bend tolerances 2

7/31/2019 Bend Tolerances 2

1/15

PIPE 3D- PROJECTIONS

The line parallel to the respective axis is the direction of the bend. So is

the direction of the branches coming on those pipes.

Y-axis

X-axis

Z-axis

20


2/15

FACE OUT

Pipe face out -1mm max.for GTAW and

3.0mm for other joints

Flange face out -1.0mm per 25mm or

1.0mm whichever is greater

Rotation of flanges from the indicated

position-2.0mm max.


3/15

BEND ANGLE

Reference

Bend Angle 0.5 deg. -Acceptable


4/15

WRINKLES

1. The depth of valley / OD (d/D) shall be < or = 3%2. Pitch of valley / Depth (A/d) shall be > or = 12

3. Wrinkles beyond acceptable limits shall be corrected. Alloy steel

pipes shall be checked by LPI/MPI after correction.

Depth d=(D1+D2)/2-D3


5/15

OVALITY

1. IBR: < or = 20D/R

2. ANSI: 8% max. for bends of R/D > 5

Where R= Radius of bend & D = Diameter of the Pipe

% of Ovality = {(Dmax Dmin)/ D nominal }x 100

Dnominal

Dmax

Dmin


6/15

LINEAR DIMENSIONS

Tolerance on straight portionencompassing bends : 10mm

Tolerance on straight portion for endlimbs of multiplane bends : + 15/-5mm

Bend Radius:5.0mm


7/15

NOZZLE LOCATIONS ON PIPES

Pitch and Height

Upto OD 273mm- 3.0mm

From OD 323.9mm to 609.6mm -5.0mm

From OD 609.6mm to OD 914mm

Over OD 914-6.0mm+2.0mm for each 305mm increasein OD

Circumferential shifting-3.0mm.However maintainverticality.Face out shall be within the limits.


8/15

TOLERANCE FOR BENDS

a) For single Offset & single plane bends 5 mm 5 mm

b) For Compound Offset/ Multi plane bends: 10 mm

10 mm

10 mm


9/15

U-SHAPED BENDS

10 mm


10/15

PIPE LENGTH

Arm Length: +5/-2mm

Pipe Length(DC pipes):+3/-1mm

Other pipes:+/-3mm


11/15

U-SHAPED BENDS (Cont.0

5 mm


12/15

STRAIGHTNESS

Tolerance on Pipe Straightness

For every one meter length 1 mm bow is acceptable

Overall bow shall not be more than 6 mm over the

entire length


13/15

90 BEND

Tangent

Tangent R

Tangent = R x tan 2

Diagonal = 2R


14/15

OTHER THAN 90BEND

Tangent

Tangent

R

Diagonal

Tangent = R x tan2

Diagonal = 2R x sin 2


15/15

List of tools required to mark and check the bends

1)Combination set -2 nos.2)Channel spirit level -2 nos.3)Protractor -2 nos.4)Straight edge 5 metres -2nos.5)Straight edge 3 metres -2 nos.6)Straight edge 2 metres -2 nos.7)1 lb.Hammer -2 nos.8)2 lb.Hammer - 2nos.9)30M measuring tape -2 nos.10)3M measuring tape -2 nos.

11)Centre Punch -2 nos.12)Number punch(0 to 9) -2 set13)Letter punch (A to Z) -2 sets14)Marking Table 5M x 5M -1 No.15)300mm Try square -2 nos.16) Marking Scriber -2 nos.17) Marking pencil -2 nos.18) Plumb set -2 nos.19)Twine20) Piano wire -1 bundle

bend tolerances 2

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