The Ovivo® Stone TrapTM system removes small stones and rocks from screenings when water is used for screenings transport. If not removed, stones and rocks will result in premature wear of the screw mechanism used in screenings compaction and dewatering. Since water is used to transport screenings in many applications, such as with Ovivo's center flow and drum screens, the Stone Trap is an ideal pre-screening method.
  • Protection of screenings handling equipment
  • Low operating costs and minimal operator attention
  • Extends the life and reduces the maintenance of a plant’s screenings compaction equipment
  • The automatic system does not require manpower to empty hoppers or the like
  • Collected rocks and gravel are water free
  • Demonstrated return on investment

The Ovivo® Stone Trap™ system is a simple piece of equipment that can result in much longer life expectancy and significantly reduced maintenance on expensive screenings compaction equipment. Stones and rocks entering the compaction equipment not only reduce the life of the equipment but can also cause it to fail. The Stone Trap system is part of the recommended screen package for Ovivo’s Brackett Green® center flow and drum screens for sewage treatment.


The Stone Trap system is designed to collect all heavy grit and gravel particles greater than 8 mm in diameter and a specific gravity of greater than 2.65. The system’s hopper is flange mounted at the bottom of the screenings trough prior to the screenings compactor. The lighter screenings are carried over the Stone Trap hopper and the heavy stones and grit fall into the hopper for processing.

The Stone Trap hopper features an angled 6 inch diameter shaftless screw which is initiated by a timer. The screw rotates at 12 RPM, lifting the gravel and small stones to the discharge point, where they then fall into a collection bin in a relatively dry state.

What size stones are removed by the Stone Trap system?

The Stone Trap system collects stones and gravel which are larger than 8 mm.

What if I don’t use water to transport the screenings?

The Stone Trap system is only applicable for screenings which are transported by water to the compaction equipment.

Can the reduced wear to the compaction equipment be quantified?

This is site specific since some sites have more rocks and large gravel than others. However, rocks and large grit which enter the compactor is the most common cause of compactor failure.

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