wings corporation doc. no. : wd14-001e japan …wingshome.co.jp/introduction/section6_e.pdfcause-...

The copyright is in Takashi Yagisawa

Translation Start Date: August 8th, 2018

http://wingshome.co.jp/introduction_e.html

WINGS CORPORATION

Japan

Doc. No. : WD14-001E

Sheet 90 of 110

Rev. No. : E0

Title: Introduction of the inspection and testing for the

industrial valves

6. VISUAL INSPECTION

This inspection is conducted by visual inspection etc. of the appearance etc. of the target item.

In this chapter, we will mainly explain the cast material, forged material, welded part, processed surface and

painted ground treatment surface.

Note:

For ASME SECTION V, ARTICLE 9, VISUAL EXAMINATION, please refer to it as follows.

· The visual acuity of the inspector: The following English words created by Time New Roman N 4.5 (or

equivalent letters, J-1 of the Jaeger test chart) are separated by 30 cm or more from one eye or both eyes It is

possible to read with.

4.5pt : ace, moon, rose, amuse, care, cross, excuse, wax, zero, measure, curve, news, owner

· The illuminance of the observation surface is 100 footcandles (1000 lux) or more.

· The direct field of view of the observation surface is within 600 mm and within 30 degrees.

6.1 Appearance inspection of cast material

(1) According to JIS G 0588 "Appearance Test Method and Grade Classification of Cast Steel Products Cast

Skin", the types of defects are classified into the following 9 types, classified from 1st grade to 5 grade, and

standard photographs are attached.

1) sand biting, waviness (wart, dent)

2) Gas holes (caught)

3) Casting Flow Line (Wrinkles, etc..)

4) Traces of Keren (trace marks)

5) Gas / gouging sink mark

6) Gas cutting trace

7) Casting

8) Seizure (plugging in, rough skin)

9) Weld marks

Regarding the acceptance criteria, grade is specified for each kind by consultation with the purchaser.

A4 サイズの用紙を使用し、印字した際、横の矢印が 50mm、

縦の矢印が 15mm であることを確認してください。





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(2) In MSS-SP-55 (Visual Method for Evaluation of Surface Irregularities), the types of defects are classified

into the following 12 types, classified as a to e 5 grades, and standard photographs are attached. However,

"a" and "b" are regarded as acceptable and others except those are rejected.

1) Type I-Hot Tears and Cracks

2) Type II-Shrinkages

3) Type III-Sans Inclusions

4) Type IV-Gas Porosity

5) Type V-Veining

6) Type VI-Rat Tails

7) Type VII-Wrinkles, Laps, Folds, and Coldshuts

8) Type VIII-Cutting Marks

9) Type IX-Scabs

10) Type X-Chaplets

11) Type XI-Weld Repair Areas

12) Type XII-Surface Roughness

Note:

Although the above defects include linear defects such as Hot Tears, Cracks, and Shrinkages in the acceptance

range of "a" "b", it is recommended that all linear defects be rejected in the order specification I will.





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The picture below is a picture of defect class "C" extracted from MSS-SP-55-2001. If there are defects beyond

these photographs, they are rejected. However, since the photograph is being reduced, it is necessary to judge

it as a range of 100 mm × 125 mm.

Type-I Hot Tears and Cracks Type-II Shrink Type-III Sand Inclusions

Type-IV Gas Porosity Type-V Veining Type-VI Rat Tails

Type-VII Wrinkles, Laps, Folds

and

Coldshuts

Type-VIII Cutting Marks Type-IX Scabs

Type-X Chaplets Type-XI Welding Repair Areas Type-XII Surface Roughness





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Note)

- Major casting defects and occurrence factors:

(1) Shrinkages

Steel is liquid up to 1500 ° C, when it becomes lower, solidification begins, and solidification is completed

at 1460 ° C.

When the casting temperature is in the range of 1520 to 1560 ° C., the volume shrinkage shrinks by 0.9% by

1460 ° C. and 3% in solidifying.

Shrinkage of 3.9% in total of this liquid shrinkage and solidification shrinkage causes a shrinkage cavity.

· Inadequate casting method

A. Riser's lack of size and height.

B. Lack of distance from “Riser”.

C. “Chill” mismatch.

D. Uneven wall thickness.

E. Lack of molten steel to isolated parts.

· Inadequate work

A. Lack of required molten steel due to leakage of molten steel after completion of casting.

B. Molten steel is short and molten steel does not rise to a predetermined height.

C. The casting speed is too fast and the molten steel that once went up to the height of "Riser" goes down.

D. The height of "Riser" is too high to cause a secondary pipe.

E. In the case of manual work etc., the shape of "Riser" is inappropriate.

F. The curve of the attachment part of "Riser" is too large.

G. The casting temperature is too high or too low.

H. Forget the vent hole with "Blind Riser".

I. The size of "Gate" of "Blind Riser" is inappropriate.

As these major measures,

1) Change the size of "Riser".

2) Change the position and size of "Chill".

3) Effectively use "Side Riser" in addition to "Open Riser".

4) Use sand with high thermal conductivity locally.

5) Correct the position of degassing etc.





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(2) Crack

Cracks can be divided into high temperature cracks and low temperature cracks, but high temperature cracks

are commonly found in castings in general.

High temperature cracks occur at around 1300 ° C, and the main reasons are as follows.

A. The core of the mold, the core, and the core is too strong, there is no stress relaxation, stress concentration

occurs and develops into cracks. There are cases where cracks (HOT TEAR) occurred on the mold splitting

surface.

B. The runner sticks and can not shrink freely.

C. When there is a sudden temperature gradient in that part due to the large wall thickness change.

D. When hot spots (hot spots) are possible.

E. Insufficient deoxidation of molten metal.

F. When there are many P and S in the molten metal.

G. When there are many nonmetallic inclusions in the molten metal.

The portion where cracking occurs is overwhelmingly large at the thick intersection, the part with the most

delayed solidification, and the strain with large strain due to solidification shrinkage.

As a main countermeasure, it is not to make the above cause,

1) Utilization of Chiller and Ribs.

2) Apply flesh to gentle places where wall thickness changes rapidly.

3) Increasing the temperature of the mold and casting etc.

Many cracks open to the surface of the casting film are easy to find.

(3) Gas defect

Gas defects are broadly classified into blow holes and pinholes. This defect is formed by gases melted in the

molten metal, gases and air generated from the mold being confined in the hot water.

The blow hole often absorbs a large amount of gas in the molten metal, and small bore holes of about 2 to 5

φ are distributed on one side. Pinhole is as small as 0.5 ~ 1φ

There are infinite number of gas holes distributed, and after heat treatment, it is often noticeable if it coats

the other layer.

Blowing appears as large cavities by entraining the gas and air in the mold into the hot water.

There are too many factors of gas defects, so measures are also taken for each case, so we will avoid detailed

description.





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(4) Sand Inclusions

It is a defect in which sand of a mold is caught in a casting, it is the easiest to distinguish as a phenomenon,

its cause is also not difficult, but the generation factor is extremely large, which is difficult as a

countermeasure.

As for gas defects, because countermeasures etc. are different in each case, we will avoid detailed description.

6.2 Forging Defects

For each main process of ingot, forging, heat treatment, the surface defects of the forged material and the

main causes of occurrence are shown below. It is recommended that the following defects are not accepted.

1) Incomplete forging penetration:

Dendritic ingot structure at the interior of forging is not broken. Actual forging takes place only at the surface.

Cause- Use of light rapid hammer blows

Remedy- To use forging press for full penetration.

2) Surface cracking:

Cause- Excessive working on the surface and too low temperature.

Remedy- To increase the work temperature

3) Cracking at the flash:

This crack penetrates into the interior after flash is trimmed off.

Cause- Very thin flash

Remedy- Increasing flash thickness, relocating the flash to a less critical region of the forging, hot trimming

and stress relieving.

4) Cold shut (Fold):

Two surfaces of metal fold against each other without welding completely.

Cause- Sharp corner (less fillet), excessive chilling, high friction

Remedy- Increase fillet radius on the die.

5) Unfilled Section (Unfilling/Underfilling):

Some section of die cavity not completely filled by the flowing metal.

Cause- Improper design of the forging die or using forging techniques, less raw material, poor heating.

Remedy- Proper die design, Proper raw material and Proper heating. Figure A- Shows the fish-bone diagram

for root-cause analysis of underfilling defect.

6) Die shift (Mismatch): Misalignment of forging at flash line.

Cause- Misalignment of the die halves.

Remedy- Proper alignment of die halves. Make mistake proofing for proper alignment for eg. provide half

notch on upper and lower die so that at the time of alignment notch will match each other. Figure B- Shows

the fish-bone diagram for root-cause analysis of mismatch defect.





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7) Scale Pits (Pit marks):

Irregular depurations on the surface of forging.

Cause- Improper cleaning of the stock used for forging. The oxide and scale gets embedded into the finish

forging surface.

Remedy- Proper cleaning of the stock prior to forging.

Figure C- Shows the fish-bone diagram for root-cause analysis of Scale Pits defect.

8) Flakes:

These are basically internal ruptures.

Cause- Improper cooling of forging. Rapid cooling causes the exterior to cool quickly causing internal

fractures.

Remedy- Follow proper cooling practices.

9) Improper grain flow:

Cause- Improper die design, which makes the metal not flowing in final interred direction.

Remedy- Proper die design.

10) Residual stresses in forging:

Cause- Inhomogeneous deformation and improper cooling (quenching) of forging.

Remedy- Slow cooling of the forging in a furnace or under ash cover over a period of time.

Figure A: Fish-bone diagram for root-cause analysis of underfilling defect.

Figure B: Fish-bone diagram for root-cause analysis of mismatch defect.





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Figure C: Fish-bone diagram for root-cause analysis of scale pits defect.

Note)

The above content was cited from “International Journal of Scientific and Research Publications, Volume 4,

Issue 6, June 2014”.





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6.3 Visual inspection of welds

Main points are described based on the contents described in ASME B 31.3 - 1993, CHAPTER VI,

INSPECTION, EXAMINATION, AND TESTING.

(1) Types of defects

Cracks

Note1: Weld defect should be judged in combination with nondestructive inspection.

Note2: In ASME B 31.3, the types of defects by VISUAL INSPECTION are described as follows.

Crack, Lack of fusion, Incomplete penetration, Undercutting, Surface porosity or exposed slag inclusion,

Surface finish, Concave root surface & Reinforcement or internal protrusion.





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(2) Judgment criteria (It is not a criterion for non destructive inspection.)

· If cracks and merging defects are observed, they are rejected.

· For other defects, it is stipulated for each service of piping and welding shape.

Please refer to the following table.





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Japan


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6.4 Visual inspection of machined surface

It describes the roughness of the machined surface, especially the contact surface of gasket and packing.

6.4.1 Definition of main roughness standard (JIS B 0601 - 2001 / ISO 4287 - 1997)

(1) Arithmetical mean deviation: Ra

When extracting the portion of the reference length L from the roughness curve and expressing the roughness

curve by Z = f (x) with the average line of the extracted portion as the X axis and the direction of the

longitudinal magnification as the Z axis, It is a value obtained by expression.

That is, in the figure below, the average deviation obtained by dividing the area surrounded by the roughness

curve and the average line by the reference length is shown.





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(2) Maximum height: Ry, Rmax, Rt, Rz, Rzmax, Pt

From the extraction curve Z - f (x), the part of the reference length L (evaluation length) is extracted and the

distance between the summit line and valley line in the extracted part in the longitudinal magnification

direction. The name will change according to calculation standards and extracted curves. In addition, when

the extraction curve is a section curve, it is the value (No. 1) calculated from the whole evaluation length,

and in the case of the roughness curve it is the following three values.

No. 2: Values calculated from the whole evaluation length.

No.3: Value calculated for each reference length, then averaged over the evaluation length.

No.4: Maximum value over the evaluation length after calculation for each reference length.





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For reference:

1) Drawing method of roughness symbol

At present, roughness display by the symbol ▽ is not done, but I will show it for reference.

Center line average roughness Ra according to JIS B 0601 - 1970 is standard.

2) Relationship between machining and roughness

Lathe feed (mm) Actual measurement value

Rmax(μm)

Theoretical value

Rmax (μm)

0.13 3.2 ～ 4.8 3.1

0.25 8.0 11.4

0.40 22.0 29.4

0.50 36.0 45.9

In the above table, reference values were obtained by measuring the roughness by processing the specimen

with a lathe.

Here, the cutting edge radius of the cutting tool was experimented with 0.68 mm.

The theoretical value is Rmax = (f 2/8 r) × 1000, f is the feed (mm) of the lathe per revolution, and r is the

cutting edge radius (mm) of the cutting tool.

3) Roughness symbol

AARH (Average Arithmetic Roughness) In ANSI B 46.1, it is a unit in which the center line average

roughness Ra is expressed in (μin). In addition, RMS: Military Standard and CLA: British Standard are the

same as AARH.





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6.4.2 Roughness of contact surface of gasket and packing

(1) Roughness of gasket contact surface

The roughness of the RF (Raised Face) surface is specified in ASME B 16.5 - 2003 as follows.

Serrated concentric or serrated spiral finish (concentric circle or spiral process), Ra 3.2 to 6.3 μm.

The cutting tool radius of 1.5 mm or more is used, and the turning of the lathe is 1.8 to 2.2 grooves / mm.

For reference:

The roughness is checked by eye and hand feeling using Comparator as shown below.

The photo was quoted from Rubert's website. Rubert's Comparator is used worldwide.





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(2) Roughness of packing contact surface

In API 600-1998, the roughness of the packing contact surface of Stem is specified as Ra 0.80 μm or smoother.

reference:

In Shell-GSI, MESC SPE 77 / 208-2006, Ra 0.2 μm or smoother is stipulated in relation to FE.

However, there are packing makers that are related to FE, even if it is too fine, it will affect the amount of

leakage of FE, so we recommend that you discuss with the valve maker in detail.

For the roughness measurement of the Stem sliding surface, as shown in the

photograph, a roughness measuring instrument is used to slide a fine needle and electrically process it to calculate

roughness.

6.4.3 Flange surface defect Rev.0c

ASME B 16.5-2009 has the following provisions.

The flange surface defects are admitted in the following range.





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6.5 Appearance inspection of coated surface and painted surface

6.5.1 Surface Preparation

(1) rust grade

Sweden standard SIS 05 59 00 - 1967 (equivalent to ISO)

A: Steel surface covered with mill scale adhering to the whole surface, rust has little if any

B: Beginning rust, the steel surface where the mill scale started to peel

C: Although the mill scale has rusted or can be scraped off, the steel surface with indentations that can be seen with the naked eye only slightly

D: The mill scale rusted, and the surface of the steel which remarkably shows the indentation with the naked eye





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(2) Preparation Grades

Standard picture of Sa 2.5 by rust rating according to the Swedish standard SIS 05 59 00 - 1967 (equivalent

to ISO):

A Sa2.5 B Sa2.5 C Sa2.5 D Sa2.5





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6.5.2 Appearance inspection of painted surface (coating film adhesion test method)

Method of diagnosing adhesion on site:

· Tape adhesion test

· Torque adhesion test

· Tensile adhesion test

· Scrape test

Here, we describe the tape adhesion test and the tensile adhesion test (pull-off adhesion test / Elcometer

Adration test) which are used frequently.





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Note:

For coating adhesion test method, it is recommended to determine appropriate conditions and the next term

according to the type and method of painting.

In addition, although problems at the work site are often heard, we recommend that the valve maker and the

ordering party discuss fully with the transportation and storage conditions and period of the valve. In the

order specification sheet, it is possible to prevent the understanding of the valve maker side from being

decided on the ground treatment, the kind and method of painting, the confirmation method of the painted

surface, etc., and so on.


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