As the requirement for flexible risers and umbilicals progresses into ever deeper water, the performance of the clamping systems required to maintain the buoyancy, ballast or tethers in position has changed significantly.
On occasion, risers also have an insulating layer which in many cases will be subject to creep over the service life of the riser.
The range of variables encountered through the design life of the clamp includes variation in diameter due to changes in internal pressure, flexing of the riser/umbilical as well as temperature and tension fluctuation.
Whilst the clamps are fitted directly onto the outer layers of the riser/umbilical, they are normally required to transfer the clamping load through the outer layers to the internal armour layers. This load transfer is designed to prevent slippage between the layers - caused by in-service and deployment loads - with an acceptable safety factor.
Balmoral Offshore Engineering has designed a unique generation of clamps to ensure optimum performance for specific operating conditions.
Typical example of a three-piece clamp
High performance clamp
This one-piece product is designed for high clamping load situations to resist the axial movement of large buoyancy and ballast loadings. The high performance clamp is designed to control the contact pressure onto the flowline allowing the accommodation of large diameter expansion/contraction due to its low stiffness and excellent spring properties. The clamp is installed directly onto the flowline using a specialised tool allowing accurate loads to be generated while minimising installer fatigue.
The high performance clamp in summary:
- Suited for high loading/large buoyancy applications
- Riser outer diameter tolerance accommodated by hinge feature
- Riser diameter variations during operation accommodated by excellent spring properties of clamp assembly
Designed for intermediate load situations this one-piece clamp resists the axial movement of moderately large buoyancy and ballast loadings.
The intermediate clamp is engineered to control the contact pressure onto the flowline allowing it to accommodate large diameter contractions due to the low
stiffness and excellent spring properties of the material.
The clamp can be installed directly onto a flowline with torqueing bolts or through the use of an installation tool to induce a load into the clamping strap.
The intermediate clamp in summary:
- Best suited for intermediate loading applications where low clamping pressures are essential
- Riser diameter variations are readily accommodated due to the excellent spring stiffness of the clamp assembly
This three-piece device is designed to clamp directly onto flexible flowlines, risers and umbilicals to prevent a module assembly from sliding along the length of the flowline whilst allowing the module to rotate freely.
This clamp is best suited for umbilical or small diameter risers where low clamping pressures are required.
The standard clamp in summary:
- Best suited for low clamping pressure applications
- Riser outer diameter tolerance readily accommodated while retaining consistent clamping load to resist slippage
The integrally clamped module removes the need for a separate clamping system by attaching directly onto flexible flowlines, rigid pipelines, umbilicals and risers. Custom designed pads placed within the recess of the module accommodate riser diameter expansion and contraction while generating consistent clamping loads to resist slippage.
These pads also allow the module to accommodate upper and lower deviations of the nominal outer diameter of the flowline. The module can be installed using hydraulic cylinders, removing the need for bolting modules together and minimising installer fatigue.
The integral clamp in summary:
- Variation in riser outer diameter is readily accommodated while generating consistent clamping loads to resist slippage
- The clamping load can be generated by hydraulic tool, minimising installer fatigue
Next: Buckle mitigation buoyancy