shall be removed to ensure that the test is carried out normally.
10.4.4 Determination of scanning method
Determine the magnetization direction, scanning method and scanning speed according to the
purpose of magnetic flux leakage testing and the size and installation method of the component
under test.
10.4.5 Instrument debugging
Before the testing, the instrument shall be checked and debugged for system functionality.
10.4.6 System calibration
10.4.6.1 The probe, magnetization unit and system host shall be calibrated before each testing
to ensure the accuracy of the test results. Each calibration shall be recorded. System calibration
includes position calibration and sensitivity calibration.
10.4.6.2 The sensitivity of the magnetic flux leakage testing equipment shall be checked using
a comparison test piece in the following situations:
a) Before and after each testing;
b) When the testing equipment is suspected to be operating abnormally;
c) During continuous testing, check once every 8 h;
d) When the parties to the contract have a dispute or deem it necessary.
10.4.7 Testing
10.4.7.1 To ensure the repeatability of the test results, at least 2 repeated operations shall be
performed.
10.4.7.2 The scanning can be performed in manual or automatic mode, and the scanning speed
shall be kept as uniform as possible.
10.4.7.3 When the entire working length of the component needs to be scanned multiple times,
the direction of the magnetizer pole should be adjusted to be consistent with the component
each time; and the effective overlapping between adjacent scanning sections shall be ensured
during the scanning test (generally no less than 1m, which can be adjusted appropriately
according to the on-site conditions) to avoid missed testing. When testing the same component,
it should use one instrument to complete the test according to the same standard.
position is about 0.5m apart; and there are 1, 2, and 3 broken wires in 3 places, and the distance
from the end of the rope/cable is no less than 400mm. The broken wire requires a wire diameter
of ≥1.5mm and a break gap of ≥2mm.
A.5.2 Calibration test piece for the metal cross-sectional area loss of rope/cable
The steel pipe used for the calibration test piece for metal cross-sectional area loss of rope/cable
shall be selected according to the upper and lower limits of the outer diameter of the rope/cable
that the tester can test. The metal cross-sectional area of the steel pipe is the same as the metal
cross-sectional area of the rope/cable with the same diameter. It is made by one of the following
methods.
Method-I: The length of the test piece is no less than 2.5m, and the curvature is no more than
15mm/m. The artificial defect is a longitudinal groove; the length of the groove is no less than
300mm, the interval is no less than 300mm, the distance from the end of the pipe is no less than
400mm, the width and depth are determined according to the percentage of cross-sectional area
reduction, and the metal cross-sectional area is required to change by 1%, 2%, 3%, and 4% in
4 places.
Method-II: The length of the test piece is no less than 1m, and the curvature is no more than
15mm/m. Insert multiple steel wires of equal diameter into the steel pipe to increase the total
area of the metal cross-sectional area. The cross-sectional area of the steel wire is 1% or less of
the cross-sectional area of the steel pipe; and the cross-sectional area deviation of multiple steel
wires is less than 1%. During the testing, put the steel pipe into the magnetic flux leakage testing
sensor; and place the sensor in the middle of the steel pipe; and then insert the steel wires one
by one to increase the total area of the metal cross-sectional area by 4%.
A.6 Comparison test piece of rope/cable
A.6.1 Broken wire comparison test piece of rope/cable
The wire rope used for the broken wire comparison test piece of rope/cable shall match the wire
rope under test.
The length of the test piece shall be no less than 2.5m, and the curvature shall be no greater
than 15mm/m. The broken wires are made on the rope/cable by manual sawing. The broken
wire positions are about 0.5m apart; and there are 1, 2, and 3 broken wires in 3 places; and the
distance from the end of the rope/cable is no less than 400mm. The broken wire requires a wire
diameter of ≥1.5mm and a break gap of ≥2mm.
A.6.2 Comparison test piece for metal cross-sectional area loss of rope/cable
The steel pipe used for the comparison test piece for metal cross-sectional area loss of
rope/cable shall have the same outer diameter and metal cross-sectional area as the steel wire
rope under. It is made by one of the following methods.
...... Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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