General Practices & Preventative Maintenance for your Pellet Mill The pellet feed industry has grown to cover a wide range of animal feeds. Studies have shown that feeding animals pelleted feed will induce more nutrients into their diet, will make it easier to digest, and will show better gain results while reducing feed waste. Jacobs Corporation understands this application and is dedicated to provide customers with high quality products to make their pelleting process more efficient. The following preventive maintenance report illustrates important practices that should be followed to prolong the life of your dies and roll shell assemblies to reduce production failures and down time. Safety Safety is an important aspect for any operation process. General personal protective equipment (PPE) for the pellet mill industry includes a hard hat, gloves, safety glasses, steel toe shoes, and ear plugs. Additional equipment may be required by your company. Please review safety guideless with your company before operating equipment. Image 1: Personal Protective Equipment -PPE Installing a new die When installing a new die, it is important to follow proper preventative maintenance procedures to prolong the life of your dies and verify when replacement parts need replacement. Such replacement parts include die clamps, wear rings, key way, and the pellet mill quill. Cleanliness is an important aspect while operating your pellet mill. Having your pellet mill clean and free of debris will result in better contact areas between the die, die clamps and wear ring.
As mentioned before, cleanliness is a key aspect when installing a new die. Removing dried up feed from contact areas between the pellet mill and your dies will provide better fitment. The following images illustrate key points to consider: 1. Use a wire brush to remove debris from around the quill and any contact surfaces. 2. Check wear stage on the quill with a quill gauge. Once quill is past second stage wear it will not provide support to the die and will induce stress on the material. At this point the quill needs to be replaced or re-worked to prevent possible die breakage. Instructions on how to check wear stage are located on pages 7 and 8. Contact pellet mill manufacturer when ordering a new quill. 3. Periodic inspection of the key way is recommended. The key way is for location purposes and any damage or wear will induce movement of your die. Once it is worn out then replacement is recommended. 4. Wear rings are an essential component to providing adequate support to the dies. It is recommended to replace them at least every 3 rd die or every year and a half. Replacement practices depend on how often dies are replaced. Image 2: Pellet Mill Quill - Cleanliness Image 3: Replacement of Key Way Image 4: Replacement of Wear Ring
Once your contact surfaces are clean and replaceable parts have been inspected for wear it s time to install your new die. The following proper care rules are essential to prolong the life of your die: 1. Do not strike dies with a hammer, if additional work is required to properly mount the new die use a rubber hammer. 2. Note any fitment issues. A Loose fitment can be due to a worn quill or wear rings. Report such issues to Jacobs Corp. 3. As mentioned before, die clamps should always be checked for stage wear when installing a new or replacing a die. A clamp gauge needs to be utilized to check for stage wear, see pages 5 and 6 for instructions. Use a rubber hammer when mounting die clamps. 4. General recommended torque on die clamps is 350 ft/lb. Please refer to your pellet mill s manual to review their requirements on applied torque. Image 5: Mounting a New Die Image 6: Mounting Die Clamps Match each corresponding letters (A to A, B to B, C to C) when mounting die clamps for proper fitment and support. Letters should be facing you when mounting them. If using a three piece clamp, then make sure space between each clamp segment is equally spaced. Image 7: Die Clamp Corresponding Letters
Each die clamp that Jacobs Corporation sells is equipped with three bolts and set of washers. The following are key points to consider when inserting clamp bolts: Each bolt has a set of washers, two convex and two concave. Proper positioning of these washers is required. You should ways allow for the flat surfaces of the washers to be touching the bolt head, nut, and clamp surface. Images below illustrate positioning of washers. Image 8: Die Clamp Bolts Washer Positioning Image 9: Die Clamp Bolts Washer Positioning
Wear Stage on Die Clamp As mentioned before, incorporating a schedule to periodically check wear stage on your die clamps is essential for a continues operating process. Once die clamps are past second stage wear they need to be replaced, otherwise they will not provide support to your dies and possible die breakage may occur. The cost of replacing die clamps is nothing when compared to the cost of replacing dies and downtime. Image 10: Die Clamp Wear Stage Image 11: Die Clamp Wear End Section Image 12: Die Clamp Wear Middle Section
The following four steps are for gauging your die clamps. Step 1: Fit Gauge squarely across clamp on NO.1 side. If Gauge bottoms out on then clamp is in 1 st Stage Wear. Clamp is usable. Proceed to Step 2 to check for further wear. Step 2: Move Gauge left & right, if there is any side clearance then clamp is past 1 st Stage Wear. Clamp is usable. Proceed to Step 3 to check for further wear. Step 3: Fit Gauge squarely across clamp on NO.2 side. If Gauge bottoms out on then clamp is in 2 nd Stage Wear and should not be used and need to be replaced soon. Proceed to Step 4 to check for further wear. Step 4: Move Gauge left & right, if there is any side clearance then clamps are past 2 nd Stage Wear. The clamps are ETREMELY worn and require IMMEDIATE replacement! Image 13: Die Clamp Gauge - Instructions
Wear Stage on Pellet Mill Quill Every time you replace a die it is important that you verify stage wear on your pellet mill quill. Replacement is required when the quill is past second stage wear. Any loose fitment between your die and quill is a possible cause of die fractures. Please contact your pellet mill manufacturer to discuss wear and to order a replacement. The following images illustrate sections to check for wear. Image 14: Pellet Mill Quill Image 15: Pellet Mill Quill Stage Wear Image 16: Pellet Mill Quill Sections to Check
Four steps for gauging your pellet mill quill. Step 1: Fit Gauge squarely across Quill on NO.1 side. If Gauge bottoms out on then Quill is in 1 st Stage Wear. Quill is usable. Proceed to Step 2 to check for further wear. Step 2: Move Gauge left & right, if there is any side clearance then Quill is past 1 st Stage Wear. Quill is usable. Proceed to Step 3 to check for further wear. Side Clearance Step 3: Fit Gauge squarely across Quill on NO.2 side. If Gauge bottoms out on then Quill is in 2 nd Stage Wear. Quill needs to be replaced. Continue to Step 4 to check for further wear. Step 4: Move Gauge left & right, if there is any side clearance then Quill is past 2 nd Stage Wear. Quill is ETREMELY worn and requires IMMEDIATE replacement! Image 17: Pellet Mill Quill - Instructions
Roller Adjustment Accurate roller adjustment is essential to prolong the life of the die and shells. Tight roll shell contact can induce die pad damages and accelerate the wear process on the die. Creating pressure on the die will introduce stress on the material leading to possible breakage. On the other hand if your roll shell adjustment is loose it can reduce pelleting capacity and create plugging. Standard dies and Lightning dies should be adjusted differently, for example, most standard dies are run on a skiptouch method while for the Lightning dies less pressure is required which means a small distance between the die pad and shells should exist. The created distance provides the benefit of expanding the life of your die and shells as less metal-to-metal contact is seen. When operating your die on low speed (RPM) having a skip-touch method is recommended to experience less friction. It is recommended that for every new die you start with new shells for best performance. Image 18: Roll Shell Placement
Below are possible results from improper roll shell placement. Image 19: New Die Pad Image 20: Uneven Wear Pad Image 21: Die Peening Image 22: Die Rolled Over
Tramp Metal Periodic inspection of the die for presence of tramp metal is recommended. Tramp metal can become embedded in the die and should be removed by punching or drilling from the outside of the die (die face). Magnets, scalpers, and other cleaning devices are essential to prolong the life of the die. Maintenance schedule to clean magnets should be implemented to ensure they are working properly and less metal is reaching the dies. Wear Parts Image 23: Tramp Metal Keeping track of a replacement schedule for your mill wear parts is recommended to prevent die movement and fractures. The leading reason for die movement is due to worn die clamps and wear rings. Die clamps provide support for the die while in operation. A clamp gauge needs to be utilized when checking wear stage on your clamps. When clamps are at first stage wear, close monitoring is advised. If past second stage wear, they must be replaced. Image 24, shown below, illustrates a polished surface which means the die was exposed to movement. Inadequate support will induce excessive stress on the material leading to possible fractures. Image 24: Polished Surface-Clamp Area
Wear rings provide support while die is operating. It is recommended to replace them at least every third die as there is not a clear indication of wear stage. The replacement period will also depend on total tonnage on the die and it is recommended not to exceed more than a year. Worn out wear rings will not provide support to die and movement may be generated. Again, the polished surface suggests inadequate support. Image 25: Polished Surface-Wear Ring Area The key way is for location purposes and any deformation to this area can lead to movement. Periodic inspection is recommended to check for abnormalities. Image 26: Damaged Key Way
Pellet mill manufacturing companies have recommendations on what grade bolt and size should be utilized for operating dies. It is important to use recommended bolts to be within desired mechanical properties, yield and tensile strength. Metric Grade Bolt SAE Grade Bolt 5.8 2 8.8 5 10.9 8 Table 1: Metric vs SAE Grade Bolt Having a scheduled preventive maintenance will allow the operator to become aware of any abnormalities and prevent damages. Below is a recommended schedule you can follow for your pellet mill. Preventive Maintenance Daily Die Replacemnt Inspect die Die pad Bolts Tramp metal Clean off magnets Inspect shell condition Lubrication Inspect grease system Lubricate rollers if manually Every 4 hours Pellet Mill Check quill wear with gauges Check die clamps with gauges if past second stage wear then replacement is needed Replacement of wear ring Table 2: Preventive Maintenance Schedule Jose Martinez; Sales Engineer Work: 712-755-3131 Ext 254 Cell: 712-579-4686 jmartinez@jacobscorp.com Jacobs Corporation