Sand Washing and Dewatering Screen Motor: Vibration Motor Selection

A dewatering screen is a high-frequency vibrating screen that drains water from washed sand through a polyurethane deck and discharges the sand at a stockpile-ready moisture; the electric drive on this screen consists of two vibration motors bolted to its body. In manufacturer catalogues the rating per motor is about 2.7–10.25 kW and the total of the two motors 5.4–20.5 kW [1][2]. The two motors must be the same model and turn in opposite directions; together they create the vibration. So a failure usually concerns a matched pair of motors, not a single motor.

The line's sand screw, bucket wheel and slurry pump use standard motors; they are briefly covered below. For an overview see Stone Crushing Plant Motors, and for the vibration motor range see Vibration Motors. Prices of standard motors are at Buy Electric Motors Online.

What is a dewatering screen and where does it sit in a sand washing line?

A dewatering screen is the last machine of the washing section. 0–5 mm sand from a tertiary crusher, a VSI or a natural pit is washed with water, clay and silt are removed, and the wet sand lands on this screen. The deck slopes slightly upwards; one manufacturer specifies a 5° incline [5]. While the vibration pushes the sand uphill, water drains down through the slots and the sand leaves as a cake that can be conveyed.

A typical layout is as follows:

• With a hydrocyclone: A slurry pump sends the sand-water mix to a hydrocyclone, which thickens it and drops it onto the screen. Loss of fine sand is reduced. In one example a 1600 × 3500 mm screen runs with 2 × 7.5 kW vibration motors and a 55 kW slurry pump [4].
• After a screw or bucket wheel washer: The screw or wheel lifts the sand out of the water and the screen removes the rest. Used for concrete and plaster sand, silica sand and coal preparation [1].

How it differs from a vibrating screen and a rotary screen

Vibrating screens in screening plants classify material by size (covered separately on the Vibrating Screen Motor page); their large versions also use a standard motor driving an eccentric shaft through belts. The job of a dewatering screen is not sizing but removing water: it is single-deck, its openings are very fine and its vibration frequency is high. A rotary screen (trommel), by contrast, turns without vibration and separates coarse material from clay during washing; the dewatering screen takes the fine fraction after it.

On the motor side the differences are:

• The vibration comes directly from the eccentric weights on the motor shaft; there are no belts, pulleys or reducer.
• The motor housing shakes together with the screen body; the motor works under constant shock and acceleration. That is why a standard three-phase motor cannot replace a vibration motor.
• The motor is in a wet environment: spray water, splashing slurry and the wash-down hose are right next to it.

How do vibration motors drive the screen?

The two vibration motors are bolted to the motor bridge above the screen body or to the side walls. Each motor has adjustable eccentric weights on both shaft ends. When the motors turn in opposite directions at the same speed, the horizontal forces cancel and the forces in one direction add up; the result is linear vibration. One catalogue states that the two motors initiate a linear motion [2]. The motors are not mechanically linked; the vibration of the screen body itself keeps them in step.

The eccentric settings of both motors must match; different settings pile the sand to one side. If one motor stops, the other shakes the screen unevenly and damages the springs, so the overload protections are interlocked.

Large screens may use a mechanical exciter instead: in one catalogue the 1.8–3 m wide units run on a 1 × 30 kW, 1000 rpm drive [1]; the motor type is confirmed with the screen manufacturer.

How many kW is a dewatering screen motor? Motor ratings on market models

A) Motor ratings found on manufacturer models

In this machine group, motor options of roughly 2.7–10.25 kW are found depending on the manufacturer's model and capacity [1][2]; these values are per motor, and a two-motor screen totals 5.4–20.5 kW [1]. The 55 kW motor of the cyclone feed pump is not the screen's rating; it belongs to a separate machine [4].

The main factor setting the rating is screen area and therefore sand capacity: from the smallest to the largest model of the same series, sand capacity rises from 10–40 t/h to 200–300 t/h and the per-motor rating from 2.68 kW to 10.25 kW [1]. Fine sand releases water more slowly than coarse sand; the same screen handles markedly fewer tonnes of fine sand [3]. Feed density also matters: in one catalogue capacities are based on a feed with at least 40% solids [1].

B) Matching motors in the DRG range

The 2.7–10.25 kW per-motor range lies within the DRG vibration motor range (0.12–15 kW); these motors are not in the online store, and model and price are set by quotation.

Worked example: 50 Hz vs 60 Hz, per motor and the line's total load

Neither a Bond work index nor a lifting calculation applies to this screen; the motor rating is read from the screen manufacturer's selection table. Three points need attention when reading the table.

• Per motor or total? "2 × 4.8 kW" means two separate 4.8 kW motors; the total is 9.6 kW [1]. When buying a spare, the per-motor value is the reference.
• Which frequency? One catalogue lists 2 × 2.88 kW at 50 Hz and 2 × 3.9 kW at 60 Hz for the same screen [2]; the ratio is 3.9 / 2.88 ≈ 1.35. Centrifugal force grows with the square of speed: for 1728 / 1440 rpm [1], (1728 / 1440)² = 1.44. So to run a motor from a 60 Hz sheet on a 50 Hz supply with the same force, the eccentric setting and motor selection are redone with the manufacturer.
• Where is the line's real load? On a cyclone unit the screen motors total 2 × 7.5 = 15 kW and the slurry pump 55 kW [4]; about 79% of the 70 kW total is in the pump. This split is taken into account when sizing the panel, cables and transformer.

Vibration motor checklist: wet environment, speed and connection

Collect this information before asking for a dewatering screen motor:

• Screen model and size; per-motor rating, speed and supply frequency (50 / 60 Hz).
• The centrifugal force (kN or kg) and eccentric setting percentage on the old motor's nameplate.
• Mounting dimensions: foot hole spacing, bolt diameter and number. Vibration motors do not follow IEC frame dimensions; the mounting plate depends on the model.
• Is the pair being replaced, or a single motor? If a single motor, it must match the remaining motor's force and speed.
• Wet environment: protection rating, terminal box gasket, cable entry, whether spray water hits the motor directly. The DRG vibration motor page gives the protection rating as IP65.
• Cable: because the motor shakes, a vibration-resistant flexible cable and a connection with strain relief are needed.

Speed and mounting

4-pole vibration motors (1440 rpm class at 50 Hz) are common on dewatering screens [1]; large mechanical-exciter units run at 1000 rpm [1]. The motor is bolted to the screen body by its foot plate; the bolts are tightened to a set torque and checked again after the first hours of operation. The exact mounting and bolt values come from the screen manufacturer's drawing.

Electrical connection

For the two motors to turn in opposite directions, one of them is connected with two phases swapped. With the wrong connection both motors turn the same way, the vibration is not linear and the sand does not move forward. Each motor is protected by its own overload relay and the relays are interlocked. Wiring work belongs to a qualified electrician.

Matching with DRG and quotation

DRG Motor is a manufacturer, supplier and seller of electric motors. Our standard motor range covers 0.25–11 kW in aluminium frames and 0.55–355 kW in cast iron; 1000, 1500 and 3000 rpm; 3-phase, 230/400 V or 400/690 V; B3, B5, B14 and B35 mounting (with an order note). The dewatering screen, however, runs only on vibration motors; the DRG vibration motor range covers 0.12–15 kW and is described on the Vibration Motors page. For the working principle see vibration motor working principle.

Request a quote for the right motor and current price. Vibration motors are not listed in the online store; send the screen model, motor nameplate and quantity via the contact page or WhatsApp and we will reply with a suitable model and price.

The other machines of a sand washing line run on standard three-phase motors that are covered by the DRG range. On sand screws, single-screw types use 15–45 kW and twin-screw types a separate 15–45 kW motor on each screw; the screw turns at 5–21 rpm, so the motor is connected through a reducer [6]. On a bucket wheel washer the wheel turns at 2.5 rpm and runs on a 5.5–7.5 kW motor [7]. On the cyclone feed pump the example value is 55 kW [4]. Example models for these machines:

DRG MOTOR motors are guaranteed against material and manufacturing defects for 2 years from the date of delivery (warranty certificate).

Dewatering screen motor: frequently asked questions

What is the working principle of a dewatering screen?

Two vibration motors turning in opposite directions vibrate the screen linearly. On the upward-sloping deck the sand slowly moves forward and forms a cake while water drains through the fine slots.

If one of the two vibration motors burns out, is replacing only that one enough?

The new motor must be the same model, at the same speed and the same centrifugal force as the remaining motor, and the eccentric settings must be equalised. If the motors have run for a long time, replacing them as a pair, taking bearing condition into account, is often the safer choice.

Can a normal three-phase motor replace a vibration motor?

No. A vibration motor is a special motor with eccentric weights and heavy-duty bearings built for shock loads; a standard motor can neither carry this load nor produce the vibration.

How many kW is a sand screw washer motor?

In the catalogue reviewed, single-screw washers use 15–45 kW and twin-screw washers 2 × 15 … 2 × 45 kW [6]. The exact value depends on screw diameter, length and sand capacity.

Send us the screen model, a photo of the motor nameplate and the quantity, and we will define the vibration motor pair and the other motors of the washing line together. Contact: WhatsApp or phone +90 (542) 666 11 11; for written requests [email protected] and the contact page. For standard motors and current prices: Buy Electric Motors Online.

Sources

1. Metso – Opti-Flo screens and feeders range (Toromont Cat kopyası) – HF dewatering screens 2 × 2.68 … 2 × 10.25 kW vibrator motors, 1440 rpm (50 Hz); large LH-DW units ML80 exciter, 1 × 30 kW, 1000 rpm.
2. MEKA – MDS Series Dewatering Screens (katalog) – MDS 1224 / 1824 / 1840: 2 × 2.88 / 2 × 7.35 / 2 × 6.1 kW at 50 Hz; 2 × 3.9 / 2 × 6.6 / 2 × 6.4 kW at 60 Hz.
3. Astec – Dewatering Screen Spec Sheet – DWS 38 … DWS 816: 2 × 3.9 … 2 × 12.7 HP (60 Hz) vibrating motors; fine sand 20–121, coarse sand 65–403 t/h.
4. Constmach – CDS-1635 Dewatering Screen & Hydrocyclone – 1600 × 3500 mm screen, 2 × 7.5 kW vibrator motors, 55 kW slurry pump, 100–150 t/h.
5. Fabo – DSHC-1840 Dewatering Screen – 2 × 9 kW vibro motors, polyurethane deck inclined at 5°.
6. MEKA – MFW Series Fine Material Washers (katalog) – single screw 15–45 kW, double screw 2 × 15 … 2 × 45 kW; screw speed 5–21 rpm.
7. Constmach – CBW-1000 Bucket Wheel Sand Washer – Ø3000 mm bucket wheel, 2.5 rpm, 7.5 kW motor, 110–120 m³/h (CBW-800: 5.5 kW).