When asked to describe the most important features of Rexnord® Addax® composite couplings, Steve Hittmann, National Product Manager – Mechanical Drives at CBC, has a long list to go through: Corrosion resistance, high-misalignment capacity, excellent fatigue resistance, low weight, ease of installation and ease of maintenance, to name a few.
As the pioneer for advanced composite couplings, Rexnord first introduced Addax couplings for the cooling tower industry in 1987. More than 30 years later, the couplings are still market leading for the many benefits they bring to the efficient operation of cooling towers and other heating, ventilation and air conditioning (HVAC) systems.
CBC, in partnership with Rexnord, offers assistance with selection, design and installation of Addax composite couplings. Steve says this close partnership between the two companies is particularly beneficial to the end users because “no two coupling installations are the same.”
“Every coupling installation has unique coupling dimensions, therefore all Rexnord Addax coupling assemblies are made-to-order as per customer-supplied specifications. Rexnord provides exceptional lead time in delivering made-to-order products, which is generally two weeks, ex-factory, after the receipt of order. Locally stocked critical hardware and flex elements add to the products support infrastructure.
According to Steve, Rexnord Addax couplings are uniquely designed and manufactured to help reduce maintenance costs, eliminate redundant inventories and prevent equipment downtime. These features are incorporated in every component of the coupling, including the centre section (spacer), the elements, the flange and the stainless steel hubs and hardware.
“The full-floating centre section of Addax couplings weighs less than 25% of a comparable steel spacer. This enables easier installation because there is no need for a crane to install most Rexnord Addax advanced composite coupling systems,” says Steve.
“The specific modulus of the composite material is 3.5 to 5 times that of steel alloys, which means the composite spacers can span almost twice the distance of a comparable metal spacer without the need for intermediate bearings. To put into context, a single-length, 600-millimetre-long composite drive shaft from a Rexnord Addax coupling may weigh 45 kilograms while the steel counterpart would weigh about 230 kilograms and be in two sections,” he adds.
In what shows the versatility of Rexnord Addax couplings, Steve says the spacers can be formulated to offer specific levels of corrosion resistance, including the addition of a carbon black additive to provide additional ultraviolet light protection.
“Rexnord Addax couplings also feature patented integral flanges which are fabricated from continuous fibre material and bonded to the centre section with aerospace adhesives. This unique design has been tested over the years to provide excellent fatigue strength for cooling tower and HVAC applications,” says Steve.
Further, Steve says the flexible elements in Addax couplings are designed to facilitate long service life, high misalignment capacity and simplified installation.
“Fretting and stress crack corrosion are the leading contributors to metal disc pack failure. Rexnord’s patented composite element is designed as a unitised disc constructed of advanced composite material and 316 stainless steel bushings. As a result, it offers very high fatigue life while simplifying installation by eliminating the multitude of parts required for assembly.
“Rexnord Addax elements are offered in a number of sizes with different torque ratings. Each torque rating is based on static and dynamic tests to provide an infinite fatigue life at rated torque and misalignment.”
The recent introduction of the FALK CTA series Gear Drive now provides the customer with a complete packaged solution, available in 11 standard ratios ranging from 9:1 to 16:1, factory leak tested, excessive vibration, and noise tested prior to shipment with a QR code functionality to simplify asset management.
Apart from providing a full range of services around coupling selection, design and installation, Steve says CBC also works closely with Rexnord to offer special design options when requested by clients. “From adding brake discs and backstops to lock the cooling tower fans to providing spark resistant couplings for hazardous applications, we can study each application specifically and offer customised options in collaboration with Rexnord. This versatility is the beauty of the Rexnord Addax coupling and/or CTA Gear Drive package. It is a truly customer-focussed solution.”
Rexnord Addax Composite Coupling
• Cooling towers
• Vertical pumps
• ISO 14691
• ATEX II 2G c T5
Special design options:
• Brake disc
• Spark resistant