Bend Restrictors
Are present at the interface between flexible service lines (flexible flow-lines, umbilicals or cables) and rigid structures to prevent the over-bending of the service line during installation and service.
They are designed to be flexible but lock at a bend radius (MBR) greater than that of the service line, providing protection to the line from buckling or over bending.
Near neutrally buoyant half vertebra (shore 82D) are joined with corrosion resistant fasteners (UNS S32760).
Using extensive experience DGDG-EU have designed standard parts that comply with API 17J.
3. Agenda
Slide
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Oct - MMXIII
Introduction
Agenda
Polyurethane bend restrictors
Vertebra material selection
Standard internal Ø
Service line MBR & Ø
Variables
Vertebra moment resistance (M )
2nd Moment of area (I )
Line tension (F )
Factors of safety
DGDG-EU
13. Vertebra moment resistance
14. Line tension
15. Other material selection
------------------------------------------16- 20. Examples
21. Bolt calculations
22. Standard products
23. Different vertebra & materials
24. Bespoke designs
25. AOB
26. Thank you
27. Contact
Bend Restrictor Standardisation
3
4. Polyurethane bend restrictors
• Are present at the interface between flexible service lines (flexible
flow-lines, umbilicals or cables) and rigid structures to prevent the
over-bending of the service line during installation and service.
• They are designed to be flexible but lock at a bend radius (MBR)
greater than that of the service line, providing protection to the line
from buckling or over bending.
• Near neutrally buoyant half vertebra (shore 82D) are joined with
corrosion resistant fasteners (UNS S32760).
• Using extensive experience DGDG-EU have designed standard parts
that comply with API 17J.
DGDG-EU
Bend Restrictor Standardisation
4
5. Vertebra material selection
•
•
•
•
•
Polyurethane - Generic
Specific gravity
Tensile strength (σ ) 41-64MPa
Operating temperature
Standard colour
• Sub supplied
DGDG-EU
= 82 Shore D
= 1.14
= 41MPa
= -10° + 60° C
= Yellow
3.1B Certified
Bend Restrictor Standardisation
5
7. Service line minimum bend radius
& service line Ø
Service line MBR (l ) = 10 x service line Ø
DGDG-EU
Bend Restrictor Standardisation
7
8. Vertebra moment resistance & line
tension calculation definitions
M
σ
I
D
d
F
l
DGDG-EU
=
=
=
=
=
=
=
Moment resistance
Tensile strength
2nd moment of area
External Ø
Internal Ø
Line tension
MLR restrictor (≥ MBR umbilical)
Bend Restrictor Standardisation
8
9. Moment resistance calculation (M )
hollow cylinder
• Bending theory - peak bending moment - cylinder
2𝜎𝐼
𝑀=
𝐷
(Ref:- Mechanics of Engineering Matl's -Benham & Crawford)
DGDG-EU
Bend Restrictor Standardisation
9
10. 2nd moment of area (I )
hollow cylinder
𝜋
𝐼=
× 𝐷4 − 𝑑4
64
DGDG-EU
Bend Restrictor Standardisation
10
11. Line tension (F ) at 90°
𝑀
𝐹=
𝑙
DGDG-EU
Bend Restrictor Standardisation
11
12. Safety factors
•
•
•
•
Line tension MBR
Fail - Material – supplier
Low
Max
DGDG-EU
Bend Restrictor Standardisation
20%
0-33%
25% of Fail
50% of Fail
12
13. Standard moment resistance
Moment resistance kNm
Type (Fail)
(low)
(Max)
T012
22
5
11
T015
45
10
20
T019
65
15
35
T025
137
35
70
T033
221
55
110
T044
437
110
220
T057
870
215
435
T070
1407
350
705
DGDG-EU
Bend Restrictor Standardisation
13
15. Other material selection
•
•
•
•
Fasteners
End termination
Anodes
Paint
UNS S32760
CS S355
Norsok std
Norsok std
• Sub supplied
DGDG-EU
3.1B Certified
Bend Restrictor Standardisation
15
16. Example T033
Vertebra internal Ø (d )
& minimum lock radius (r )
•
•
•
•
Element internal Ø (d )
MBR (l ) = 0.34m x 10
r
r
= 0.34m
= 3.4m
= MBR + 20%
= 4.1m
Note: r is the centre of the unloaded restrictor geometry.
DGDG-EU
Bend Restrictor Standardisation
16
17. Example T033
Moment resistance (M ) calculation
•
•
•
•
•
Service line Ø
Minimum clearance (c )
Internal Ø (d ) = 0.33 + c
Element wall (t )
External Ø (D ) = d + 2t
DGDG-EU
Bend Restrictor Standardisation
= 0.25-0.33m
= 0.01m
= 0.34m
= 0.05m
= 0.44m
17
18. Example T033
nd
2
moment of area (I )
𝜋
4
4
𝐼=
× 0.44 − 0.34
64
∴
DGDG-EU
𝐼 = 1.18 × 10ˉ³𝑚4
Bend Restrictor Standardisation
18
20. Example T033
line tension (F ) at 90°
221𝑘𝑁𝑚
𝐹=
3.4𝑚
∴ 𝐹 = 65 kN
DGDG-EU
Bend Restrictor Standardisation
20
21. Bolt calculations
Are not covered in this presentation, to
determine the bolt size extensive calculation
is required for each restrictor involving the
compressive strength of the polyurethane
and the tensile strength of the bolt material.
The sizes on the following chart are based
upon established historic values.
DGDG-EU
Bend Restrictor Standardisation
21
25. Bespoke design
• What are the possibilities to go outside the
standard manufacturing program?
• DGDG-EU has experience and knowledge to
design all types of bend restrictors, from
polyurethane to steel and hybrids.
DGDG-EU
Bend Restrictor Standardisation
25