The International Energy Agency has stated that the World must invest $26 trillion (£16.7 trillion) over the next two-decades to avert a global energy shock. Despite recent events, industry commentators still believe much of this investment will be directed at nuclear power. Many new stations will be built and the infrastructure of these, and existing nuclear installations will come under pressure to perform reliably, as never before. This, in turn, will mean unprecedented levels of support from companies that supply specialist products and services to the industry.
Altra Industrial Motion has anticipated this development and has produced, via its Group companies, a package of electromechanical power transmission products designed for use in critical, safety-related nuclear power applications, where reliability and accuracy are necessary to avoid costly downtime, assure safe operations and optimise production output.
At the core of Altra’s Group offering are high speed gear increaser and reducer drives from Nuttall Gear (formerly Westinghouse Gearing Division). The Nuttall SU high speed gear design offers the key advantage to nuclear operators of proven operation over millions of hours in approximately 50% of the nuclear power plants built by Westinghouse. The SU gear drives in these existing facilities continue to be supported through new units, replacement gearing and parts, and Nuttall Gear also offers a full rebuild service to original OEM specifications.
In new applications, Nuttall gear excels in designing, to AGMA standards, high speed drives for custom applications such as compressors, fans, pumps, and turbines. These drives offer proven reliability with features such as rigid cast iron or welded steel housings, dynamically balanced precision double helical gearing for uniform load distribution and quiet running, oversized split sleeve bearings for smooth, efficient running, split labyrinth non- contact oil seals for longer life, and self-contained forced oil lubricated gears and bearings.
Crucially for use in nuclear facilities, the Nuttall gear units are supported by options such as monitoring systems to measure temperature, pressure, and vibration, remote mounted lubrication consoles, and multi-speed shifters.
Also extensively proven in nuclear power applications, employing designs that deliver infinite life in critical applications, are Altra’s Bibby and Ameridrives ranges of high performance disc and diaphragm couplings. Designed and manufactured in compliance with API-671, and rated for operation up to 677,400Nm, these non-lube maintenance-free couplings have set new standards for life and reliability in the power generation market; particularly in critical applications such as boiler feed pumps, generator sets and gas compression.
Bibby’s latest HS series of disc couplings are manufactured from alloy steel, which is fully traceable. They have a unique design, which effectively drives in friction, rather than shear, to the disc assembly joint. This eliminates the potential for fretting during normal operation, and prolongs the life of the coupling.
The HS series also offers the benefit of a plug-in design which allows easy installation. This enables the couplings to be installed, and the flexible elements (disc packs) changed, without disturbing adjacent machinery. In addition, by nature of their design, disc couplings are torsionally stiff and backlash free; and they will also accept significant levels of angular, radial and axial misalignment without any loss of operating performance.
The Ameriflex range of diaphragm couplings offers features such as: 15-5 PH shot-peened stainless steel diaphragms, for improved fatigue strength and stress corrosion resistance; multiple separated diaphragms to provide power transmission redundancy and design flexibility; and field replaceable flex elements.
The ‘fitness for purpose’ of the Ameridrives diaphragm couplings for nuclear applications is ably illustrated by the use of 80-inch (203cm) coupling – the largest multiple diaphragm coupling ever built – to provide power transmission in the propulsion system of a nuclear submarine. The coupling is designed to deliver infinite life.
The third key element in Altra’s nuclear power package is Centrifugally Disengaged Vertical Backstop Anti-Rotation Device (ARD) from Formsprag – Stieber. This Altra Group company was instrumental in the development of long-life Anti-Rotation Device (ARD) for the reactor coolant pumps of pressure water reactors’ and continues to support the installed base of these devices by offering field inspections, factory rebuilding and new ARDs with improved bearing performance.
In addition to coolant pumps, Formsprag - Stieber ARDs are also used in other nuclear applications: as backstops for various pumping systems, cooling tower fan backstops, and overrunning clutches in rotating gear drives. Their widespread use in these critical applications is the result of their unique design, with virtually unlimited speed capability and torque holding facility (56,450Nm).
The ARDs feature lift-off sprags for no-contact running, no heat generation and long-life – exceeding 1O-year maintenance-free operation between recommended inspections. They have balanced torque arms to prevent reverse rotation, and use dynamically balanced hydrodynamic babbitted bearings and races for minimal wear and heat generation. Importantly for nuclear use, the ARDs also offer the facility to ensure performance compliance, with pressurised oil flow, and monitoring systems to measure temperature, pressure, and vibration. They are all 100% factory tested before despatch in an ISO 9001:2000 and AS9100 rated facility.