Ovivo Screw Classifiers

The J+A screw classifier systems are free-standing units used for the separation of mineral grit from other types of solids. The screw classifier hopper maintains a water level through a series of weirs. A peripheral weir removes floating solids and a second weir positioned within the trough wall removes other solids that are lighter than grit. A hydrocyclone can be used to receive the flow and reduce the liquid delivered to the classifier, retaining the mineral particles.
  • Dewatering of grit from grit collection systems
  • Separation of grit from water
  • The J&A Grit Classifier works in conjunction with a cyclone to reduce the volume of pumped water to the classifier

Classification is an operation in which solid grains of mixed sizes and often different specific gravities are allowed to settle through a fluid under such conditions that separation will be made between slower and faster settling particles. The main purpose of the classifier is to carry out such separation, so as to effect a definite change in the size composition of the granular material. At the same time, the classifier accomplishes the equally important function of dewatering the grit and elevating it for discharge. In every classifier operation, there will be a feed, a rotating screw, an underflow and an overflow.

  • Requires minimal maintenance due to an automatically lubricated bottom bearing
  • Provides clean grit for further processing
  • Two (2) classifier sizes are available – with or without a cyclone

The J+A classifier body is typically provided in either 304 or 316 stainless steel, which has a much longer life than painted carbon steel. The screw is constructed of ASTM A36 carbon steel instead of stainless steel so it can withstand the normal wear and abrasion inherent in grit separation processes. The bottom bearing, with automatic lubricator, can be replaced without removing the classifier screw, reducing labor costs when bearing replacement is required.

An Krebs cyclone, which is capable of processing pumped grit/water mixtures of up to 500 GPM and is also used for the degritting of sludge, can be fitted onto the classifier to further enhance it’s capabilities. In lieu of a cyclone, an air-lift type of grit pump may be used to encourage gravity flows.

The dewatered grit product will typically pass the paint filter test, which may be required for ultimate disposal of the collected grit product.

The grit / water mixture enters the settlement bowl of the screw classifier unit where the water level is maintained by a series of weirs. A peripheral weir removes any floating solids and a second weir is positioned within the trough wall to scalp off those other solids that are lighter than grit.

As the grit settles within the main trough an inclined archimedean screw elevates and transports the grit above the water level. The grit product is dewatered as it is raised by the screw to a high discharge point. All extraneous solids and water are drained to the main sewage flow.

Design Criteria
Maximum capacity – up to 23 l/s
Grit size – commonly 0.2mm, 2.65 s.g.
Motor power – drive unit 0.75 kw or 1.1 kw.
Drive protection – IP55 (explosion proof option available)
Material of construction – painted mild steel, 304 and  316 stainless steel.

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