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Pipe Wall Thickness Calculation - EN 13480 Part 3

Pavan Kumar

Chemical
Aug 27, 2019
375
Hi All,

I have assigned to check the design pressure of a Welded Carbon Steel Pipe (EN 10217-2 Gr P235GH or EN 1.0345) for DN 400 (OD= 406.4mm) line size with a wall thickness of 11mm. The fluid is Saturated Steam at 16 bar(g) ( TSat= 204.345 Deg C). I went through EN 13480 Part -3 and got the formula for Pipe Wall Thickness without any allowances or tolerances.

e =( pc * Do ) / (2* f*z+pc) ------> From EN 13480-3 : 2002+A4

where,
e = pipe minimum wall thickness, mm
pc - calculation pressure or Design Pressure, N/mm2
Do - Pipe OD ,mm
f - Design stress or allowable stress, N/mm2
z - joint coefficient ( z=1 for seamless pipes)

Going through EN13480-3, I see that f needs to calculated as the lower of Time Independent and Time Dependent stress. This calls for determining values such ReH,t, Rp,0.2,t, Rm etc. I need help on how to get these values. Also I need help to determine the Time dependent stress fCR = SRT,t/ SFCR. How do I get SRT, t?

Any guidance will be very helpful to me.

Thanks and Regards,
Pavan Kumar
 
Last edited:
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Pavan,

You know better than to have duplicate posts. See the one in chemical forum.
 
Pavan,

You know better than to have duplicate posts. See the one in chemical forum.
Hi LI,

Sorry, but I could not get the information that I wanted so I posted it here. I apologize for that. This seems to be the correct forum for this question.

Thanks and Regards,
Pavan Kumar
 
Hi Hubert (XL83NL),

I tried to calculate the Design pressure of EN 10217-2 Gr P235GH material (EN 1.0345) for DN 400 pipe using EN 13480 Part-3. I used the below data and I got a very low design pressure value. I did the same calculation in ASME B31.1 for ASTM Equivalent Material and got much much higher values. I want to seek your help to understand what is the correct way to do this calculation.

1. Pipe OD, Do=406.4mm
2. Pipe Wall Thickness, e-ordered = 11 mm
3. Corrosion Allowance, Co = 1.5875mm ( assumed 1/16" Corrision Allowance)
4. Under Tolerance Allowance = 1.375 mm ( Assumed 12.5% of Wall Thickness as Under Tolerance Value)
5. Thinning Allowance , C2= 0 mm ( Assumed no thinning as it is a straight pipe)
6. E = Additional Thickness from selection of Ordered Thickness = 1 mm ( Assumed, Not sure where to get this from).

e-ordered = e + E + Co+C1+C2

e = Minimum Pipe Wall Thickness for Internal Pressure without any allowances or Tolerances = e-Ordered-E-Co-C1-C2 = 11-1-1.5875-1.375 = 7.0375mm

Time-Independent Stress:

With EN 10217-2 being not austenitic steel, I used formula 5.2.1-1 and Table 4 of Material Standard 10217-2.

ReH = 235 MPa at Room Temperature
RP0.2t = 168 MPa at Design Temperature of 204.345 Deg C ( Obtained through interpolation of Rp0.2,t = 170 MPa at 200 Deg C and =150 MPa at 250 Deg C)
Rm= 360 MPa (Took the minimum value of the range 360-500 MPa)

f = Min{ ReH/1.5 , Rp0.2t/1.5 , Rm/2.4}

f = Min(235/1.5,168/1.5, 360/2.4) = 112 MPa = 112 N/mm2

Time-Dependent Stress:

Could not find any table or value for SRT,t in the material standard EN 10217-2, so ignored it

so,

Pipe Design Pressure Calculation:

f = 112 N/mm2
Z= 0.85 ( Joint Efficiency Coefficient for Welded Pipes)
e = 7.0375 mm
Do=406.4 mm

e = pc . Do / (2fZ+pc)

or pc = (2fz+e)/(Do-e)

substituting above values,

pc =( 2*112*0.85 + 7.0375)/ (406.4-7.0375) = 0.494 N/mm2 = 0.49 MPa = 4.9 bar(a).

Comparing with ASME B31.1 calculation this value is too tow. I got 43.7 bar(g) per ASME B31.1 (2020 Edn).

Please see my spreadsheet attached.

Thanks and Regards,
Pavan Kumar
 

Attachments

  • 601.3 and 601.4 - Pipe Design Pressure Calculation.xlsx
    55.3 KB · Views: 2
There's something wrong with your equation change when you go from e = .... to Po =

This bit is wrong.

e = pc . Do / (2fZ+pc)

or pc = (2fz+e)/(Do-e)

If you go back to the original equation and find thickness for say 4 Mpa, and 112MPa you get 7mm. I can't follow that algebra.
 
There's something wrong with your equation change when you go from e = .... to Po =

This bit is wrong.

e = pc . Do / (2fZ+pc)

or pc = (2fz+e)/(Do-e)

If you go back to the original equation and find thickness for say 4 Mpa, and 112MPa you get 7mm. I can't follow that algebra.
HI LI,

Yes I made a silly re-arrangement mistake. The correct eqn is pc = 2efZ/(Do-e)

This gives me pc= 2*7.0375*112*0.85/(406.4-7.0375) = 3.3 N/mm2 = 33.5 bar(a)=33.5-1.01325=32.4 bar(g).

But still this way lower than 44 bar(g) which I calculate from ASME B31.1.

Thanks and Regards,
Pavan Kumar
 

Attachments

  • 601.3 and 601.4 - Pipe Design Pressure Calculation.xlsx
    55.7 KB · Views: 1
This is an interesting document


Why do you think the amassed is bara?

Does 31.1 have the Z factor?
Hi LI,

What does amassed mean?. Are you asking my I got the design pressure in bar(a)?. If so EN 13480 Part 3 did not say it was bar(g) or bar(a) so I assumed it be bar(a).

What does Z factor mean?. You mean Joint Efficiency coefficient. If so, Yes it does it is called Weld Joint Efficiency Factorn "W".

Thanks and Regards,
Pavan Kumar.
 
Hi LI,

What does amassed mean?. Are you asking my I got the design pressure in bar(a)?. If so EN 13480 Part 3 did not say it was bar(g) or bar(a) so I assumed it be bar(a).

What does Z factor mean?. You mean Joint Efficiency coefficient. If so, Yes it does it is called Weld Joint Efficiency Factorn "W".

Thanks and Regards,
Pavan Kumar.
Sorry - typo I didn't notice. should have been "answer"

The ONLY people who think that pressure is by default bara are process engineers. Everyone else uses bar to mean barg and KPa to mean KPag. Only if it is bara does anyone actually say bara....

If you've got differences between 31.1 and EN 13480, you need to look closely at the input values, especially the value of S. If you have different allowable stress numbers between the two codes, you're going to get different answers.

But your answer is still more than 16 bar, so what's the problem?
 
Sorry - typo I didn't notice. should have been "answer"

The ONLY people who think that pressure is by default bara are process engineers. Everyone else uses bar to mean barg and KPa to mean KPag. Only if it is bara does anyone actually say bara....

If you've got differences between 31.1 and EN 13480, you need to look closely at the input values, especially the value of S. If you have different allowable stress numbers between the two codes, you're going to get different answers.

But your answer is still more than 16 bar, so what's the problem?
Hi Li,

My calculations has a lot of assumptions and I could not locate Creep Stress value. So my answer is to be confirmed. I contacted Hubert(XL83NL) on Linkedin and he said he will get back end of this week.

Thanks and Regards,
Pavan Kumar
 
Hi Hubert (XL83NL),

I tried to calculate the Design pressure of EN 10217-2 Gr P235GH material (EN 1.0345) for DN 400 pipe using EN 13480 Part-3. I used the below data and I got a very low design pressure value. I did the same calculation in ASME B31.1 for ASTM Equivalent Material and got much much higher values. I want to seek your help to understand what is the correct way to do this calculation.

1. Pipe OD, Do=406.4mm
2. Pipe Wall Thickness, e-ordered = 11 mm
3. Corrosion Allowance, Co = 1.5875mm ( assumed 1/16" Corrision Allowance)
4. Under Tolerance Allowance = 1.375 mm ( Assumed 12.5% of Wall Thickness as Under Tolerance Value)
5. Thinning Allowance , C2= 0 mm ( Assumed no thinning as it is a straight pipe)
6. E = Additional Thickness from selection of Ordered Thickness = 1 mm ( Assumed, Not sure where to get this from).

e-ordered = e + E + Co+C1+C2

e = Minimum Pipe Wall Thickness for Internal Pressure without any allowances or Tolerances = e-Ordered-E-Co-C1-C2 = 11-1-1.5875-1.375 = 7.0375mm

Time-Independent Stress:

With EN 10217-2 being not austenitic steel, I used formula 5.2.1-1 and Table 4 of Material Standard 10217-2.

ReH = 235 MPa at Room Temperature
RP0.2t = 168 MPa at Design Temperature of 204.345 Deg C ( Obtained through interpolation of Rp0.2,t = 170 MPa at 200 Deg C and =150 MPa at 250 Deg C)
Rm= 360 MPa (Took the minimum value of the range 360-500 MPa)

f = Min{ ReH/1.5 , Rp0.2t/1.5 , Rm/2.4}

f = Min(235/1.5,168/1.5, 360/2.4) = 112 MPa = 112 N/mm2

Time-Dependent Stress:

Could not find any table or value for SRT,t in the material standard EN 10217-2, so ignored it

so,

Pipe Design Pressure Calculation:

f = 112 N/mm2
Z= 0.85 ( Joint Efficiency Coefficient for Welded Pipes)
e = 7.0375 mm
Do=406.4 mm

e = pc . Do / (2fZ+pc)

or pc = (2fz+e)/(Do-e)

substituting above values,

pc =( 2*112*0.85 + 7.0375)/ (406.4-7.0375) = 0.494 N/mm2 = 0.49 MPa = 4.9 bar(a).

Comparing with ASME B31.1 calculation this value is too tow. I got 43.7 bar(g) per ASME B31.1 (2020 Edn).

Please see my spreadsheet attached.

Thanks and Regards,
Pavan Kumar
Hi All,

I have assigned to check the design pressure of a Welded Carbon Steel Pipe (EN 10217-2 Gr P235GH or EN 1.0345) for DN 400 (OD= 406.4mm) line size with a wall thickness of 11mm. The fluid is Saturated Steam at 16 bar(g) ( TSat= 204.345 Deg C). I went through EN 13480 Part -3 and got the formula for Pipe Wall Thickness without any allowances or tolerances.

e =( pc * Do ) / (2* f*z+pc) ------> From EN 13480-3 : 2002+A4

where,
e = pipe minimum wall thickness, mm
pc - calculation pressure or Design Pressure, N/mm2
Do - Pipe OD ,mm
f - Design stress or allowable stress, N/mm2
z - joint coefficient ( z=1 for seamless pipes)

Going through EN13480-3, I see that f needs to calculated as the lower of Time Independent and Time Dependent stress. This calls for determining values such ReH,t, Rp,0.2,t, Rm etc. I need help on how to get these values. Also I need help to determine the Time dependent stress fCR = SRT,t/ SFCR. How do I get SRT, t?

Any guidance will be very helpful to me.

Thanks and Regards,
Pavan Kumar
Why do you even have to do the time-dependent evaluation? CS @204 C will never cross to the creep regime. Temperature limit to define the creep range for EN 10217-2 Gr P235GH material will be 343C-371C depending on the reported tensile strength.
 
Why do you even have to do the time-dependent evaluation? CS @204 C will never cross to the creep regime. Temperature limit to define the creep range for EN 10217-2 Gr P235GH material will be 343C-371C depending on the reported tensile strength.
HI GD2,

I am not well versed with terms like Creep and mechanical properties of materials and want to know how you established the Creep range for EN 10217-2 P235GH material as 343-371 Deg C?. If the Creep stress can be neglected and then could you go through my calculations and let me know if the Upper yield strength at room temperature(ReH,t), minimum specified value at 0.2% proof strength(Rp0.2,t) and tensile strength at room temperature (Rm) that I have taken are correct for this material.

Thanks and Regards,
Pavan Kumar
 

Attachments

  • 601.3 and 601.4 - Pipe Design Pressure Calculation.xlsx
    55.7 KB · Views: 0
HI GD2,

I am not well versed with terms like Creep and mechanical properties of materials and want to know how you established the Creep range for EN 10217-2 P235GH material as 343-371 Deg C?. If the Creep stress can be neglected and then could you go through my calculations and let me know if the Upper yield strength at room temperature(ReH,t), minimum specified value at 0.2% proof strength(Rp0.2,t) and tensile strength at room temperature (Rm) that I have taken are correct for this material.

Thanks and Regards,
Pavan Kumar
Sorry, I am not used to EN standard. I am an ASME guy. I can’t therefore validate your strength numbers.
As for creep, it is when the material time-dependent properties kicks-in. Examples are heater tubes where the tubes has to be designed for both elastic and rupture (creep).
If you haven’t heard creep, you are far away from mechanical engineering knowledge base that you need to work on.
 

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