What is a Skip Hoist?

A skip hoist is a continuous conveying machine that uses a series of hoppers evenly fastened to endless traction members to vertically lift materials. The skip hoist uses a series of hoppers fastened to traction chains or tapes to transport bulk materials upward in the vertical or near-vertical direction.

This article will give you a detailed introduction to what a skip hoist is, from its classification, structure, common types, installation requirements, working principles, common failures, and handling methods.

Here is the outline.

Classification of skip hoist

There are many ways to classify skip hoists, generally

(1) according to the different installation methods, it can be divided into vertical, inclined, and vertical horizontal types.

(2) according to the different unloading characteristics, it can be divided into centrifugal, centrifugal-gravity, and gravity types.

(3) according to the different loading characteristics, it can be divided into hollowing and inflow types.

(4) according to the different forms of traction components, it can be divided into belt and chain types (plate chain, ring chain)

(5) according to the different forms of hopper, it can be divided into deep bucket, shallow bucket, and scale bucket (triangular bucket or trapezoidal bucket) types.

Structure of skip hoist

skip hoist
Vertical tape skip hoist

1. adhesive tape

2. Hopper

3. Drive roller

4. Tensioning roller

5. The upper part of the casing

6. The middle section of the casing

7. Several seats of the casing (seat plate)

8. Observation holes

9. Drive unit

10. Tensioning device

11. Guide rail plate

Three types of common skip hoist

TypeTD typeTH typeTB type
Structural featuresUse rubber belt as traction memberUse forged ring chain as traction memberUse plate type sleeve roller chain as traction member
Unloading FeaturesDischarge by centrifugal or hybrid methodDischarge by gravity or hybrid methodDischarge by gravity method
Applicable conveying materialsLoose density p <1.5t/m³ of powder, granular, small lumps of non-abrasive, semi-abrasive materialsLoose density p <4.5t/m³ of powder, granular, small lumps of non-abrasive, semi-abrasive materialsLoose density p <2t/m³ of medium and large lumps of abrasive materials
Applicable temperatureThe temperature of the conveyed material shall not exceed 60℃, and the temperature shall not exceed 200℃ if heat-resistant rubber belt is used.The temperature of the conveyed material shall not exceed 250℃The temperature of the conveyed material shall not exceed 250℃
ModelTD100, TD160, TD250, TD315, TD400, TD500, TD630TH315, TH400, TH500, TH630
Lift heightAbout 4-40mAbout 4.5-40mAbout 5-50m
Delivery volume4-238m³/h35-185m³/h20-563m³/h

Installation requirements of skip hoist

1、 The supporting surface of the lower section of the skip hoist must be located on the horizontal surface of the foundation.

2、 The upper drive shaft and the lower tensioning shaft of the skip hoist should be in the same vertical plane, and the center line of the two shafts should be parallel to the horizontal plane.

3、 The flange connection of the middle casing should not have a significant misalignment. Asbestos gasket or waterproof canvas can be padded between the flanges to ensure sealing.

4、 The centerline of the lower section, middle and upper section of the skip hoist should be on the same vertical line. The deviation of verticality should not exceed 1 mm in 1-meter length and the cumulative deviation of total height should not exceed 8 mm.

5、 The position on the traction member of the hopper should be correct and fastened reliably. In operation, there should be no deflection and collision with the casing.

6、 The installation position of the deflector plate of the skip hoist must meet the requirements of the drawing.

7、 After adjusting the screw tensioning device, it should make the traction member have uniform and necessary tensioning force for normal operation. In order to make enough tensioning stroke in operation, the remaining tensioning stroke should be not less than 50% of the full stroke.

8、 The axis of the high-speed shaft of the reducer and the axis of the motor should be parallel to each other and in the same horizontal plane; the axis of the low-speed shaft and the axis of the skip hoist drive shaft should be in the same horizontal line, and the maximum parallel offset should not exceed 0.2 mm, and the maximum axis intersection angle should not exceed 40′.

9、 The skip hoist should be installed with lifting equipment, lifting capacity of not less than 2 tons. The distance between the bottom of the crane rail and the centerline of the drive shaft is generally 2~2.2 meters.

10、 The middle of the skip hoist should have a middle support device to prevent deflection. The distance between the support points is not more than 8 meters. The uppermost support point should be as close to the head as possible.

11、 The skip hoist should be maintained as required.

Working principle of skip hoist

On the flexible traction member, a number of steel hoppers are installed at certain intervals. The closed traction member is rolled around the upper and lower rollers, which are tensioned by the tensioning device on the base through the redirecting wheel and driven by the upper drive wheel. The material is fed from the lower part, and the hopper lifts the material to the upper part. When the hopper goes around the upper roller, the material is thrown outward by gravity and centrifugal force and sent to the silo or other equipment through the discharge ramp. The elevator forms an endless closed loop with a rising loaded branch and a falling unloaded return branch.

Common failures and handling methods of skip hoist

FailuresCause of failureHandling methods
Shuffling 1. Clogging of the downcomer funnel
2. Lower material silo full
1. Stop and check the downcomer funnel
2. Change to another storage silo
Blocking material1. Too much material at the feeding port
2. The hopper is broken3. The chain is too loose
1. Reduction of feed or suspension of the feed system
2. Repair or replace the hopper
3. Tighten the chain
Damaged lower rolling bearing1. Improper adjustment of the traction member
2. The length of the two traction members is not the same
1. Readjustment
2. Correct the length
Traction member slippage1. The traction member is too long
2. Excessive wear of the upper chain
3. Excessive wear of the traction member
1. Adjust the screw rod
2. Replace
3. Replace
Traction member or hopper pulling bad, stuck1. There are hard and tough debris mixed in the material
2. Loose bolts of traction members and hopper
3. Traction members are too loose or too tight
4. Too much material is added
1. Stop to take out debris to repair or replace damaged parts
2. Stop to tighten the bolts
3. Adjust the screw rod
4. Adjust the feeding volume

After reading this article, I believe you have a certain understanding of what a bucket elevator is. If you have any questions or want to know more, please leave a comment and let me know.

Also to read:

Skip Hoist Type Concrete Batching Plant-Why and How to Choose

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