Slope, Flow and Loads for Gravity Conveyors

Install Gravity conveyors on declines so that the infeed side sits higher than the end of the line for smooth product flow. This is one of the easiest ways to move products quickly and economically. How can you set up your gravity conveyor for optimal product flow?

Factors for product flow

Speed and flow

1. Infeed and discharge elevations: These are the fundamental heights of the conveyor at the top (where product enters) and bottom (where the product stops). The steeper this slope, the faster product can flow.
2. The acceleration effect: The acceleration effect of spinning roller or wheel that’s still moving after a preceding box has rolled across it affects flow speeds.
3. Flow design: Boxes and other loads move faster in straight lines. Adding curves or turns reduces flow.
4. Speed: too fast, too slow If your conveyor flows a little too well, you can adjust the pitch or use retarding plates to manage roll speeds. You can also add end stops for managing the end of the line. if the conveyor flows slowly, you can increase slope angle to speed things up.

Conveyor type and specifications

1. Conveyor type (roller or skatewheel): Items flow faster on skatewheel than they do on gravity roller conveyors. Rollers work better for poor loads and more types of loads.
2. Are bearings grease-packed or clean? Grease packed bearings tend to roll slower.
3. Load weight: Specifying conveyors so that they fit the weight of your load promotes good product flow. Rule of thumb is that the same type of load, on the same conveyor, at the same slope, will move faster when it’s heavier. Some very light loads will not move at all. Some very heavy loads may move too fast. A tote that weighs 10 pounds requires more slope than one that weighs 50 pounds.
4. Line length: Cartons may accelerate on longer runs. Make sure they don’t move too fast for the operation or end of line process.

Load characteristics

Firm, smooth loads flow better. Difficult loads tend to require rollers, and move slower. Very difficult loads–saggy, damaged, or inconsistent– are harder to convey. A firm carton conveys differently than a tote of the same weight, placed on the same slope. The differences are more pronounced when load bottoms aren’t consistent, rigid or easy to convey. Bags or other loads with irregular conveying surface will be harder to move than any smooth or rigid surface.

Test conveyor slope before operation

Always test product flow and slope before you begin using the conveyor. It’s relatively easy to adjust pitch before the conveyor goes into operation and you’re dealing with live loads. Be sure you know the largest/smallest, lightest/heaviest load you’ll be conveying.

Gravity skatewheel conveyors vs. gravity roller conveyors

Pitch, angle and speed

• Skatewheels need less pitch to convey the product in a decline situation than rollers.
• Lightweight loads and empty cartons flow easier on the skatewheel conveyor because it takes less force to start several wheels in motion than a roller.
• Skatewheels flow faster because they require less energy to move the load.

Skatewheels help maintain product orientation

Due to the natural differential action of skatewheel conveyors, conveyed products better maintain orientation while moving. This is especially desirable if the product moves around a curved section. As the load negotiates the curve, the skatewheels provide this differential action just as a tapered roller curve. Because each wheel turns independently, skatewheel conveyor is excellent for curves in a conveyor line.

Roller conveyors handle a much larger variety of loads and load types than skatewheels

Drums, pails, and products with uneven or irregular bottoms don’t convey well on skatewheel conveyor — for those, specify rollers. Skatewheel loads need a smooth, solid and flat surface. Because they use plain ball bearings, use skatewheel conveyors should in clean, dry, dust-free environments.

Product type and size

Consider product size and characteristics when you specify gravity conveying systems

• Skatewheels require 3 axles and 10 wheels under the product bottom at all times.
• You’ll need at least 3 rollers beneath any load to properly flow and support it.
• Skatewheel is lighter duty and generally used in light duty installations.
• Rollers handle heavier, irregular loads. Check your load vs. the conveyor’s listed capacity.
• Skatewheels extend above the conveyor frame to permit loads to overhang the sides, Don’t allow the width of the load to exceed the conveyor width by more than 25%.

More information

• Read our full Guide to Gravity Conveyors
• Product specifications: Straight & curve gravity conveyors
• Product specifications: Flexible roller and flexible skatewheel systems

Video: a guide to skatewheel selection

Tags: shipping docks, skate wheel conveyors, Roller Conveyors

The roller is an important component of the conveyor. According to the different conditions of use, the roller can be divided into more than ten kinds, mainly: the load-bearing side roller, which can be divided into single roller, double roller, three-section roller, five-section roller and Seven-section rollers, etc.; idler side rollers include single roller, double roller and three-section rollers, etc.; there are buffer rollers at the reprinting place; transition rollers in the transition section; self-aligning rollers; cleaning rollers, etc. According to the form of the conveyor bracket, there are fixed brackets and hanging brackets. From the structure of the roller itself, it is mainly divided into the sealing lubrication method, the structure of the roller shaft and the difference of the roller bearing (except for the special purpose roller). In terms of sealing and lubrication, there are contact sealing and gap sealing, one-time lubrication and regular lubrication. From the structure of the roller shaft, there are optical shafts (guaranteed by machining accuracy), hollow shafts, stepped shafts, and so on. From the bearing form, there are centripetal ball bearings, deep groove ball bearings with large clearance and tapered roller bearings. There are many types of rollers on the market. Which type of roller is more suitable for the needs of users? It is necessary to use scientific calculation and analysis methods so that users can get the most economic benefits from them. Let's analyze this problem from a qualitative perspective. 1. Working environment and status of rollers The working environment and status of rollers should explain the following issues: (1) The type of material conveyed by the conveyor, the particle size distribution of the material, the dynamic accumulation angle, the density, the hardness, the moisture content of the material, and the various Corrosion degree of corrosive medium, etc.; (2) The working environment of the loading conveyor mainly includes temperature (maximum and minimum temperature), humidity of air, content of corrosive medium, size of working space, whether it is easy to repair and maintain, etc.; (3) ) The service life of the conveyor; (4) Some other basic parameters of the conveyor, such as the operating speed of the conveyor belt, the hourly capacity of the loading conveyor, the line condition of the loading conveyor, the type of support and the working system of the conveyor (daily operating time and One-time continuous operation time) and so on. 2. Calculation of roller load The roller load is divided into static load and dynamic load, and can be divided into radial load and axial load according to the direction of action. The research on the calculation of the load of the roller is not perfect, and the law of some loads is still unclear. The static load calculation of the idler mainly considers the positive pressure of the material and the tape, and the tension of the tape should also be considered in the bending section, especially in the convex-concave arc section. When analyzing the force of trough rollers, the main problem is the distribution of the load on the three rollers, especially in the convex arc. At present, most calculations regard the middle roller as the maximum force, which is based on 70% and 70% of the weight of the material. 40% of the weight of the tape is calculated, but the force of the two bearings after the side roller is loaded is not equal, and there is a relatively large axial force. The dynamic load of the idler mainly includes: (1) the dynamic load generated by the eccentric rotation of the idler roller shell; (2) the dynamic load caused by the interaction between the eccentric rotation of the idler and the tape; (3) the impact on the idler during the movement of the tape and the material (4) The dynamic load caused by the belt's lateral bending vibration and flapping the idler; (5) The dynamic load caused by the belt tension change on the transitional section and the bending section idler; (6) The high-speed running tape passes through the idler When rolling, the deformation of the material and the tape exerts a force on the side roller, especially when the material contains large pieces, the impact force is great; (7) The roller is subjected to the impact dynamic load of the falling material at the transfer location. The correct calculation of these loads is very important for selecting rollers and estimating the service life of rollers. 3. Estimation of the life and reliability of the roller. The life and reliability analysis of the roller is very important to the user. This work should be jointly completed by the design unit and the manufacturer of the roller, and an analysis report can be provided to the user. 4. The strength of the roller manufacturer A very important factor that affects the quality of the roller is the technical force, technical equipment, scientific management and good service consciousness of the roller manufacturer, which is very important to users. manufacturers should be able to provide users with complete technical services, from design calculations, roller selection and economic and technical analysis to complete machine design. Judging from the current situation at home and abroad, our advantages in this area are more prominent.

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