Working pressure calculation for elbows
1. Standard
Calculation is performed according to regulated formulas and stress values. The Standards defines the grades and their required Design stress.
2. Grade
Different grades have different design stress, selection of grades have impact on the dimensioning of the pipe system. Basis for the selection of grade should be corrosive environment, strength, durability, high temp requirements and cost.
3. Temperature
Select the maximum design temperature for the application.
4. Joint factor
The joint factor (z or Ej) for the longitudinal weld is regulated in the design standards. Z/Ej=1.0 is achieved with 100% Eddy Current or 100% Radiographic testing. This means that the strength of the weld is equal to that of the base material. Welded pipes delivered to EN 10217-7 have a weld factor of 1.0. ASTM-pipes must be 100% X-rayed to get Ej=1.0.
5. Diameter
The outer diameter of the elbow
6. Radius
The radius of the elbow, to the center of the elbow
7. Pressure requirement
Set the maximum design pressure for your application.
7. Thickness requirement
Set the maximum design thickness for your application.
Calculation basis
The calculation is made using formula B.4.2-2 in EN 13480-3 Annex B
For standard EN10253-3 the following applies:
for equipment not subject to non-destructive testing other than visual inspection : 0,7
for equipment subject to random non-destructive testing : 0,85
For standard EN10253-4 the following applies:
Following methods of examination can be used for fittings according to EN10253-4 (Z=1,0)
- "radiographic examination"
- "eddy current examination for fittings with wall thickness not greater than 6 mm"
- "ultrasonic examination"
Disclaimers
This calculation tool is intended as a useful guide in
calculating the sizes for OSTP welded elbows of
certain grades and sizes.
However results obtained should be regarded as rough indications only.
Dimensioning of pipe systems is also dependant on external forces, thermal
stress, static weight etc.