SPX BS to Provide Equipment for PELAMIS

PELAMIS, the giant sea serpent of Greek mythology, has been transformed in Scotland into an ocean wave power house (which generates electricity via the movement of waves) made by PELAMIS Wave Power Ltd.

Semi-submerged and positioned in the direction of wave propagation, this 120m-long metal serpent, weighing 750 tonnes, is made up of a train of five floating cylinders (each one 24m in length and 3.5m in diameter) linked together by universal joints.

It operates in water deeper than 50m, from 2km to 10km offshore.

Wave movement acts on a hydraulic cylinder located within each universal joint between the cylinders. The hydraulic cylinders propel a high pressure fluid to a turbine to produce electricity, which is then transmitted through a wire to the main underwater cable connected to the grid. PELAMIS‟s energy efficiency is virtually constant: its return is between 70% and 80%.

“The power generated by a single „snake pit‟ (30MW) could supply around 20,000 homes. Twenty locations with this capacity would be enough to cover the electricity needs of the city of Edinburgh with its population of 450,000 people; this is a real opportunity for renewable energy in Scotland.”

“Bolting”: the challenge taken up by SPX Bolting Systems

Given the large loads imposed by waves and the harsh environment to which the wave power house is subject, the bolting together of the elements is crucial. The elements in question are the 5 floating energy producing cylinders, the head cylinder and other internal fittings, such as the control panel. A few sections were pre-installed at the PELAMIS factory, near the naval dockyard at Leith in Edinburgh; the final work was carried out in the dock before launching. For optimal productivity and efficiency, PELAMIS Wave Power Ltd. chose hydraulic bolting tools by SPX Bolting Systems (SPX BS), a global manufacturer of hydraulic solutions for industry.

The work specifications turned out to be a serious challenge for SPX BS. The solution it came up with had to be capable of bolting pre-assembled structures to the cylinders both very securely and within a very short timeframe, taking account of the fact that space is often limited and that the parts would be subject to a very harsh environment: seawater.

This assembly process required a blend of clamping and tensioning techniques for numerous bolting applications: assembling hydraulic cylinders in position, fitting the pre-assembled hydraulic parts, and connecting the pre-assembled control system to the yellow head module.

SPX BS brought its highest performing solutions into play, including:

* TWSD3 hydraulic torque wrenches,

* Hydraulic spring tensioners from the new SRT range,

* ENS nut-splitters, unique on the market,

* PE55TWP-E110 and HPUTP150001 hydraulic pumps.

These products, which have been proved in the most demanding industries (nuclear, wind energy, oil and gas, mining etc.) offer high corrosion resistance and are fully adapted to the difficult environment represented by salt water, thanks to a nickel plating treatment.

The assembly of the modules was carried out extremely quickly thanks to SPX BS products, averaging 2 to 3 hours per section (as opposed to 4 to 5 hours for competitive models). Apart from the productivity benefits, this also meant that it was possible to reduce the operating time of the crane used to lift and hold the modules during their assembly, thus resulting in a reduction in costs. The SPX BS team had previously all undergone bolting training approved by API and ECITB.

The lead engineer for the project was highly impressed with the superior quality of SPX BS‟s bolting tools. Their user-friendliness makes the installers‟ work easier and reduces their fatigue, whilst offering them a significant gain in time.

 Highly innovative products

TWSD3 torque wrenches boost productivity by 40%

TWSD3 is part of the new generation of SPX BS torque wrenches.

It is more efficient and faster and is a third smaller in size compared to aluminium alloy wrenches. What is more, the 360° torque arm, together with the hydraulic manifolds high-speed rotating multi-axis connector bring a maximum level of flexibility and a very quick operational cycle, with a minimum of 30 degrees of rotation per stroke, all of which give an increase in productivity of 40%. These features mean it can be used in confined spaces with greater ease and less fatigue (it only weighs 4.5 kg); something which is greatly appreciated by the PELAMIS technicians, who also sometimes work in tight spaces.

Tool changes can also be performed ultra-fast thanks to a simple push-button engagement of the square drive and reaction arm, which enables rapid change between tightening & un-tightening. The technician‟s safety is guaranteed because the elements mechanism is fully placed within the tool housing, thereby minimising the risk of finger trapping and injury.

With their higher stiffness and torsional strength, the TWSD3 square torque wrenches have a torque constant of 4,160 Nm and offer unparalleled reliability. In addition, SPX BS gives them a lifetime warranty against potential manufacturing and equipment defects.

These wrenches also offer a very high degree of reliability. In order to prolong tool life, a fine toothed drive-pawl guarantees full engagement in the ratchets teeth, and a floating piston design eliminates stroke misalignment, while the simplicity of the design reduces the number of parts by 25% compared with some competitive wrenches.

Various qualities of these tools meant PELAMIS‟s chief project engineer was completely sold: the robustness of their build, the hydraulic manifolds flexibility of 170 x 360 degree angle of rotation, their user-friendly operation, the floating hydraulic piston (which reduces considerably wear on the internal components), the built-in safety valve and the fine-toothed ratchet wheel. These technical qualities noticeably defer maintenance costs and reduce production hold-ups.

 SRT, hydraulic spring tensioners unique in the marketplace

For PELAMIS, subject to the whims of sea-swell, it is vital to be able to predict with accuracy the load placed on the bolts during tightening. If the load strain is unequal, some bolts may loosen, while others could be subject to too great a load; such imbalance will weaken the structure, damage the bolts or result in leaks if the watertight joint is crushed or unloaded.

Thanks to the piston-stroke indicator, the PELAMIS technicians can gauge the clamping accurately, while an over-stroke valve prevents the piston from being accidentally over-extended which would lead to pressurised oil expulsion and seal damage. Besides operational savings which result, this feature also protects the operator from any oil discharge hazards.

The SRT hydraulic tensioners‟ automatic piston return, unrivalled on the market, yields a significant amount of saved time through reduced installation and re-set time (around 40% higher productivity) as the oil is constantly returning to tank when the valve is open. Besides the time saving, this function offers operators improved performance, reduced fatigue and increased safety and productivity.

Further still, the SRT hydraulic tensioners have an integrated misalignment compensator which allows bolt axis deviation of up to 5 degrees. This maintains the applied load, keeps all the components in place and reduces maintenance operations and consequently also costs.

The PELAMIS team used different models in the range offering sizes from ¾ to 3½ inches (M20-M100), operating with a maximum piston travel of 10mm and a maximum pressure of 1,500 bars. Operators particularly appreciated the automatic piston return (synonymous with a significant time saving), the end of stroke indicator function (which protects both machinery and operators) and the misalignment compensation.

 ENS, the very high performance triple blade hydraulic nut-splitter

Seized, corroded or deformed, nuts are often impossible to undo, and the only solution for releasing tension and removing the nut is to use a nut splitter. The ENS range of nut splitters by SPX BS are specially designed for BS1560 / ANSI B16.5 flanges, and enables fast and easy removal of jammed nuts from 3/4 to 3½ inches (M20-M100) in diameter. Equipped with a forged head which gives unparalleled strength and with its triangular triple-edged bladed design, ENS saves the operator time and effort so that when necessary, he/she only has to turn the blade through 120° to obtain a new cutting surface. It also means that you are always guaranteed to have a maximum performance tool. The ENS hydraulic nut-splitter is also fitted with a bolt-size graduation scale which allows pre-setting of the tools stroke and therefore avoids any damage to the bolt thread, enabling re-use. ENS is also available in an underwater version (hydraulic piston return).

 The hydraulic pumps

SPX BS also provided hydraulic pumps which operated the various tools. These supply hydraulic power via 2 pressure systems which can be regulated according to the needs of each operation – up to 700 bar for torque/splitting tools and up to 1,500 bar for tensioning tools.

The hydraulic tools supplied by SPX BS play an important role in PELAMIS‟s reliability and corrosion resistance to the marine environment, additionally providing training, technical support and expertise in solutions for the renewable energy sector.

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Offshore Nieuws Staff , November 30, 2011; Image: pelamiswave