Reasons for Non-Reverse Ratchets
When an operator says he "wound up the pump to full speed," he is being more than poetic… especially if he is talking about deep well turbine pumps. He is transmitting energy through the pump into a column of water. Part of this energy is stored in the water, much like the energy stored in a "wound up" spring. During the pumping operation, this energy remains stored in the water column; but it acts as a fast brake on the motor and pump on shutdown.
Shaft bearings serve the typical deep-well turbine pump at regular intervals; many of these are water lubricated. When the pump power is removed, water flows back into the well, driving the pump as a turbine until the water level drops to its static or equilibrium point. As it flows back into the well and the water level drops below the upper shaft bearings, they will operate dry. If allowed to run dry for any period of time, they, of course, will fail. Locking the motor with an effective backstop eliminates this source of failure in water-lubricated bearings.
Locking the motor also slows the flow of water back into the well during shutdown. Therefore, it sharply reduces the stirring of solids, sand, or other foreign particles caused by the unrestricted turbulence of backflow through freely rotating impellers. It also reduces the vacuum pulled on irrigation systems not protected by check valves, thereby preventing the collapse of thin-wall aluminum irrigation pipes.
The possibility of a single-phase reversal still provides another reason for backstops. Should a three-phase pump motor be subjected to a "single-phase" condition, water will flow back into the well, driving the pump and motor backwards. A backstop would lock the motor against a reversal allowing the protective devices to sense the single phase-locked motor and disconnect power before any damage happens to the motor or pump.
High-speed backspin is fairly common in industrial applications where turbine pumps are often used as boosters in pressurized systems. In multi-pump systems, the entire output of other pumps may try to circulate back through a pump that loses power. In single pump systems, the accumulated output from a lengthy pressurizing cycle may backflow. Fast action against reverse rotation is required. The BALLOMATIC backstop provides it, often much faster than the action of an output check valve.
Another offered feature is Impact Dampening on size 499 frame and larger. This feature reduces the shock when the ball engages the stationary ratchet. This is accomplished by using a large "C" spring, bonded brake lining on the stationary ratchet, and a spring-loaded dampener plate. On impact, the "C" spring dissipates the energy and reduces shock.
This feature allows U.S. MOTORS® brand vertical pump motors with non-reverse ratchet to operate at any depth setting. U.S. MOTORSis the only manufacturer to offer this feature and not put a depth limitation on the ratchet.