Stockpile and Stacker Conveyor Motor

A stacker conveyor takes the finished product of a crushing and screening plant to the stockyard and, by raising its boom, builds tall, wide stockpiles; on radial models the boom swings in an arc around a pivot, and on telescopic models it can also extend and retract. In this machine the electric motor first of all pulls the belt from the head pulley: in manufacturer spec sheets the belt motor of 15–30 m radial stackers falls between 7.5 and 37.3 kW [1][3]. Telescopic models add a second belt motor, a hydraulic power pack motor and wheel travel motors [4]. So the answer to "how many kW is a stacker motor?" can only be given once you know which motor (belt, stinger belt, hydraulic or travel) is being replaced.

Suitable belt motors and current prices are among the 120 models at Buy Electric Motors Online. General overview of all plant motors: Stone Crushing Plant Motors.

What is a stacker conveyor and where does it sit in the plant?

A stacker is not a crushing stage; it receives the product leaving the primary, secondary or tertiary crusher and the final screen. It turns material such as 0–5 mm sand, chipping sizes, washed gravel and limestone into piles ready for truck or loader loading. A separate stacker is usually used for each product size coming off the screen.

There are three basic layouts:

• Fixed stacker: Does not move; builds a single conical pile.
• Radial stacker: The tail end is attached to a pivot and the boom travels in an arc on a wheeled undercarriage. The larger the arc, the more material is stored on the same ground: the spec sheet of a 30.5 m radial stacker gives 12,439 t for a 90° pile and 31,559 t for a 270° pile [3].
• Telescopic stacker: A second belt (the stinger) moves in and out inside the outer boom; the pile is laid down in layers and segregation of fine and coarse particles is reduced [4][5].

Applications: quarry product stockpiles, piles where washed sand drains, aggregate yards of concrete plants, mine and port stockyards; all outdoors, in dust and rain.

How it differs from an in-plant belt conveyor: a group of motors, not one

In-plant belt conveyors have a fixed incline and usually a single drive (Belt Conveyor Motor page). On a stacker the boom angle changes in operation, the machine travels and the long boom catches the wind in an open yard; so the number of motors grows.

• Belt drive motor: The main load. It lifts and carries the material to the end of the boom.
• Stinger belt motor (telescopic type): Drives the inner belt separately; in one telescopic spec sheet the main belt runs on a 29.8 kW motor and the stinger on a 22.4 kW motor [4].
• Hydraulic power pack motor: Turns the pump that feeds the boom lift cylinders, the axle raise and, on telescopic types, the boom extension winch. One sheet offers a 5.6 kW electric/hydraulic power pack option [1]; on the telescopic example this unit is 15 HP [4].
• Travel motors: Provide the radial movement. One manufacturer offers a 1.5 kW electric power travel option [2]; on the telescopic example each of the four wheels has a 2 HP planetary drive and the machine can travel on a 4% grade [4].

How does the motor drive the stacker?

On most radial stackers the belt drive is at the head pulley at the top end of the boom. The arrangement in the sheets reviewed is the same: a totally enclosed fan-cooled (TEFC) induction motor, V-belts and sheaves, a shaft-mount reducer fitted on the pulley shaft and a backstop inside the reducer [1][2][3]. The backstop prevents the belt and material from running back when the inclined boom stops loaded; so if the motor's direction of rotation is wired the wrong way on a reducer with a backstop, the motor cannot start, the current rises and the protection trips.

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

A) Motor ratings found on manufacturer models

In this machine group, motor options of roughly 7.5–55 kW are found depending on the manufacturer's model and capacity [1][5]. Auxiliary motors are on separate rows; a "total power" figure is not the rating of one motor.

The two main factors that change the rating are clear in the table. For the same 907 t/h capacity, when boom length rises from 15.2 m to 30.5 m the belt motor grows from 22.4 kW to 37.3 kW [1][3], because the belt is longer and the material is lifted higher. At the same 30.5 m length, when capacity rises from 227 t/h to 907 t/h the motor goes from 11.2 kW to 37.3 kW [3]. Capacities are based on a bulk density of 1.3 t/m³ [1]; heavier material needs more power.

B) Matching motors in the DRG range

The whole 7.5–55 kW range and the 1.5–5.5 kW auxiliary motors are covered by DRG's 4-pole (1500 rpm) range. Outside it: the hydraulic motor of a hydraulic belt drive, the wheel planetary gearboxes and port- or mine-scale stacker-reclaimers.

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Worked example: why does the belt motor work harder as the boom rises?

On a conveyor the power supplied by the motor splits into two parts: the power needed to lift the material, and the friction and losses of the belt over idlers, pulleys and the belt-reducer drive. The lifting part comes from a simple relation: P_lift = Q · H / 367 (P in kW, Q in t/h, H lift height in m).

Example: on a 30.5 m radial stacker with a 762 mm belt and a capacity of 454 t/h, the belt motor in the sheet is 18.6 kW [3]. The feed point is at 1.6 m and the highest discharge point at 10 m [3].

• Boom at the top position: H = 10 − 1.6 = 8.4 m. Boom angle about 16°. P_lift = 454 × 8.4 / 367 ≈ 10.4 kW.
• The rest of the motor rating: 18.6 − 10.4 ≈ 8.2 kW. This share covers idler and belt resistance, pulley and belt-reducer losses and the margin for starting with a loaded belt.
• Boom at the bottom position (discharge 4 m [3]): H = 2.4 m, P_lift ≈ 3.0 kW. In this position the motor runs clearly at part load.

The belt motor is chosen for the steepest boom position and for starting with a loaded belt. The DRG-180M-4 (18.5 kW) corresponding to this rating has a rated torque of 120.2 Nm and a starting torque ratio of 2.0; with direct-on-line starting it gives about 240 Nm of starting torque. With star-delta starting, starting torque drops to about one third, around 80 Nm; this is below rated torque and may not get a belt that stopped loaded on a steep boom moving. For a comparison of methods see the star-delta starting page.

Stacker motor selection checklist, speed and mounting

Collect this information before asking for a motor; the list is specific to stackers:

• The duty of the motor to be replaced: belt, stinger belt, hydraulic power pack or travel.
• The old motor's nameplate: kW, rpm, IEC frame, voltage and frequency (50 Hz or 60 Hz).
• Boom length, belt width, capacity, highest discharge height and bulk density of the material.
• Sheave diameters and reducer ratio; whether the reducer has a backstop and its free-running direction.
• Starting condition: can the belt stop loaded, the starting method, sequence interlocking (the stacker must start before the conveyor feeding it and stop after it).
• Length and cross-section of the cable feeding the moving machine; voltage drop on a long run (motor cable size calculator).
• Environment: open yard, rain, dust; terminal box orientation and cable entry facing downwards.
• Wind: the long boom takes side loads and burdens the travel motors during radial movement; the machine builder calculates wind load, and travel and boom lift motors are not undersized.

Speed and mounting

Four poles (1500 rpm) are common for the belt motor; the belts and reducer bring the pulley speed down. If a 6-pole motor is chosen, the reducer or sheave ratio must change accordingly; otherwise belt speed and capacity drop. In a belt-driven layout the belt motor is fixed by its feet (B3) to the motor base at the boom tip. On the hydraulic power pack the pump is usually attached to the motor flange with a bell housing (B5 or B35); on travel drives the planetary reducer input is flanged. The exact type comes from the machine manufacturer's drawing; at DRG the mounting type is specified with an order note.

Starting

In the DRG range, motors of 4 kW and above are wound for 400/690 V and are suitable for star-delta starting on a 400 V supply. With a loaded belt on a steep boom a soft starter or VFD is considered; in the telescopic example each motor has its own starter [4]. The connection must be made by a qualified electrician.

Matching DRG motors

DRG Motor is a manufacturer, supplier and seller of electric motors. Our 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). For stacker belt motors and auxiliary motors the following models stand out:

DRG-132S-4 is for the hydraulic power pack and DRG-90L-4 for the travel class; the others are belt motors. For general principles see electric motor selection for conveyors and belt lines, and for the role of the reducer see the role of a gearbox in an electric motor.

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

Stacker belt motors

• DRG-132M-4 – 7.5 kW – 1460 rpm – 132M cast iron
• DRG-160M-4 – 11 kW – 1465 rpm – 160M cast iron
• DRG-180M-4 – 18.5 kW – 1470 rpm – 180M cast iron
• DRG-200L-4 – 30 kW – 1475 rpm – 200L cast iron
• DRG-225S-4 – 37 kW – 1485 rpm – 225S cast iron

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Stacker conveyor motor: frequently asked questions

How many kW is a radial stacker belt motor?

In the sheets reviewed, the belt motor of 15–30 m radial stackers is between 7.5 and 37.3 kW [1][3]. The exact value depends on belt width, boom length, capacity and the highest discharge height; on replacement the old motor's nameplate is the reference.

How many motors does a telescopic stacker have?

At least two belt motors (main and stinger), one hydraulic power pack motor and wheel motors for radial travel. In the example reviewed these are 29.8 kW, 22.4 kW, 15 HP and four 2 HP drives [4].

Can a 50 Hz motor be fitted to an imported 60 Hz stacker?

Yes; but a 1500 rpm motor instead of 1800 rpm lowers belt speed by about 17%, so the sheave ratio is changed to keep capacity.

Is the hydraulic power pack motor chosen like the belt motor?

No. It is chosen for the pump's flow and pressure, is usually flange-mounted and runs intermittently; its nameplate value and flange size are the reference.

Send us the spec sheet or a photo of the motor nameplate and we will finalise the right motor together. Phone +90 (542) 666 11 11, e-mail [email protected], contact page. For all models and current prices: Buy Electric Motors Online.

Sources

1. Astec – Radial Stacker 50' [15.2 m] Spec Sheet – 15.2 m; belt motor 7.5–22.4 kW, 5.6 kW hydraulic power pack option.
2. Astec – Radial Stacker 80' [24.4 m] Spec Sheet (distribütör kopyası) – 24.4 m; belt motor 7.5–29.8 kW, 1.5 kW travel.
3. Astec – Radial Stackers 100' [30.5 m] Spec Sheet – 30.5 m; belt motor 11.2–37.3 kW, discharge 4–10 m.
4. Superior – 36" x 150' Portable TeleStacker Conveyor (Mellott Company) – telescopic; belt motors 40/30 HP, 15 HP hydraulic, 4 × 2 HP wheels.
5. Polygonmachine – PTRC Series Telescopic Radial Stackers – 300–1000 t/h; 22–55 kW.