SURF products

Bend restrictors

Bend restrictors prevent over-bending at the interface between flexible flowlines/umbilicals/cables and rigid structures by mechanically locking up.


They are normally used in static applications but, unlike bend stiffeners, only provide protection once the pipe has achieved the desired bend radius between the flexible line and rigid structures such as wellhead connections, J-tube exits, rigid pipe crossovers and PLET connections.

Designed in accordance with API 17L, BOE bend restrictors are manufactured in rigid structural polyurethane two piece units that are bolted together around the pipe.

Balmoral bend restrictor installation


Boltless bend restrictor

Balmoral has extended its bend restrictor range to include a genuinely boltless restrictor (patent pending).

This innovation allows fitting times to be slashed, offering huge savings in offshore installation costs. In line with Balmoral’s acknowledged track record for product improvement, value has been added by taking something away.

Some existing products claim to be boltless but, in reality, none of them actually are. Balmoral’s boltless restrictor retains industry leading performance while offering significantly reduced installation times and costs.

Balmoral boltless bend restrictor


  • Rapid installation time creating significant offshore savings
  • Revolutionary boltless interlocking method fully utilising the material’s strength
  • Superior load capacity for long and short term conditions
  • Excellent temperature resistance, specifically important to long term creep performance
  • Significant multiple unit cost efficiency savings
  • Minimises sub-supplier risk
  • Materials and design methodology API 17L 1&2 compliant


  • Interlocking male and female mouldings
  • Innovative interlock system (patent pending) removes the need for fasteners
  • Bend restrictor lockout prevents cable/pipe over bending
  • Proprietary design and testing delivers long service life in extreme environments
  • Material fully API 17L 1&2 certified
  • Material is mercury and MbAOC free (REACH compliant)

Design specification

Typical cable/pipe diameters: 20-450mm
Typical bending moments: 2-120kNm
Standard minimum bend radius: 1-8m
Materials: Balmoral marine polyurethane
Design life: 35 years (or specific project requirement)

These are indicative values as bespoke designs outwith these parameters can be achieved. Please contact Balmoral for more information.

Balmoral boltless bend restrictor

Balmoral boltless bend restrictor


Balmoral bend restrictor FEA analysis

Balmoral bend restrictor FEA analysis


Bend restrictor design analysis

BOE restrictors are designed using ‘Inventor/Ansys’, the recognised industry standard, using the following information:

  • Flexible pipe OD
  • Minimum bend radius
  • Service life
  • Length of coverage by angle or length
  • Support structure details
  • Flexible pipe min and max internal temperatures; operation and installation
  • Flexible pipe min and max thermal conductivity value if pipe is heated
  • Min and max installation air temperature
  • Min and max seawater operation temperature
  • Installation and operation shear force
  • Installation and operation bending moment
  • Flexible pipe stiffness if not taken into consideration in the bending moment and shear force loads

Balmoral bend restrictor range


End fittings

Balmoral offers a variety of options for bend restrictor end fittings (reaction collars) where a robust design is required to provide the smooth transfer of load from the project interface to the end of the restrictor string ensuring protection is maintained at all times.

Forged reaction flange
Using this method, Balmoral bend restrictors couple to the structure by means of a flanged (male) end fitting. Forged reaction flanges are manufactured using compliant material as a single body which is machine finished and requires no welding. They are supplied as split units and bolted together using B7M bolts.

Forged reaction flanges are coated with a standard marine grade paint system (NORSOK System 7B) and couple with the client’s end fitting. Balmoral does not supply the bolts to connect the reaction flange to the end fitting but this can be arranged if required.

PU reaction flange
PU reaction flanges are the connecting point between PU bend restrictors and the subsea termination interface; these are designed to match clients’ end fittings. The PU reaction flange design is based on the bend restrictor as both components share the neck and pin geometric sections and utilise the same material.

PU reaction collar
Using this method, bend restrictors couple to the structure by means of a PU fitting connected to a steel flange located within the groove of the end fitting. Steel flanges are supplied in two halves with a pitch circle diameter (PCD) to match the PU end fitting.

All the options above can be supplied in Balmoral’s standard welded assembly format.



Balmoral bend restrictor end fittings