NF Series Non-contact Backstop
NF series non‑contact sprag‑type holdback is dedicated anti‑reverse safety device for bucket elevators and belt conveyors. During normal running, internal sprags keep non‑contact status with nearly zero wear. Instant self‑locking occurs once equipment stops to prevent drum reverse rotation and material back‑flow.
Main Features
1. Scope and Application
NF series non-contact backstop is an anti-reverse device mounted on high-speed shafts. It features reliable backstop performance, easy disengagement, large anti-reverse torque, light weight and convenient installation. Its comprehensive mechanical performance is obviously superior to other backstop devices. It is widely applied to belt conveyors, bucket elevators, scraper conveyors and other equipment requiring anti-reverse function.The NF backstops manufactured by our factory fully comply with JB/T9015-2011 standard. Meanwhile, to facilitate customers’ installation, we also supply non-contact backstops with anti-rotation base, marked as model NFG.
2. Working PrincipleInside the backstop, multiple special-shaped sprags are arranged in the raceway formed by the inner and outer rings. When the inner ring rotates in the forward direction, it drives the sprags to rotate together. Within a certain speed range, the sprags deflect under centrifugal force and separate from the inner and outer rings, achieving wear-free operation. When the inner ring rotates reversely, the sprags come into contact with the inner and outer rings under the action of springs and wedge them into one unit, so as to bear the reverse torque transmitted by the inner ring. |
 |
3. MOdel and Marking
3.1 Meaning of Model Code
3.2 Marking Examples
NFS125-100 means: Non-contact backstop with inner ring rotating clockwise, rated anti-reverse torque of 12500 N·m and mounting bore diameter of 100 mm.
NFN80-90 means: Non-contact backstop with inner ring rotating counter-clockwise, rated anti-reverse torque of 8000 N·m and mounting bore diameter of 90 mm.
Structural Sketch of NF Series Non-contact Backstop
