Drive shafts & couplings
The drive shaft connects motor to gear reducer across a span that is never quite aligned and never stays aligned. It is a cheap component whose failure is not cheap at all.
Understanding the component
A cooling tower driveline consists of a spacer tube with a flexible element at each end. The flexible elements (normally flexible disc packs or composite flex discs) transmit torque while accommodating the angular, parallel and axial misalignment that exists between a motor on one support and a gearbox on another. Both supports move: thermal growth, structural settlement and the ordinary flexing of a wet timber or steel deck all contribute.
Composite drive shafts changed this component substantially. Carbon fiber and epoxy spacer tubes tolerate more misalignment (around one degree per end) while spanning roughly twice the distance of a metal coupling. That matters because it eliminates the intermediate steady bearing that older multi-section drivelines needed, and an intermediate bearing inside a cooling tower plenum is a component that requires periodic lubrication in a place nobody wants to go.
Composite shafts are also light, which reduces vibration and bearing loads on the motor and gearbox at both ends, and they do not suffer the fretting corrosion that eventually affects metal disc packs in a saturated atmosphere.
Dimensional survey of a drive shaft ahead of a mechanical replacement.
We supply components for cooling towers from every manufacturer, including towers whose original makers no longer exist. If it is on your tower, we can identify it.
What actually goes wrong
These are the failures we find in the field, roughly in order of how often we find them. If you recognize one, we can usually tell you what to check next over the phone.
| Failure | What it means |
|---|---|
| Disc pack cracking | Fatigue cracks in the thin metal laminations of a flex disc. This is the classic driveline failure and it is visible on inspection well before it lets go. |
| Fretting corrosion | Metal disc packs working against their mating faces in wet air. Produces red-brown dust around the coupling bolts. |
| Loose or corroded coupling bolts | Bolt torque loss is progressive and mundane and accounts for a large share of failures. |
| Misalignment | Usually the root cause rather than the symptom. A driveline forced to work beyond its misalignment capacity destroys its own flex elements, then the bearings either side. |
| Shaft "fuzzing" | On older uncoated composite shafts, UV degradation breaks down the surface resin and exposes fibers. Current shafts carry a UV-resistant coating. |
Manufacturers and product lines
We are independent, so the recommendation follows your tower, your water and your duty rather than a single manufacturer's catalog.
Addax
Composite couplings built to aerospace-derived standards, with patented unitized carbon fiber/epoxy flexible elements. High misalignment tolerance, no fretting corrosion, extended single spans without intermediate bearings.
Amarillo
Composite drive shafts with high-strength composite flanges, carbon fiber/epoxy spacer tubes, 316 stainless flange hubs and hardware (monel optional) and a UV-resistant coating. Dynamically balanced to AGMA 9000-C90 Class 9 and tested to peak overload torque before shipment.
Rexnord Thomas
Flexible disc couplings designed in accordance with CTI standards, in zinc-plated or all-stainless construction with stainless disc packs.
TB Wood's
Formflex flexible disc couplings for fan drive applications, including four-bolt metal disc designs and TrueTube composite torque tubes. Composite floating-shaft couplings are the recommended replacement for older multi-section drivelines and can span considerable distances without a center support bearing.
Names you may find on the nameplate
Including lines that are no longer current. Many of the towers we work on are thirty to fifty years old, and identifying the modern equivalent of a discontinued component is part of the job rather than an obstacle to it.
- Addax
- Amarillo
- Rexnord Thomas
- T.B. Woods Formflex
- Marley
What we would tell you on the phone
Retiring an intermediate bearing is usually worth it.
If your tower has a multi-section driveline with a steady bearing in the plenum, a single-span composite shaft removes a lubrication point, a failure mode and a confined-space entry from your maintenance schedule.
Measure the installed span accurately.
Shaft length is set by the actual distance between motor and gearbox flange faces on your tower, which frequently differs from the drawing. We measure it on site where we can.
Replace the guard too.
Driveline guarding is an OSHA item and it is often the part that was never refitted properly after the last repair.
Usually replaced or inspected at the same time
Gear reducers
Right-angle fan drives, including direct replacements for the Marley Geareducer line. Frequently rebuilt in place.
View componentMotors
Cooling tower duty fan motors: severe duty and premium efficiency, single and two-speed, any horsepower.
View componentFans
Fiberglass and aluminum fan assemblies, blades and hubs: Hudson, Amarillo Chittom, Moore and Cofimco.
View componentVibration switches
Mechanical and electronic vibration cut-outs: Murphy VS2, PMC/BETA and Metrix. The cheapest protection a fan drive can have.
View componentSend us the nameplate and we will identify it
The fastest route to a correct quote is a photograph of the nameplate and of the component in place. Model numbers get superseded and drawings go missing; photographs do not lie.
- Phone
- (713) 643-0691
- Shop & office
-
3811 Cedar Blvd Ste A
Baytown, TX 77523