Edited by Mary C. Gannon, Senior Editor
Stopping a heavy industrial operation quickly and safely during maintenance operations is easily accomplished with air clutches and brakes.
As machines get bigger, faster and smarter, maintenance remains a key challenge to many heavy equipment operators—the expense and lost time it takes to repair a down machine can be disastrous to an operation. Across nearly every industry that uses heavy equipment, machine end users are facing price pressures and looking to solutions providers to help increase efficiency and reduce the cost of ownership.
Stopping equipment cold
Air brakes deliver the quick actuation and stopping times that are a necessity in emergency situations or to stop large industrial machines for routine maintenance. They are actuated with compressed air rather than hydraulic fluid or oil.
Air brakes are basically spinning rotors or discs attached to a shaft. They feature a keyway attached to a gear, said Mike Williams, product line manager for Eaton’s Airflex brakes and clutches. As these gear teeth mesh with the metal discs, they actuate pneumatic pistons, which in turn push friction pads onto the metal rotors. For example, in a drawworks application, when trying to control and stop a drill bit, this rotating shaft provides just the right amount of air needed to the power head and pistons actuating and pushing the friction pads against the disc.
Air clutches help transfer power or torque between the engine and transmission, rather than supplying stopping power. They rely on compressed air for engagement and disengagement.
Clutches feature a “giant doughnut with a shaft or drum attached to it,” Williams said. This drum is bolted to one side of the rotating system. An output shaft from a motor is on the other side. In this situation, clutches connect and disconnect the two rotating shafts to transmit power and motion. When the clutch is engaged, it is used to slow the shaft. Eaton’s constricting brakes can also be used as clutches, too. When a constricting brake is applied in a clutching application, it will provide the higher torque needed to produce the friction on the drum.
Sizing an air brake is based on the required horsepower, stopping time and total energy. In addition, upper torque limits help with the horsepower and energy. “We can then determine what your maximum load is at that size,” Williams said. “A lot of times, the application sizes itself. When users give you those numbers, they know their system or environment can only handle a certain load. But we know what we’re limited to based on the torque, energy and horsepower.”
Safe, consistent options
Although electrical and hydraulic braking options are available, air-actuated brakes and clutches offer a number of advantages to industrial users. For example, said Williams, they offer faster response rates and are safer than hydraulic designs. Because they do not use oil, they avoid the risks of oil spills or leaks that may be present in their hydraulic counterparts. “If you leak air, it is not as detrimental as if you leak hydraulic fluid,” he said. “Fluid could penetrate the friction surface and then you’ll have trouble stopping a load because you’ll have oil on the friction surface.”
In addition, leaked or spilled oil can cause an incident that can take hours or days of downtime to clean up, create a hazardous working environment and put end users at risk of expensive environmental fines.
And while electrical options such as variable frequency drives and other ac drive motors exist, if there is a power failure, you will still need an option to stop motion. This makes these systems more complex, as many electrically controlled systems still need a fail-safe brake—like a caliper—to slow or stop motion in case of power outage.
Trends: bigger, faster, easy to maintain
Installed on machines operating in critical environments—from draglines, grinding mills and shovels in mining to drawworks for drilling rigs and tug boats and winches in the marine market—air brakes provide maintenance-friendly, easy-to-use stopping power that keeps industrial operations up and running. No small feat, considering the latest industrial trend of increasing machine size and speed means that brakes must perform in tougher-than-ever environments. As equipment gets larger, engines work harder to move machines faster, creating more heat. And as machines get hotter, brakes need to adapt to manage increased thermal loads.
Eaton is a pioneer in the air brake industry and its latest innovation is an example of how the industry strives to downsize designs while increasing thermal capacity. The Water-Cooled Third Generation Brake is a disc-type, externally water-cooled dynamic brake designed to dissipate extremely high thermal loads. By increasing coolant flow and redesigning the water jacket for quicker and more effective cooling, the brake can reach 1,000 hp per plate and allows for 60% lower pressure drop.
End users need brakes that provide reliable, cost-effective solutions that help keep operations running smoothly. Featuring the highest horsepower in its class, designs like these offer faster tripping time and give users the ability to downsize the brake in the same application—saving customers up to $60,000 per brake installation. The self-supporting brake also eliminates the need for costly outboard supports.
“This is an improvement upon existing technology to drill faster and drill harder with some improvements to increase the horsepower, eliminate copper cracking, and also to make some good operations and maintenance improvements to make downtime decrease,” said Williams. “In addition to that, we’ve added the support beams to eliminate outboard support on certain applications. And in certain applications, you can even downsize from a larger brake to a smaller brake. We’re trying to get the most thermal capacity in as small a package we can.”
These water-cooled designs can also help manufacturers reduce required maintenance by decreasing leakage caused by copper cracking, allowing up to 54% faster drilling while tripping into the hole and making easier wear adjustments that require no machining for repairing friction or wear plates.
Another unique disc brake technology comes in Eaton’s 138 floating house brake (FHB), which uses a floating housing instead of a floating rotor. The heavy-duty, air-cooled, spring-applied/pressure released disc brakes are rated for more than 430,000 lb-in. of torque, and built with a full 360° annular disc to extend friction pad wear life.
A key feature of the FHB brake is the Tapered Shaft Lock (TSL), which eliminates wear issues associated with spline and gear designs, while allowing for faster installation and maintenance. It also eliminates the need to heat the drum to install or remove it with a hydraulic press. The brake also includes long wearing organic friction pads arranged in a unique “pizza slice” design, providing workers quick access to each pad. By removing the need to completely tear down to replace one pad, downtime needed for repair is reduced from three hours or more to just one hour. With the FHB brake, operators maximize uptime—instead of taking a day or more to install or maintain, it takes just hours, saving time and money.
The future is smarter
Air brake and clutch designs must continue to meet the needs of increasingly complex, high-tech machinery. Eaton is building smarter brakes that include sensing and monitoring technology to make the equipment more responsive and able to give feedback or warn users of problems. Solutions on the market today include brake products with embedded temperature sensors or slip detection.