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Technical Discussions
saranjee
Engineering, NDT Engineer
Malaysia, Joined Apr 2010, 24

saranjee

Engineering, NDT Engineer
Malaysia,
Joined Apr 2010
24
15:41 May-20-2010
ASME 2235-9

Dear Sir,

I did below calculation according to ASME 2235-9 for thickness 50mm. Please correct me if I am wrong.


1) Surface indication length 30mm, Height 4mm

a) Aspect Ratio = a/l= 4/30 = 0.13

b) a/t = 4/50=0.08



2) Subsurface indication length 25mm, Height 3mm

a) Aspect Ratio = a/2/l= 3/2/25 = 0.06

b) a/2/t = 3/2/50 = 0.03


For all subsurface indication, I divide the height of the indication by 2 and can anyone let me know which sentence mentioning that we need to divide the subsurface indication height by 2 in ASME 2235-9 because I couldn’t find any information about the calculation. Thanks in advance.

 
 Reply 
 
Stan
NDT Inspector,
Canada, Joined Jan 2009, 31

Stan

NDT Inspector,
Canada,
Joined Jan 2009
31
16:06 May-20-2010
Re: ASME 2235-9
In Reply to saranjee at 15:41 May-20-2010 (Opening).

CC2235-9 Fig 1 page 4 gives a diagram showing how to measure defect height for surface and subsurface flaws.
(i)(3)(b) is the clause that defines the use of a and 2a.
Don't forget to read (i)(4)(a) for surface connected flaws, last sentence. A 30 mm long surface connected flaw will not be allowed by any Construction Codes that I can think of.

 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1280

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1280
16:54 May-20-2010
Re: ASME 2235-9
In Reply to saranjee at 15:41 May-20-2010 (Opening).

Sarangee
You have calculated "a". As per the normal protocol of fracture mechanics, the height of a subsurface flaw is 2a. Therefore you would calculate the "a" for the subsurface flaw and then double that value.
If for your surface flaw your a/t is 4/50 then the maximum length allowed is that which makes a/l=0.4 or about 10mm.
For the subsurface flaw 3mm high that means 2a=3mm and "a" is 1.5 so your a/t is 0.03. There is no limit on the aspect ratio here so if it is a recordable indication your limiting factor is 4t. There is no sentence in CC2235 saying to divide by 2 because it is clear from the Figures that the height you measure for the subsurface flaw is twice the value you are to use in the computations.

 
 Reply 
 
Dao Huu Xuan
Other,
Vietnam, Joined Feb 2007, 18

Dao Huu Xuan

Other,
Vietnam,
Joined Feb 2007
18
17:23 May-20-2010
Re: ASME 2235-9
In Reply to saranjee at 15:41 May-20-2010 (Opening).

Dear Saranjee,

As my calculation:

Firstly, we should calculate indication height "a" from given a/t ratio. Second, calculate indication length "l" from a/l ratio. Then you get the indication length in correspondent to the indication height.

This table shows surface flaw acceptance criteria for t=50mm

t a/t Surf a a/l l
50.00 0.031 1.55 0.00 any
0.033 1.65 0.05 33.00
0.036 1.80 0.10 18.00
0.041 2.05 0.15 13.67
0.047 2.35 0.20 11.75
0.055 2.75 0.25 11.00
0.064 3.20 0.30 10.67
0.074 3.70 0.35 10.57
0.083 4.15 0.40 10.38
0.085 4.25 0.45 9.44
0.087 4.35 0.50 8.70

So, if indication height is 4mm, the permitable length is 10.38 mm (lesser of 10.38 and 10.57). And also, if indication length is 30mm, the permitable height is 1.65 mm.
If the indication height 1.55mm or less, then indication is accepted with regardless the length.

For subsurface flaw, calculation also similar:

t a/t Sub a a/l l
50.00 0.034 1.70 0.00 any
0.038 1.90 0.05 38.00
0.043 2.15 0.10 21.50
0.049 2.45 0.15 16.33
0.057 2.85 0.20 14.25
0.066 3.30 0.25 13.20
0.078 3.90 0.30 13.00
0.090 4.50 0.35 12.86
0.105 5.25 0.40 13.13
0.123 6.15 0.45 13.67
0.143 7.15 0.50 14.30


thanks

 
 Reply 
 
saranjee
Engineering, NDT Engineer
Malaysia, Joined Apr 2010, 24

saranjee

Engineering, NDT Engineer
Malaysia,
Joined Apr 2010
24
08:36 May-22-2010
Re: ASME 2235-9
In Reply to Ed Ginzel at 16:54 May-20-2010 .

Dear Sir,

The table 2 only gave us aspect ratio until 0.50. if my aspect ratio more then 0.50 what i should do?Do i need to reject all the indication above 0.50?Did the code case mention anything about this?Thanks for advance.

 
 Reply 
 
Oliviero
NDT Inspector,
Quality Control srl, Italy, Joined Oct 2008, 414

Oliviero

NDT Inspector,
Quality Control srl,
Italy,
Joined Oct 2008
414
13:39 May-22-2010
Re: ASME 2235-9
In Reply to saranjee at 08:36 May-22-2010 .

Dear Saranjee,

the Code Case at point (c) states that "Flaw size shall be not larger than the flaw in Table 1, 2 or 3 for the thickness to be examined".
This means that any flaw with an "a/l" aspect ratio greater than included in Table 2 is rejectable.
This is the formal point of view.

Technically you can reach the same answer thinking to what means an aspect ratio "a/l" 0,50.
Since it means that the flaw is as long as high, we could understand that the flaw is vertically oriented, and vertically oriented could be only a planar flaw.

 
 Reply 
 

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