PED Hydro test 1.25 x map X WHAT?????

[JAYDEE23]

I am trying to creat a simple excel spreadsheet for my office to use to calculate hydrotest for PED work. We fabricate venturi tubes (so piping).

Per Annex 1 7.4 hydro is no less than
-1.43 x MAP (easy enough)
-1.25 x MAP and MAT

So the consideration of MAT means multiply the ratio for stress between test and design temp right?

Well what figures do we use??

Code of construction allowable stresses (ASME B31.1 in this case)i would think not since PED specifies how to derive allowable stresses.

PED allowable stresses (if so there are many possible ratio's dependent on the method that results in the lower stress value...per Annex 1 7.1

Im lost..some help is appreciated...

 

[JAYDEE23]

I realize my rant may be confusing. In short what figures do I apply the temperature consideration to to get the stress @ room vs the stress @ temp ratio?

 

[JAYDEE23]

Ill tell you what i did to finish the spreadsheet. As PED uses 2/3 yield for allowable stress (in some cases) i used 2/3 yield vs 2/3 yield at temp to get my increaser ratio for hydro....comments?

 

[europipe]

What are you saying?
Are you calculating acc. PED or ASME?
Here is a calculation program for PED
Download software/ped cat. selection.

http://www.stoomwezen.nl/html/downloads.html

 

[Drexl]

Hi,

The proof stress at testing temperature and at TS can be found in the harmonized standards. If you have a material not found in the harmonized standards you need a particular material appraisal.

For pipes, EN 13480-5 gives you the same formula for calculating the test pressure. And the stress values for standard materials can be found in EN 10216 for seamless and EN 10217 for welded pipes.

 

[JAYDEE23]

I use ASME B31.1...my PMA's WPS....etc,etc.....are all approved by my notified body. I do not use harmonized standards.

For hydro pressure i compare all methods from ASME and PED and use the highest.

What figures are compared in the harmonized standards to get the test temp/ vs desing temp ratio multiplier for proof test (hydro)

In ASME allowable stress at temp is derived from a chart. PED has at least 2 approaches (% of yield at temp and % of tensile at temp)

Without doing the actual calculation i do not know which one will result in the lowest and therfore, used, allowable stress. this makes it more difficult for me to make a simple spreadsheet to figure this...

 

[europipe]

Don't think it is the right approach.
When a customer orderes a vessel or pipelinesystem they order acc. ASME or PED.
They want to see calcs acc. one of the two, not 'our calculations are the most safest of the two'

Greetings

 

[JAYDEE23]

I am looking for some explaination on the following when using a code other than the harmonized standards to conform to the PED. ie, ASME... I start with ASME Yields and Tensils, derive my allowable stresses via PED method in 7.1.2,..Where does my stress ratio (test temp / design temp) come from?

ASME?
PED methods?

If PED what figures?
-ASME Yield at test temp / yield at design temp?
-Asme Yield at test temp / 2/3 yield at test temp?





7.4. Hydrostatic test pressure

— that corresponding to the maximum loading to which the pressure equipment may be subject in service taking into account its maximum allowable pressure and its maximum allowable temperature, multiplied by the coefficient 1,25, or

 

[JAYDEE23]

Sorry, corrected to 2/3 yieled at design....

if PED what figures?
-ASME Yield at test temp / yield at design temp?
-Asme Yield at test temp / 2/3 yield at DESIGN temp?

 

[europipe]

I think you better consult a material engineer.
And when you built systems acc. B31.3 then you can find all yieldstresses there.

 

[JAYDEE23]

hmmmm?

no materials engineer necessary. Simple question... Where does PED intend the ratio come from when they say

"taking into account its maximum allowable pressure and its maximum allowable temperature"

Your responses are things that are are obvious. Do you not understand what i am asking?

Someone with experience with ASME/PED could answer my question perhaps?

 

[europipe]

Just like Drexl says, you can find it in the appropriate EN and ASME standards.
Ped has no strenght calculations itself.

 

[Drexl]

Hi,

The ratio is f,test / f and both are both are calculated according to PED Anx 1, 7.1.2.

Example P235GH, TS = 350 degC, PS = 9 barg, Test temp = 20 degC

Rm/20 = 360 N/mm2
Rp0.2/20 = 235 N/mm2
Rp0.2/TS = 120 N/mm2

f,test = min(2/3 * R0.2/20, 5/12 Rm/20) = min(156.7 , 150) = 150 N/mm2
f = min(2/3 * R0.2/TS, 5/12 Rm/20) = min(80 , 150) = 80 N/mm2

PT = 1.25*PS*f,test/f = 1.25*9barg*150/80 = 21.09 barg

 

[JAYDEE23]

Thank you Drexl...that clears it up and is as i suspected...