Subsize Specimen(Asme VIIITable UG-84.2 ,Asme B31.3 Table 323.3.4, AWS D1.1 Table 4.15 )

[WE17]

Hi Everyone,

I have question regarding Subsize Specimen (Asme VIIITable UG-84.2 ,Asme B31.3 Table 323.3.4, AWS D1.1 Table 4.15 )But for now Just concentration for ASME VIII div 1 Table UG-84.2 and See UG-84(c)(5)(b).
First Question :
1. I have PQR 6 inch, schedule 40 pipe (168.3mm outside diameter x 7.11mm wall thickness)so what is Temperature Reduction and Thickness Reduction ???

By seeing note in Table UG-84.2 note below said : Stright Line Interpolation for intermediate values is permitted ?
SO are you agree if :
a. Temperature Reduction is (by stright line interpolation): ((7-7.11)/(7-7.5)=(4-x)/(4-3)) result is 3.78 deg C
Let say MDMT is -40 deg C so Impact doing in -43.78 deg C ?
or
We need aware of 80% of nominal thk. so calculation max thk I can use 5mm THK so :
THK 5 = 11, THK 7 = 4 means 11-4=7 deg C , Let say MDMT -40 so test temperature -47 deg C ?

b. Thickness Reduction (Let say acceptance criteria 27 Joule) is by stright line interpolation): result is 19.197
so acceptance beeing 19.197 joule instead 27 Joule ?

Please anyone who interesting with this case to help me understanding the interprestation ? Thankyou for valuable advice


we 17


Thanks n Regards

 

[weldstan]

The temperatuire reduction only applies when the thickness of the Charpy specimen is less than 80% of the thickness of the base/weld metal. A Charpy specimen, 5.6 mm thick or thicker will not require a temperature reduction.

 

[WE17]

Hi Weldstan,

By first looking your statement made me confused, But after recheck with the code you completely open the key. UG 84 (c) 5 b Paragraph one
said if your nominal thk not less than 80% so no need temp. reduction and Paragraph 2 said that if less than 80% so need temperature reduction.
So even my PQR thk 7.11 no need temperature reduction ?But if me doing machine to thk 5mm so i need temp reduction ? am i correct ?

if you still want help me please kindly help to answer below ?
1. But what is the purpose to do machining 7.11 to 5 mm thk? why just impact it at 7.11 mm thk ?
2. This one Correct : my first question
" We need aware of 80% of nominal thk. so calculation max thk I can use 5mm THK so :
THK 5 = 11, THK 7 = 4 means 11-4=7 deg C , Let say MDMT -40 so test temperature -47 deg C ?"

Thankyou for Valuable answer Weldstan...I hope God always bless you

Thanks n Regards

We 17

 

[weldstan]

When qualifying the WPS on small diameter, thin wall pipe, it is often difficult or impossible to machine the Charpy specimen to the same thickness of the pipe. When the specimen thickness is less than 80% of the thickness, the Code mandates the temperature decrease. This is required for a number of reasons; e.g., the effect of geometry on test, as thickness becomes very small, fracture will be in shear mode - not cleavage.

 

[WE17]

Hi Weldstan,

Thankyou for your valuable advice,You Open my mind. by the way Regarding my calculation(stright line calculation for reduction temperature and acceptance) above is it correct ?

Thanks n Regards

We 17