TPI - Bucket Elevators for Bulk Material Handling

Bucket Elevators are designed to lift material vertically and are, by far, the least expensive option for elevating bulk materials. There are two basic styles; Centrifugal Discharge and Continuous Discharge; either of which can have buckets mounted on a belt or a chain. (Please see “Bucket Elevator Types” in the down loads section for more illustration.)

Centrifugal Discharge units have buckets mounted at wide intervals and are designed to dig or scoop dry, granular, free flowing materials that are smaller than 1 1/2” in size (maximum lump size varies by bucket size).from the boot, or the bottom of the casing. They operate at higher speeds, which will throw the material from the bucket as it comes over the head pulley (or sprocket) due to centrifugal force and are capable of handling up to 15,000 cubic feet per hour. (Common bucket sizes are 6x4, 8x5, 10x6, 12x7, 14x7, 16x8, 18x8, 18x10 and 20x10.)

A sub-style of Centrifugal Discharge elevators is called a “Cement Mill” unit; it utilizes style “AC” style buckets, which are designed to handle the dry, fine, free-flowing materials that are typically found in a cement plant application. Cement Mill elevators are usually chain mounted and can handle up 15,000 cubic feet per hour with standard “AC” buckets and 12,000 cubic feet per hour “ACS” style (saddlebag) buckets. (Common bucket sizes are: 12x8, 16x8, 18x10, 20x10, 24x10 and 27x12.)

Continuous Discharge units have buckets spaced very closely together and are designed to handle larger lump sizes or materials that are easily broken. Therefore, they generally do NOT dig or scoop material, but rather the material is loaded directly into the buckets. They operate at much lower speeds, allowing the material to gently slide from the buckets, rather than be thrown. They can deliver up to 25,000 cubic feet per hour. (Common bucket sizes are: 8x5, 10x5, 10x6, 10x7, 12x6, 12x7, 12x8, 14x8, 16x8, 18x8, 18x10, 20x12 and 24x12.)

A variation on the Continuous Delivery bucket elevator is the “Super Capacity” style, which has larger buckets mounted between two strands of chain. This configuration can handle 15,000 cubic feet per hour, or more. (Common bucket sizes are 12x8, 14x8, 16x8, 16x12, 20x8, 20x12, 24x12, 30x12 and 36x12.)

Bucket Elevators are highly efficient and have the added benefit of being dust-tight and weather-tight. They also lend themselves to harsh applications, such as; highly abrasive materials, corrosive materials, elevated temperatures and potentially explosive materials.

As an alternative to bucket elevators, a Vertical Screw Elevator (VSE) is an option for a fairly small capacity with not much lift needed. They actually take up the least amount of floor space, but require quite a bit more power and are not nearly as self-cleaning as a bucket elevator. (Common sizes are 6”, 9” 12” and 16”.)

Elevator Buckets can be belt mounted or chain mounted. Here are some of the differences:

• Less costly
• Quieter
• Smooth running
• More Corrosion resistant
• Lighter hanging weight means a smaller head shaft and bearings
• More wear resistance in highly abrasive applications
• More likely to slip if not properly tensioned or lagging is worn or wet
• More difficult to splice or remove excessive belting
• Bucket bolts more likely to pull out
• Less tolerant of boot flooding
• Complete Belt is harder to install
• Bucket spacing significantly more flexible

• More costly
• More Noise
• Tend to vibrate and “clank”
• Stronger
• Higher hanging weight means a larger head shaft and bearings
• Higher material and ambient temperature tolerance
• Positive engagement w/ no slippage (traction wheels subject to slippage)
• Easy to remove excessive chain links
• Bucket bolts unlikely to pull out
• More tolerant of boot flooding
• Complete chain easier to install
• Bucket spacing must match chain pitch multiples