Agricultural Bucket Elevator Selection Tips |
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| All too often, bucket elevators are selected
strictly on the basis of price. While price may prove to be a major consideration in
some cases, it should never be used as the sole criterion for decision making. In
addition to differences in price, there may also be broad margins of differences in
the design, materials and construction of even "standard" bucket elevators.
The following article will present basic criteria and checkpoints which can be used to: Due to space limitations, this article will be limited to the proper selection of standard, commercial, centrifugal discharge type bucket elevators, used to elevate dry grain. The following points are offered only as general guidelines and do not cover the particulars of either government regulations or unusual application problems. Is This The Proper Equipment For The Job? Because of the different characteristics of the many bulk materials being handled and the variety of circumstances involved, there are many types of conveyors in use. The bulk material conveying chart can serve as a guide to the different types of conveyors manufactured at Union Iron Works for handling bulk material. The final selection of a conveying system must be based on the general characteristics of the material, flowability, volume required, elevating or horizontal distances required. Union Iron Works has designed, furnished and installed complete material handling systems. This method of handling a project assures the owner of one reliable source for engineering, equipment and field erection, as well as a single source for a complete system.
Analyze Bucket Elevator Requirements As with the purchase of any major piece of equipment, the final selection of a bucket elevator should be made only after careful consideration of all factors affecting the application. Specific requirements should be established only after the total materials handling system has been analyzed. System analysis should give consideration to factors such as:
Evaluation of the points above may greatly alter initial conceptions of specific bucket elevator needs. Future requirements, flow limiting factors and the possibility of increased usage versus bucket elevator location within the system can all prove to be major determinants in the final selection. Provide "Rule of Thumb" Engineering Information As with all other products, the more the buyer knows about bucket elevators, the more qualified he is to purchase the one right for his particular operation. The points below are simple rules of thumb, which can nevertheless offer better understanding of the more significant points of bucket elevator design. Horsepower Requirements To determine horsepower requirements, multiply the bucket elevator height by the capacity by a factor of .0000379.
By rounding to the next highest standard electric motor, a 25 HP motor should be sufficient for this particular application. Note: the factor used above includes a 25% safety margin. Head Pulley Diameter The method of determining the correct head pulley diameter for a given application is a true bone of contention among bucket elevator manufacturers. The most commonly used rule of thumb is that the minimum diameter of the head pulley should be five times the horizontal measurement between the back of the bucket and the front lip, or projection.
The selection of the correct head pulley diameter is crucial for proper discharge of the bucket and can also be of major importance in applications where the bucket elevator is extremely tall or is used to elevate high capacities. Commonly used head pulley diameters are 24", 30", 36", 42", 48", 60" and 72". Note: Head pulleys should always be equipped with high quality lagging materials. Belt Speed There is an optimum range of belt speeds for each pulley size and each bucket size. Operations at speeds outside of the optimum range can cause improper bucket discharge, down legging and excessive damage to materials being elevated. The chart below shows the range of standard pulley diameters, belt speeds and bucket sizes, plus the theoretical capacities commonly used in standard bucket elevator designs.
Note: The above capacities are calculated using K.I. Willis Type "C-C" buckets at mid-range of belt speed and at 75% bucket fill. The use of other type buckets and belt speeds will alter these capacities accordingly. Bucket Spacing Buckets should be spaced on the belt at equal intervals. The minimum distance between buckets should be atleast two inches greater than the bucket projection.
Casing Size and Clearance Clearance for belting and buckets is essential. The higher the bucket elevator, the more critical this clearance becomes. The following general rules of thumb will help you calculate the minimum measurements needed for belt, pulley face and leg casing widths and leg casing depths. Belt Widths = Bucket Width + 1 inch minimum. These rules not only allow for slight misalignment in installation, but also help the belt "work in" and find the center of the pulley. For sizing leg casing, the width should be a minimum of 2 inches larger than the face width of the pulley. Leg casing size should also allow for a minimum of 4 inches lip clearance. The width of the leg casing should be atleast 2 inches wider than the width of the pulley face. The depth of the casing is somewhat more related to the height of the lift and the bucket projection, but should be a minimum of 5 inches more than the bucket projection. Systematically Evaluate Price Quotation It's always good practice to secure more than one quotation on any major purchase; however, making an "apples to apples" comparison between quotes can be difficult. To make comparisons easier to evaluate, request that all quotations provide information on the eleven points listed below. These points not only provide an exact description of the bucket elevator being evaluated, but also make comparisons between different bucket elevators a logical, systematic process.
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