​

Fundametal Technologies’ Detritor Mechanism is a robust, process-optimised solution for grit removal in sewage treatment plants (STPs). Installed during pre-treatment or primary treatment stages, our detritor system protects downstream equipment from abrasive wear, maintains hydraulic capacity, and ensures smoother biological and tertiary treatment operations. Every element is engineered for durability, torque resilience, and sustained performance in variable flow conditions.

1. Inlet Chamber & Flow Distribution Baffles

Incoming flow from a narrow approach channel is diverted into a broader silting basin using deflection baffles. These are fabricated from stainless steel or epoxy-coated carbon steel and are mounted with precision-designed brackets and supports. Their purpose is to uniformly spread the influent across the basin width, eliminating dead zones and preventing uneven silt deposition.

2. Silting Basin

This square-shaped recessed chamber is hydraulically designed to retain approximately 60 seconds of peak flow, allowing heavier grit particles to settle. Multiple raking arms fitted with metal baffles sweep the settled silt toward a peripheral transfer chute. At the terminal end of each arm, a sand box with a protective top cover ensures that captured grit is not re-suspended when arms pass the high-velocity inlet zone.

A weir and wall structure at the outlet side sets the liquid level for the entire detritor unit.

3. Raking Mechanism

The raking mechanism is built to handle extreme torque loads caused by grit accumulation. It comprises:

• A central hollow shaft with a top flange and lower brackets to mount 2 to 4 raking arms, depending on basin size.

• A threaded drive shaft coupled via shaft keys, allowing mechanical lifting of the rake mechanism through a top-mounted nut—useful during restart or overload conditions.

• Stay wires and supports allow fine-tuning of rake camber and level, ensuring consistent floor contact and efficient grit gathering.

4. Calibrated Drive Head with Real-Time Torque Monitoring

Our two-stage gearbox (worm-worm or worm-helical) drive head is equipped with electronic torque monitoring, a major upgrade over traditional spring-loaded drives.

• Primary Output Stage: Monitored for torque in real time.

• Overload Controls:

  • 100% = Design load

  • 135% = Alarm

  • 150% = Automated shutoff

Due to the high gear ratio (2000–5000:1), traditional motor overload trips are too slow to respond—potentially damaging the gearset. Our design preempts this failure mode and ensures longer service life.

5. Transfer Chute

The grit swept by the rake arms is discharged into an inclined transfer chute that hydraulically links the silting basin with the classifier chamber. With no moving parts, this chute is sized to ensure self-cleansing velocity and eliminate grit choke-ups. Its performance directly affects the entire system's throughput and is thus tuned to the detritor’s rated flow.

6. Classifier Chamber

This right-angled triangular chamber is designed to lift and dewater separated grit. The standard solution provided is a shroudless screw classifier, but rake classifiers are available for retrofit-only applications.

• Screw Classifier (Standard):
  Features an industry-first shroudless auger that eliminates trapped water pockets found in conventional designs. The auger lifts grit continuously along a sloped chamber floor (35°–45°), ensuring dry discharge with minimal grit return.

• Rake Classifier (Legacy – Optional):
  Discontinued as a standard offering, now only supplied for replacement of older units. These function with an intermittent motion and require a shallower floor angle (15°–25°) to control backflow during the reset stroke.

7. Organic Return Pump

A low-head axial propeller pump is installed in the classifier chamber to return liquid to the receiving chamber upstream of the silting basin. Designed for 0.5 m static head, this custom pump includes:

• A high-volume axial impeller,

• Receiver pipe,

• Support bearing,

• And a direct-drive motor.

It maintains hydraulic continuity, drawing fresh water through the transfer chute as it evacuates clarified water from the classifier, thereby sustaining grit transport velocity.

8. Screw Classifier Drive & Overload Protection

Our screw classifier drive system includes:

• Dual-End Support:

  • Bottom: Polymer-lined submerged bearing.

  • Top: Thrust isolation bearing unit.

• Double-Axis Shear Pin Coupling:
  Between the auger shaft and top bearing shaft—acts as a mechanical fuse.

• Torque Transmission:
  Via a roller chain and sprocket system, calibrated for speed and load.

A geared motor drives the top sprocket, providing steady, protected torque to the auger.

This setup ensures continuous, reliable operation and protects key components from jamming-induced failures.

Why Choose Fundametal Detritors?

• Torque-Resilient Design: Calibrated drives and mechanical lifts for overload handling.

• Zero Choke Transfer Path: Optimised chute for continuous grit flow.

• First-in-Industry Shroudless Classifier: Reduces water retention and biological fouling.

• Retrofit-Ready: Rake classifier support for legacy systems.

• End-to-End Mechanical Integration: From baffles to classifiers, all components engineered in-house.