In municipal and industrial wastewater projects across Thailand, vertical pumps and lift stations are widely used. Due to elevation differences and high static head, a power failure or valve misoperation can generate significant reverse flow in the pipeline. This reverse water column applies a back-driving torque on the pump shaft and motor, causing coupling and bearings to suffer sudden shock loads. Over time, this can lead to noise, cracks, and even shaft failures. Traditional electromagnetic brakes and external brake units help to some extent, but they are complex, generate extra heat and incur considerable maintenance costs.

For compact vertical pumps with relatively small shaft diameters, we prefer to embed a thin-section needle-roller one-way clutch inside the coupling or intermediate shaft, creating a “hidden backstop” in the drivetrain. Our company supplies the Suma DC series specifically for this kind of application. Models such as DC30, DC32 and DC3175A are suitable for approx. 30–32 mm shafts and feature a needle-roller cage design with very compact outer diameter and width, making them ideal for press-fitting into coupling bores or gear hubs.

During normal operation, the rollers in the DC clutch are disengaged, so friction between inner and outer race is minimal and does not significantly increase system heat. When the pump stops and reverse flow or back-driving torque occurs, the rollers wedge between shaft and housing, providing instant reverse locking and preventing the impeller and shaft train from being driven backward. Compared with external brakes, this solution does not require additional brake discs or brake units and does not consume extra axial space.

Thai pump-set suppliers who adopted Suma DC30/32/3175A in new designs have observed much more stable shaft behavior during shutdown tests. Reverse flow impacts are contained within the pump and pipeline, rather than being transmitted through the coupling to the motor. Because the backstop function is integrated inside the coupling, the equipment retains its usual appearance, operators do not need extra steps, and maintenance personnel only inspect the coupling assembly during major overhauls. For municipal owners focused on stable operation and easy maintenance, this “invisible but effective” one-way protection is becoming an increasingly attractive option.