GB/T 42677-2023Non-destructive testing (NDT) methods of steel tubes - Liquid penetrant inspection of seamless and welded steel tubes for the detection of surface imperfections (English PDF)

Foreword

This document was issued on 6 August 2023 by the State Administration for Market Regulation; Standardization Administration of the PRC and takes effect on 1 March 2024.

It is a GB/T standard: recommended rather than compulsory, but it is the text a Chinese reviewer applies when assessing a submission.

1 Scope

GB/T 42677-2023 covers liquid penetrant inspection of seamless and welded steel tube for imperfections open to the surface, over all or part of that surface. The general requirements put the inspection at the end of the line: unless the product standard says otherwise, or supplier and purchaser agree otherwise, penetrant testing is done after rolling, heat treatment, cold working and the remaining production processes are finished — a step carried out afterwards can both create a defect and smear metal over one that is already there. The methods clause takes the sequence in order, penetrant applied to the surface, drawn into imperfections that are open to it, and the excess removed before the surface is examined, and the following clause deals with evaluating the indications that result. Acceptance is settled against a level: tube showing no indication above that level has passed, and tube showing indications above it falls under the rest of that clause. The test report, where required, goes to the purchaser carrying the number of this document among its contents. Penetrant testing works on material that cannot be magnetised, which is why it, rather than magnetic particle testing, is the surface method for stainless and other non-magnetic tube. It is used by tube mills, NDT service providers, fabricators, and purchasers writing an acceptance level into an order.

This document specifies the requirements for liquid penetrant inspection of seamless

and welded steel tubes for the detection of surface imperfections.

This document applies to the detection of imperfections on all or part of the surface of

steel tubes, and also applies to the detection of hollow profiles.

2 Normative references

The following referenced documents are indispensable for the application of this

document. For dated references, only the edition cited applies. For undated references,

the latest edition of the referenced document (including any amendments) applies.

ISO 3059 Non-destructive testing - Penetrant testing and magnetic particle testing -

Viewing conditions

ISO 3452-1 Non-destructive testing - Penetrant testing - Part 1: General principles

ISO 3452-2 Non-destructive testing - Penetrant testing - Part 2: Testing of penetrant

materials

ISO 9712 Non-destructive testing - Qualification and certification of personnel

NOTE: GB/T 9445-2015 Non-destructive testing - Qualification and certification of personnel

(ISO 9712:2012, IDT)

ISO 11484 Steel products - Employer’s qualification system for non-destructive

testing (NDT) personnel

3 Terms and definitions

For the purpose of this document, the terms and definitions defined in ISO 3452-1 and

ISO 11484 and the following apply.

3.1

tube

A long hollow product with open ends and a cross-section of any shape.

3.2

seamless tube

A hollow tube made by piercing a solid material, which is further hot or cold processed

into final dimensions.

3.3

welded tube

A hollow tube made from a strip by crimping and then welding, which may be further

hot and cold processed into final dimensions.

3.4

manufacturer

An organization that produces products in accordance with relevant standards and

declares that the delivered products comply with relevant standards.

3.5

agreement

The contract signed between the manufacturer and purchaser at the time of inquiry and

order.

4 General requirements

4.1 Unless otherwise specified in the product standard or agreed upon between both

supplier and purchaser, the liquid penetrant inspection shall be carried out after

completion of all the production processes of steel tubes (rolling, heat treating, cold and

hot processing, sizing, and straightening, etc.).

4.2 The surface of the steel tube to be inspected shall be clean enough and free of oil,

grease, sand, scale or any other foreign matter that may affect the accuracy of the

penetrant inspection results. The type of indications and the minimum imperfection

dimension that can be detected depend on the specific steel tube manufacturing process

and the surface finish.

4.3 The inspection shall be carried out by operators trained and qualified in accordance

with ISO 9712, ISO 11484 or equivalent standards and under the supervision of

competent personnel authorized by the manufacturer. In the case of third-party

inspection, this item shall be agreed upon between the supplier and purchaser.

The employer shall issue operating authorization certificates in accordance with

procedural documents. NDT operations shall be authorized by a level 3 NDT personnel

approved by the employer.

NOTE: The definitions of level 1, level 2, and level 3 can be found in the corresponding standards,

such as ISO 9712 and ISO 11484.

5 Inspection methods

5.1 General

5.1.1 A liquid penetrant is applied to the surface of the workpiece being inspected and

penetrates into the opening imperfections, and excess penetrant is removed; the surface

being inspected is dried and a developer is applied. The developer is used to adsorb the

penetrant penetrates into the imperfections and provide a high-contrast background for

indications. The indication of the penetrant can be a colored indication (visible under

white light) or a fluorescent indication (visible under ultraviolet light). For these two

penetrant inspection techniques, the following three penetrants can be used:

a) water washable type;

b) post-emulsifying type;

c) solvent removable type.

NOTE: The term “penetrant material” used in this document includes all penetrants, solvents,

cleaning agents, developers, etc. used in the inspection process.

5.1.2 For each steel tube to be inspected or each inspection position, it shall select one

of three types of penetrating materials for the inspection using colored penetrant

technique or fluorescent penetrant technique.

The general principles and verification methods for liquid penetrant inspection as

described in ISO 3059, ISO 3452-1, ISO 3452-2 shall be used.

5.2 Detection of imperfections and their classification

The liquid penetrant inspection is an effective means of detecting surface opening

imperfections (referred to as “surface imperfections” in this document). Typical surface

imperfections that can be detected by this method are cracks, seams, laps, cold shuts,

laminations, and porosity.

The liquid penetrant inspection cannot determine the nature, shape, and dimensions of

imperfections. The dimensions of the penetrant indication do not directly represent the

d) the penetrant should be applied by brushing or spraying. For local inspection of

steel tubes, dipping or flooding is not efficient, but can be used.

e) the penetration time shall not be less than the time recommended by the penetrant

system manufacturer, usually 3 min ~ 30 min.

f) when removing excess water washable penetrant or post-emulsifying penetrant, it

shall be flushed with water at a pressure of about 200 kPa (2 bar) under

appropriate black light conditions. The maximum pressure is 350 kPa (3.5 bar).

The temperature of the water used for flushing shall be lower than 40 degrees C. Use a

white wipes and clean, dry impurity-free material as much as possible to wipe

away excess solvent removable penetrant, until most traces of the penetrant are

removed. Use a clean, lint-free material slightly moistened with detergent to

gently wipe the surface, until all traces of excess penetrant are removed from the

surface of the workpiece being inspected. It is prohibited to rinse the surface with

solvent after using the penetrant and before developing.

g) dry the washed surface, use a clean and dry white stain-free material to assist in

wiping, or dry the surface with hot air at a pressure lower than 200 kPa (2 bar)

and a temperature lower than 70 °C. Drying is usually by natural evaporation after

solvent removal, so no other drying techniques are required. The temperature of

the steel tube shall not exceed 50 °C, unless otherwise agreed upon between the

purchaser and manufacturer.

h) the wet developer shall be applied by spraying, to ensure that the area being

inspected is completely covered with a thin and uniform developer film; the dry-

powder developer shall be applied either by immersing the part being inspected

into a powder spray cabinet with dry-powder developer, or by spraying dry-

powder developer through a powder bulb or a powder spray gun (conventional or

electrostatic), to ensure that the powder is evenly sprayed on the surface of the

test piece being inspected.

i) the development time is calculated from the time after the wet developer is dry or

the dry developer is applied. Under normal circumstances, the development time

is equal to the penetration time, usually 5 min ~ 30 min. If the indication size does

not change, the development time is allowed to exceed 30 min.

j) the inspection of the areas being inspected is carried out after 5.3 i), and it shall be

ensured that there is enough penetrant in the imperfection to be adsorbed to the

surface of the workpiece by the developer. If agreed upon between the two parties,

a contrast agent can be applied during observation. During fluorescent penetrant

inspection, the inspection shall be carried out in a dark area where the visible

illumination does not exceed 20 lx, and UV-A ultraviolet radiation is used to make

the ultraviolet illumination of the area being inspected on the surface of the

workpiece to be not less than 10 W/m2. During colored penetrant inspection, the

the distance between adjacent indications is less than the length of the larger of

the two indications, the two adjacent indications are regarded as one indication,

and the indication length shall be the sum of the length of each indication and the

length of the spacing.