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IS 11732 (1995): Acceptance standards for dye penetrantinspection of steel castings [MTD 14: Foundry]

IS 11732: 1995

srrTa’ts W;r%

Indian Standard

ACCEPTANCESTANDARDSFORLIQUID PENETRANTINSPECTIONOFSTEELCASTING

( First Revision ) First Reprint APRIL 1997

ICS 17*140*80 : 19.100

0 BIS 1995

BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

December 1995 Price Group 3

Steel Castings Sectional Committee, MTD 17

FOREWORD

This Indian Standard ( First Revision ) was adopted by the Bureau of Indian Standards, after the draft finalized by the Steel Castings Sectional Committee had been approved by the Metallurgical Engineer- ing Division Council.

Liquid penetrant inspection is a physico-chemical non-destructive inspection procedure, designed to detect and expose surface discontinuities in engineering materials. The method can also reveal sub- surface d&continuities that have an opening to the surface to which the liquid penetrant has been applied. It has achieved recognition as a basic non-destructive test method owing to its advantages of rapidity, simplicity, coverage and economy with which it cm be used on a variely of materials and shapes with minimum capital investment. The objective is to detect cracks, porosity, laps, seams and other surface defects, rapidly and economically and with a high degree of reliability. The method is especially useful in case of steel castings made of non-magnetic material, to which the magnetic particle ins.pection method cannot be applied.

To aid the process of evaluation and determining the limits of acceptance of surface discontinuities detected by liquid penetrant inspection. it was considered necessary to evolve a specification for acceptance standards for liquid penetrant inspection.

The committee decided to revise this standard in view of the experience gained. Main modifications in this revision are as follows:

i) The title of the standard has been changed.

ii) ‘Standard Reference Pictures’ for liquid penetrant indications applicable for various levels of acceptance of quality have been modified.

iii) Details of procedure to follow for conducting the liquid penetrant test have been modified.

While preparing this standard, assistance has been derived from the following publications:

IS0 4987 : 1992 Steel castings - Penetrant inspection - International Standards Organization.

BS 4080 : Part 2 : 1989 Specification for seventy levels for discontinuities in steel castings. British Standards institution.

Indian Standard

ACCEPTANCE STANDARDS FOR LIQUID PENETRANT INSPECTION OF STEEL CASTING

/ First Revision )

IS 11732 .: l!F93

1 SCOPE

This standard determines the limits of acceptance of surface discontinuities detected by penetrant inspection for steel castings. The procedure to be adopted for this examination is as specified in IS 3658 : 1981. Liquid penetrant inspection is generally applicable to castings in finished or nearly finished state. However, it is applicable to in-process and maintenance inspection as well.

2 REFERENCES

The following Indian Standards are necessary adjuncts to this standard:

IS No. Title

3658 : 1981 Code of practice for liquid penet- rant t-law detection (jirst revision )

8780 : 1978 Code of practice for non-destruc- tive testing of steel castings

3 TERMINOLOGY

For the purpose of this standard, the definitions gtven in IS 3658 : 1981 shall apply.

4 SURFACE PREPARATION

4.1 The surface to be exammed shall be free from rust, dirt, welding spatter, lumps, grease, oil contamination, water, dust, etc. Any roughness which could mask, or interfere with the effectiveness of the examination shall be eliminated either by machining or grinding. If it is intended to also carry out magnetic particle inspection using a liquid ink, then the liquid penetrant inspection shall be carried out first.

4.2 The surface roughness for testing shall be as follows:

Acceptance Qua!ity Surface Roughness Level in t.bm ( micron )

(I) (2)

I 6.3 or less

12.5 or less

25 or less

4.3 The inspection shall be carried out before any surface treatment like scratching, hammer- ing, peening, etc. which may damage or dull the surface of metal and prevent penetration of the dye into .the surface discontinuities.

5 PRINCIPLE

5.1 Contrast Colour Liquid Penetrsnt with Nom- Fluorescent Developers

In this method, a coloured penetiant liquid, usually red, is applted to the surface to be inspected. Excess dye is removed by washing off the surface and the surface is then dried. Interpretation follows application of a develo- per, generally suspended in a volatile liquid.

NOTE - For certain applications, in order to minimix the risk of corrosion, the percentageof halogens and sulphur in the dye and developer material may be restricted by mutual agreement.

6 PROCEDURE

6.1 Cleaning .

Cleaning may be done using a wire brush or by grinding to remove dust, dirt, scales, etc. It is further essential to eliminate any trace of dust or grease .on the surface to be inspected by wiping with a lint-free cloth soaked tn one of the approved cleaning agents, such as trichloroethylene, acetone, alcohol, or isopropyl alcohol.

6.2 Drying

It is essential that the surface to be examined should be completely dry prior to the applica- tion of the dye penetrant and there should not remain either traces of water or the cleaning agent left in the defects.

6.3 Application of Dye

The dye may be applied either by immersion or paint brush or using a spray gun. The dwell time permissible for penetration is a critical factor. The minimum time to be allowed is 7 minutes but a longer period may be required for highly polished surfaces, very fine defects, or where temperatures are below 15°C and in such cases the time to be aliowed for penetra- tion shall be 10 to 20 minutes. The component

C

IS 11732 : 1995

temperatures outside the range of 10 to 50°C are not acceptable for such inspection unless mutually agreed to between the manu- facturer and the purchaser. The dye should not get dried up during the specified dwell time.

NOTE - Care should be taken to see that the test materials do not penetrate to inaccessible parts ( threaded holes, for example ) from which they cannot be clean-d after completion of the test.

6.4 Removal of Excess Dye

After the elapse of specified period of time for the penetration, excess dye must be removed from the surface in order to obtain an indica- ting contrast. Care must be taken for the dye lying in the defects not getting washed in the process. The excess is thus removed by using water or a suitable solvent which is at a temperature below 50°C and a pressure less than 3.5 kPa ( see 6.1 ). However, the surface should not be flushed with the cleaning medium The surface should be dried imme- diate!y and the developer applied.

6.5 Application of Developers

It should be applied .preferably by a spray gun having been mixed or shaken immediately prior to application in order to ensure a uniform suspension in the solution. Other techniques of application are permissible if, by their use, one can apply a light coating of uniform thickness without disturbing the dye lying in the defects. The application of a thick layer needs to be avoided in the process. The dwell time for the developer should be at least 1.5 times the dwell time specified for applied dye.

6.6 Examination

In view of the rapid diffusion of dye into the developer, it is preferable to examine the sur- face twice, once immediately after the applica- tion of the developer and a second time 11 to 15 minutes later. The indicated areas of defects are assessed at the abovesaad second stage and the overall time for the examination should not, in any case, be delayed beyond 30 minutes from the time of application of the developer.

7 INTERPRETATION OF RESULTS

7.1 Definitions

7.1.1 Indication

Any dye stain revealed by the application of the developer. 7.1.2 Positive Indications

Jndicutions that result from metal discontinui- ties. 7.1.3 Linear Indications

An indication with a major dimension three or more times its minor dimension (see Annex A ).

7.1.4 Non-Linear Indication

An indication with a major three times its ( see Annex A )

7.1.5 Aligned Indications

dimension less than minor dimension

Indications ( linear or non-linear ) at least three in number, that are in a line and separa- ted, one to the next, by a distance of less than 2 mm ( see Annex A ).

7.2 Evaluation of Indications

7.2.1 All indications in doubts must be treated as potential defects and re-examined to check the presence or the absence of a real defect. A prior re-dressing of the surface is envisaged.

7.2.2 Vague indications and areas of coloura- tion which could mask defects shall be trealed as unacceptable.

7.2.3 Indications having major dimension smaller than the limits given in Table I, under the column hceading ‘Major dimension of smallest indication considered’ for each severity level, shall not be taken into consideration and shall not be treated as significant.

7.2.4 All significant indications shall be evalua- ted as per the limits specified in Table 1.

7.2.5 It is to be considered that dye penetrant inspection like all methods of non-destructive inspection, forms a part of an overall assess- ment of quality of a casting and may not be treated as the sole criterion of acceptance.

8 ACCEPTANCE LIMITS

8.1 Castings are classified into five quality levels, 1, 2, 3, 4 and 5 as given in Table I according to the maximum permissible size and number of indications. Each inspected area shall be judged and classified into different levels by direct visual comparison with the acceptance standards detailed in Table 1 and shall be classified as levels I to 5, in descending order of quality ( see Fig. I to 5 ).

8.1.1 a) A frame measuring 105 mm x 148 mm shall .be moved over the area under inspection. The severi!y level shall abe determined by assessment of the discontinuity indications that appear at any one time within the frame.

8 When calculating the cumulative length of discontinuity indications, both aligned and non-aligned indica- tions shall be taken into account.

2

Table 1 Maximum Perrpissilale Extent of Indications

( CIauses 1.2.4, 8. I and 8.3 )

Nom-linear Indications T-------_A_----

Linear Inflicntiqs or Aljgqed up---_-------- *-----__---___~

Obscrr- ing.Indi- cations

Major Dimen-

sion of Smallest lndica-

tion Consi- dered (mm)

(3) (4) mm 1’5 2’0

XI 3’0 5’0

10’0

Number Maxi- Wall Thickness of Indi- mum cations Major

of Casting Less than 16 mm$

Dimen- p- .- -*- -_7 sions of Isola- Cumula-

Indivi- ted tive dual indica- indica- Indi- tion tion cationt

(5) (6) (7) (8) mm mm mm

8 3 2 4

Wall Thickness Wall Thickness of Casting from of Casting Over

16 to 50 mm: 50 rnrnt c--_*__-_Y - ._-_*__-_~ Isola- Cumula- Isola- Cumula-

ted tive ted tive indi- indi- ind i- indi-

cation cat ion cation cation

(9) (IO) (11) (12) mm mm mm mm

6’ 1; IS ::

* The criteria for severity levels 1 and 2 are extremely difficult to achieve except on precision castings and should be specified with caution.

t Schematic illustrations concerning non-linear indications for each of these severity levels are given jn Annex A for information, which is intended only as a guide.

$ For an area involving joining of more than one section thickness, as the thickness of the thinnest joining member.

the operative thickness shall be taken

c) The reference area for comparison 9 RECORD OF RESULTS may be chosen so as to make it reflect the lowest quality level attributable. If so specified at the time of enquiry and order,

the manufacturer shall furnish to the purchaser 8.2 The maximum permissible discontinuities the results relate to the quality level as indicated in the

of Liquid Penetrant Inspection carried out showing, for each casting or part

enquiry and order ( or drawing ). thereof, the following:

8.3 A set of reference pictures are given in Annex A to illustrate different quality levels. These reference pictures are for information only and the actual classification shall be in accordance with Table 1.

a)

b, c)

NOTE - Provided that the frame of 105 mm x d) 148 mm does not contain discontinuities which exceed the severity level specified in the order, there is no limit to the extent of discontinuities acceptable in the total area under inspection.

c)

3

the identity of the casting;

details of the technique used; the manufacturing stage at which the inspection was carried-out;

the identity and qualifications of the person carrying out the inspection; and

all discontinuities in excess of the speci- fied severity level.

-

IS 11732 : 1995

ANNEX A ( Clauses 7.1.3, 7.1.4, 7.1.5, 8.3 and Tublc 1 )

TYPICAL DISCONTINUITY DISTRIBUTION FIELDS FOR NON-LINEAR INDICATIONS

Table 1 should be consulted for exact details of allowable size and the number of indications.

Circular Linear Aligned

SR 1

.

l

6

. 0 l

.

I

l 0

4

8

l

.

l

SEVBRITY LEVEL SR 1 EIGHT NON-LINEAR INDICATIONS, 1.5 mm < D < 3 mm

4

-

IS 11732 : 1995

Q

m . .

0 0 . . . ’

$

. 0

. ,

0 .

0

l ’ . 0

SR 2

a . .

a

--- .m.-

SEVERITY LEVEL SR2 EIGHT NON-LINEAR INDICATIONS., D>2 mm

SR 3 0 v

e 0 e

SEVJZRITY LEVI~L SR3 TWELVE NON-LINEAR ~NDICATIOM, D > 3 mm

5

8 6

SWERITY LEVEL SR 4 TWENTY NON-LINEAR INDICATXOM, D> 5 mm

SR 5

. .

l

l

a

l @

l

Qnb

0

l

. . 9

l ulb

-- - _.-

SEVERITY LEVEL SR5 EIGHTY Two NON-LINEAR INDICATIONS, D > 10 mm 6

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Review of Indian Standards ,

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This Indian Standard has been developed from Dot: No. MTD 17 (3989).

Amend No.

Amendments Issued Since Publication

Date of Issue Text Affected

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