PROCESS & PIPING DESIGN SECTION

MECON LIMITED
DELHI - 110 092

TECHNICAL SPECIFICATION
FOR
LONG RADIUS BENDS

SPECIFICATION NO. : MEC/TS/05/62/015, Rev-1

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 MECON LIMITED PROCESS & PIPING STANDARD SPECIFICATION
DELHI DESIGN SECTION

TITLE LONG RADIUS BENDS SPECIFICATION NO. PAGE 1 OF 8

MEC/TS/05/62/015 REVISION 1

CONTENTS

1.0 SCOPE

2.0 REFERENCE DOCUMENTS

3.0 MATERIAL

4.0 MANUFACTURE

5.0 INSPECTION AND TESTS

6.0 MARKING, PACKING AND SHIPMENT

7.0 WARRANTY

8.0 DOCUMENTATION

Revision No. Date Revised by Checked by Approved by

PREPARED BY : CHECKED BY : APPROVED BY :

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TITLE LONG RADIUS BENDS SPECIFICATION NO. PAGE 2 OF 8

MEC/TS/05/62/015 REVISION 1

1.0 SCOPE

This specification covers long radius steel pipe bends to be manufactured in

accordance with the requirements of MSS-SP (Manufacturers Standardisation
Society – Standard Practice) – 75, latest edition, to be used in pipeline system
handling Natural Gas. The selection of options permitted by MSS-SP-75 shall be
as described below. All applicable requirements contained in the MSS-SP-75
shall be fully valid unless cancelled, replaced or amended by more
requirements as stated in this specification. In case of conflict between the
requirements of this specification and MSS-SP-75, the requirements of this
specification shall govern.

2.0 REFERENCE DOCUMENTS

Reference has also been made in this specification to the latest edition of the
following codes, standards and specifications.

a) ANSI B31.8 : Gas Transmission and Distribution Piping

System.

b) ASME – Sec. VIII : Boiler and Pressure Vessel Code

Div. 1

c) ASME – Sec IX : Boiler & Pressure Vessel Code

Welding and Brazing Qualifications

d) API Spec. 5L : Line Pipe

e) ASTM Part-I : Steel – Piping, Tubing, Fittings

In case of conflict between the above reference documents and this

specification, the requirements of the specification shall prevail.

3.0 MATERIALS

3.1 Bends shall be fabricated from bare steel line pipe (to be issued as free issue
item by Purchaser). The details of free issue line pipe material is given
separately in LR Bend Data Sheet & Purchase Requisition.

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TITLE LONG RADIUS BENDS SPECIFICATION NO. PAGE 3 OF 8

MEC/TS/05/62/015 REVISION 1

3.2 All mechanical properties of the bends after finishing shall be same as pipe
specification as referred in section 3.1. The following tests shall be conducted
on finished bends and test procedures shall be as per pipe specification as
referred in para 3.1.

3.2.1 One transverse tensile test will be conducted to establish the yield strength,
ultimate tensile strength and elongation of :

a) Base material at inside radius of the bend.

b) Base material at outside radius of the bend.

3.2.2 One all weld tensile test will be conducted (wherever applicable) to establish
yield strength, ultimate tensile strength and elongation of weld material on
bend.

3.2.3 Three transverse Charpy-V-notch impact tests shall be conducted on full sized
specimen of the same heat in accordance with ASTM A370 at 0°C for each of
the following :

a) Base material at outside radius of the bend.

b) Weld material of bend

3.2.4 Guided Bend Tests

One face and one root guided bend weld test shall be performed on samples
cut from one bend per heat of steel. The dimensions `A’ in guided bend test
shall not exceed 4.0 times the nominal wall thickness and dimension `B’ shall
be equal to A + 2t + 3.2mm.

4.0 MANUFACTURE

4.1 Bends shall be manufactured by hot bending of pipe applying induction heating
only.

The adopted procedure shall be completed by suitable heat treatment to

achieve the required mechanical and chemical properties of the finished bends
and is accepted only after written approval of the Purchaser. The procedure
shall ensure uniform bending without any defects other than those allowed in
this specification and pipe specification as referred in para 3.1.

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 MECON LIMITED PROCESS & PIPING STANDARD SPECIFICATION
DELHI DESIGN SECTION

TITLE LONG RADIUS BENDS SPECIFICATION NO. PAGE 4 OF 8

MEC/TS/05/62/015 REVISION 1
4.2 When bending, the weld wherever applicable shall be located at approx. 10° from
the neutral zone, measured at outside of the bend as indicated in figure below.
10°

W E LD H ER E B E N D IN G P L A N E
OR
HERE

BEND

10°

4.3 Bevels at the ends shall be as specified in MSS-SP-75 unless otherwise specified
differently in the material/ purchase requisition.

4.4 Bends shall not have any circumferential joint.

4.5 No repair by welding is allowed on any part of the bends.

4.6 The cooling of the bend immediately after bending shall be an interval cooling,
alternatively with water and air at a minimum pressure of 2 atmospheres.

4.7 The procedure shall be such which shall not require any additional heat –
treatment after bending. If such a heat treatment is required, it is permitted only
after the written approval of purchaser and shall be carried out at Manufacturer’s
expense.

4.8 Bulges, dents and flat areas shall not appear within 100mm from end of the bend.

For the remaining part of the bend these deviations from the original contour of
the pipe are permitted but the same shall be repaired, provided these deviations
shall not exceed 6.5% of nominal wall thickness in height/ depth and the same
shall not extend (in any direction) over a distance of more than 25% of nominal
diameter.

4.9 The excess weld material wherever applicable at the inside of the bend shall be
removed over a distance of 100mm at both ends.

4.10 Tolerances
The dimensions of bends shall be controlled to make sure that they are
manufactured according to the tolerances indicated below over and above the
requirements of MSS-SP-75

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DELHI DESIGN SECTION

TITLE LONG RADIUS BENDS SPECIFICATION NO. PAGE 5 OF 8

MEC/TS/05/62/015 REVISION 1
4.10.1 Minimum Inside Diameter : -2.5% of inside nominal
diameter except 200mm from ends

Bend Angle : ±1°

Bend Radius : ± 1% of bending nominal

Diameter

4.10.2 The manufacturer shall check the wall thickness of the pipe before and after
bending along the outside radius either at distances approximately equal to
pipe diameter or 300mm whichever is less. The measured wall thickness shall
be atleast equal to :

tmin = 0.95 (tnom. - t)

tnom = nominal wall thickness as specified in the

material/ purchase requisition.

t = 0.35mm for a wall thickness smaller than

10mm.
t = 0.50mm for a wall thickness 10mm or more.

4.10.3 Ovality may be defined as :

OD max. – OD min
OD nom.

The above value shall be < 1% within 100mm from each end and < 6% for
remaining part of the bend. The measurement shall be made over the
circumference of the bend either at distance approximately equal to pipe
diameter or 300mm whichever is less.

4.10.4 Wrinkles

Measurements of the outside diameter shall be taken in the plane of the bend
at locations where wrinkles are present (OD max.) and at locations where
wrinkles are not present (OD min,). The acceptance limit shall be as defined
below.
OD max. – OD min
------------------------- < 1%
OD nom.

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TITLE LONG RADIUS BENDS SPECIFICATION NO. PAGE 6 OF 8

MEC/TS/05/62/015 REVISION 1

5.0 INSPECTION AND TESTS

5.1 The manufacturer shall perform all inspection and tests as per the
requirements of this specification and MSS-SP-75 prior to shipment at his
works. Such inspection and tests shall be, but not limited to, the following :

a) Verify that the unfinished product arriving at manufacturer’s shop is in

full compliance with the pipe specification as referred in para 3.1.
b) Visual Inspection.
c) Dimensional and tolerances check as per MSS-SP-75 and requirements
of section 4.0 of this specification.
d) Check heat treatment, if carried out, as required and maintain its
records.
e) Temperature against time recorder charts for each induction heating.
f) Material properties shall be checked to meet the requirements of section
3.0 of this specification.
g) The non-destructive inspection on the finished bend shall be carried out
as given below :

All longitudinal seam welds shall be fully radiographed and

acceptance limits shall be as per pipe specification as referred in
para 3.1.
The full circumference of both ends of each bend after bevelling
shall be ultrasonically tested for laminations over a length of 25mm
and acceptance limits shall be as per pipe specification as referred in
para 3.1.

5.2 Purchaser’s Representative reserves the right to perform stagewise inspection

and witness tests on all bends as indicated in para 5.1 at Manufacturer’s
works, prior to shipment.

Manufacturer shall give reasonable notice of time and shall provide without
charge reasonable access and facilities required for inspection, to the
Purchaser’s Representative. Inspection and test performed or witnessed by
Purchaser’s Representative shall in no way relieve the Manufacturer’s
obligation to perform the required inspection and tests. Under no
circumstances any action of the Purchaser’s Representative shall relieve the
Manufacturer of his responsibility for the material, design, quality and
operation of the equipment.

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 MECON LIMITED PROCESS & PIPING STANDARD SPECIFICATION
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TITLE LONG RADIUS BENDS SPECIFICATION NO. PAGE 7 OF 8

MEC/TS/05/62/015 REVISION 1

5.3 Test Certificates

The Manufacturer shall produce the Certificates (in original) for all, but not
limited to, the following :

a) Certificates of chemical analysis and mechanical tests carried out on

pipe and bends separately.

b) Certificates of required non-destructive test inspection.

c) Certificates of heat treatments, if any.

d) Certificates of all other tests as required in this specification.

In case any of the above said certificates are not available during the final
inspection, the supply shall be considered incomplete.

6.0 MARKING, PACKING AND SHIPMENT

6.1 All bends shall be marked as per MSS-SP-75.

6.2 All loose and foreign material i.e. rust, grease, etc. shall be removed from
inside and outside of the bends.

6.3 All bends except bevelled ends shall be coated internally and externally with a
thin film of zinc chromate red oxide paint for protection against corrosion
during transit and storage. The coating shall be easily removable in the field.
Manufacturer shall furnish the details for the same.

6.4 Both ends of all bends shall be suitably protected to avoid any damage during
transit by means of metallic bevel protectors.

6.5 Package shall be marked legibly with suitable marking to indicate the
following:

a) Order Number
b) Package Number
c) Manufacturer’s Name
d) Size (Inches) and wall thickness (mm)

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 MECON LIMITED PROCESS & PIPING STANDARD SPECIFICATION
DELHI DESIGN SECTION

TITLE LONG RADIUS BENDS SPECIFICATION NO. PAGE 8 OF 8

MEC/TS/05/62/015 REVISION 1

7.0 WARRANTY

Purchaser will be reimbursed by Manufacturer for any bend furnished on this

order that fails under field hydrostatic test if such failure is caused by a defect
in the bend which is outside the acceptance limits of this specification. The
reimbursement cost shall include bend cost, labour cost and equipment rental
for searching, excavation, cutting out and installation of replaced bend in
position. The field hydrostatic test pressure will not exceed that value which
will cause a calculated hoop stress equivalent to 100% of specified minimum
yield strength of the attached pipe.

8.0 DOCUMENTATION

8.1 All documents shall be in English language.

8.2 At the time of bidding, bidder shall submit the following documents :

a) Reference list of previous supplies of bends of similar specifications.

b) Clause-wise list of deviation from this specification, if any.

c) Brief description of manufacturing and quality control facilities of the

Manufacturer’s works.

8.3 Within one week of placement of order the Manufacturer shall submit four
copies, of the manufacturing process and quality assurance plan for pipe and
bends.

Once the approval has been given by Purchaser any change in material and
method of manufacture and quality control shall be notified to Purchaser
whose approval in writing of all such changes shall be obtained before the
bends are manufactured.

8.4 Within four weeks from the approval date Manufacturer shall submit one
reproducible and six copies of the documents as stated in para 8.3 of this
specification.

8.5 Prior to shipment, the Manufacturer shall submit one reproducible and six
copies of test certificates as listed in para 5.3 of this specification.

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