Calculation of stresses should take into account circumferential, longitudinal, shear and equivalent stresses.

-Calculations should also take into consideration stress intensification factors that normally occur in components.

Calculation of stresses in loops, bends and offsets should be based on total range from min to max temperature normally expected.

**STRESS FROM INTERNAL PRESSURE**

It is calculated as:

where:

*D* = outside diameter of pipe, in. (mm)

*P*_{i }= internal design gage pressure, psi (bar)

*S _{H}* = circumferential (hoop) stress due to internal pressure, psi (MPa)

*t *= wall thickness of pipe, in. (mm)

**STRESS FROM EXTERNAL PRESSURE**

It is calculated as:

where:

*D* = outside diameter of pipe, in. (mm)

*P _{e}* = external design gage pressure, psi (bar)

*S _{H}* = circumferential (hoop) stress due to external pressure, psi (MPa)

*t* = wall thickness of pipe, in. (mm)

This code recognizes two restraint conditions:

**“Restrained” pipelines**

-Sections of buried pipe.

-Above ground pipe sections attached to supports.

-Field bends in and adjacent pipe buried in stiff or consolidated soil.

**“Unrestrained” pipelines**

-Above ground pipe configured to accommodate thermal expansion.

-Field bends and adjacent pipe buried in soft or unconsolidated soil.

:: ASCE Guidelines for the Design of Buried Pipelines: **www.asce.org**

**STRESS FROM THERMAL EXPANSION**

It is calculated as:

**Restrained pipe:**

where:

*E* = Modulus of Elasticity

*S _{E}* = thermal expansion stress, psi (MPE)

*T _{1}* = Temperature at installation or completion of final tie-in,

^{0}F (

^{0}C)

*T _{2} *= operation temperature,

^{0}F (

^{0}C)

a = coefficient of thermal expansion, in./in./^{0}F (mm/mm/^{0}C)

**STRESS FROM THERMAL EXPANSION **

It is calculated as:

**Unrestrained pipe:**

where:

*S _{b}* = resultant bending stress, psi (MPa)

*S _{t}* = torsional stress, psi (MPa)

*S _{b}* is calculated as:

where:

*i _{i}* = in-plane stress intensification factor. Note that

*i*, is 1 for pipe.

_{i}*i _{o}* = out-of-plane stress intensification factor. Note that

*i*is 1 for pipe.

_{o}*M _{i}* = in-plane bending moment, in-Ib (Nm)

*M _{o}* = in-plane bending moment, in-Ib (Nm)

*Z* = Section modulus of the pipe or of the fitting outlet, in^{3} (cm^{3})

*S _{t} *is calculated as:

where:

*M _{t}* = torsional moment, in.-Ib (Nm)

where:

*M _{t}* = Torsional moment

*M _{i}* = In plane bending moment

*M _{o}* = Out of plane bending moment

**Credit text:** Tuan Muhammad Hafizul

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**Tarikh**: 18 Disember 2021

**Hari**: Sabtu

**Masa**: 9.00 pagi – 4.30 petang

**Platform**: Zoom

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