Miter Bend Calculation

e: Miter Bend Calculation Calculation 08/14/2010 2:22 PM I think you need to use these standards PFI-ES-24 (PFI ES24 - Pipe Bending Methods, Tolerances, Process and Material ) I could be wrong. Bend under internal pressure (841.231): Bend under internal pressure (102.4.5):

Bend under internal pressure (304.2.1):

 pipe under internal pressure pipe under internal pressure where I for intrados is: where I for intrados is:

and I for the extrados is:

and I for the extrados is:

For cold bends the deflection of longitudinal axis and the radius is limited according table in  paragraph 841.231 Hot bends are to be designed and manufactured according ASME B16.49, the internal  pressure rating shall not be less than that which is calculated for straight seamless pipe and the intrados wall thickness should be:

and at sidewall I = 1.0, and at sidewall I = 1.0, R = radius of pipe bend R = radius of pipe bend

Elbows under internal pressure (102.4.5):

Elbows under internal pressure (304.2.1):

where the t the wall thickness of the pipe is

Elbows under internal pressure (841.231?):

Elbows manufactured according standards Elbows manufactured listed in Table 326.1 are suitable for use at according standards listed  No specific design the pressure-temperature ratings specified by in Table 126.1 are suitable rules are listed for

for use at the pressuretemperature ratings specified by such standards.

such standards.

Miter bends under internal pressure (104.3.3):

Miter bends under internal pressure (304.2.3):

fabricated elbows

Elbows not according above standards or for (Does this mean or which design formulas and not given in the allow that an elbow code shall be based on calculations can be calculated Elbows not according consistent with the design criteria of this according a bend with above standards or for code. These calculations shall be uniform thickness? which design formulas and substantiated by one or more of the means Refer B31.3) not given in the code shall stated in A B C or D of 304.7.2, or the elbow  be based on calculations can be calculated according the Bend consistent with the design calculation, refer 304.2.2. criteria of this code. These calculations shall be substantiated by one or more of the means stated in A B C or D of 104.7.2 (Does this mean or allow that an elbow can be calculated according a bend with uniform thickness? Refer B31.3) Miter bends under internal pressure (841.232):

1. When theta =< 22.5 deg than max. allowable pressure shall be the lesser of (t = 1. If system hoop 1. Only straight pipe stress > 40% of T - c): calculations required if: specified minimum yield strength miter  bends are not  permitted. Deflections caused by 2. Pressure shall be limited and misalignment up to 3 to 70 kPa if: deg are not considered as miters. or and thickness is not less than required for straight  pipe 3. Pressure shall be limited to 700 kPa if: and

2. If 10% < hoop 2. When theta > 22.5 deg than max. stress < 40% SMYS allowable pressure shall calculated as (t = T the deflection of each - c): miter shall not exceed 12.5 deg.

For all miter bends the R1 shall not be less

3. If hoop stress < 10% SMYS the total deflection angle shall

than: and thickness is not less than required for straight  pipe with A: 4. For pressure over 700 kPa: proof test, FEA, etc required with a defined minimum for closely spaced and widely spaced miter bend

(T-c) =< 13 mm → A = 25

not exceed 90 deg. 4. If hoop stress > 10% SMYS the distance measured at the crotch shall not be less than one pipe diameter

13 < (T-c) =< 22 mm → A = 2(T-c) (T-c) > 22 mm → A = 2(T-c)/3 + 30

4.04.00 Bends and Elbows i) Elbows shall be generally of long radius type. ii) Bends for piping 65 mm Nb and above shall be made hot and for piping 50 mm Nb and smaller may be made cold. iii) Bends shall be made in accordance with PFI-ES-24. Bends shall be supplied with the minimum tangents except where the piping layout necessitates shorter lengths in which case the tangents shall be suitably reduced after the bending operation to suit the requirements of the piping layout. iv) Heat treatment of bends shall be done as per material specification and PFI-ES-6. v) The finished bends wall thickness at any point of the bend shall not be less than the straight pipe wall thickness. All bends 65 mm Nb and larger shall be ultrasonically examined as per PFI-ES-20. vi) Where examination of bends indicates that wall thinning has resulted in thickness less than the minimum specified, repair by weld deposition shall be allowed only where the length of the affected area is 150 mm or less as measured along the outside arc of the bend. Repairs in excess of this amount shall not be allowed. All repairs shall be carried out only after approval of the Employer.

vii) Circumferential butt welds shall not be used in the area of the bend. Longitudinal welds, where bends are formed from welded pipe shall be located on the bend's neutral axis