Mach III recently supplied custom torque limiters for a salmon hatchery in Port Armstrong, Alaska. This hatchery uses moving fences — or “crowders” — to push adult salmon from one end of a 50-foot raceway to the other end, corralling the fish for egg and milt harvesting. The hatchery uses a direct drive motor system that must be manually operated. 

Once the fish density reaches its predetermined limit, the operator turns off the drive. As the salmon are removed from the crowder’s receiving end, the density lessens, and the operator turns the drive on again to push more fish forward. In an ideal situation, the operator would activate the crowder, which would continuously push the fish forward as other salmon are removed, thus maintaining a consistent density.

Although the company had friction torque limiters in place, these components required frequent disc replacement. What this company needed was a hands-off motion control solution that could begin slipping once the system reached its preset resistance point, all while inching the salmon forward with constant pressure.

To meet these application requirements, Mach III engineers designed a custom C5D2K-002 clutch to retrofit the hatchery’s crowder system, enabling the operators to monitor the operation without worrying about manually turning the drive on and off. The clutch incorporates a dual port rotary union for actuation and is sealed for protection against the wet environment. The drive disc is ventilated via an air inlet and filter vent, allowing cool air to flow through the case and dissipating the 213-watt thermal load from the disc’s continuous slipping.

Additional specifications of this custom clutch included 1,557 inch-pound (in-lb) capacity, operating pressure of 30–40 pounds per square inch (psi), and cooling air pressure at 5–10 psi.

In addition, because the initial rotations per minute specification was higher than needed, the hatchery installed a variable frequency drive (VFD) to reduce the drive motor speed, cutting down the friction temperature from 240° to 120° F. After installing the new clutch, the company has informed us that it has been functioning flawlessly, enabling the hatchery to successfully harvest 50 million eggs with zero problems. Thanks to the hatchery system’s higher efficiency and throughput, our client can now begin its egg-take procedures without worry.

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