This ball mill and rod mill power draw model is based on a torque model and empirical measurements made by the Nordberg Equipment Company for use by its sales representatives to size grinding mills. Slight differences in the equations used allow rod mills, dry ball mills and wet overflow and grate ball mills to be sized.
This model was published by the Nordberg equipment company with versions of it appearing in their "Red Book" equipment sizing manual in the 1970's. The latest version of this model published was by the Outokumpu company (now Outotec) publication "The Science of Comminution" (undated, but probably about 2002).
The model output is the "US horsepower per foot of mill length" where the power is measured at the mill shell. Multiplying this output by the mill effective grinding length and converting the result to modern units of power results in the mill power draw at the shell in kilowatts.
Each of the three original inputs are fit to equations based on the Nordberg published tables that generate, respectively, values for Factor A, Factor B and Factor C which are multiplied together. There are slightly different versions of the Factor B for different styles of mills. The equation presented below is for wet overflow ball mills.
The Outokumpu reference gives the base mill charge density for these formulae as 310 lb/ft3. This translates to a charge density of 5050 kg/m3. Knowing the actual density of the charge allows the correction to be calculated as:
The effective grinding length of a rod mill is the belly length of the mill inside the mill liners from the inside of the head end liner to the inside of the discharge end liner or grate. The length of the rods is expected to be six inches less than the EGL.
Mill manufacturers often describe a different length, the cylinder length or the flange-to-flange length. This flange-to-flange length is usually six inches more than the EGL for overflow mills. The flange-to-flange length may be anywhere between 1.5 and 3 feet longer than the EGL for grate mills (more throughput usually requires deeper discharge chambers behind the grate).
Food mills have been around for many years, making the process of cooking a lot easier. Thanks to advancements in technology, changes have been made to the cooking mills, but manufacturers build both manual and electricity-powered models.
The best food mill for you will largely depend on your needs. Since the market is flooded with so many options, choosing one is a task, so its a good idea to exercise a guided decision. This article lists some of the best food mills on the market, and all you need to know about them while youre on the hunt for one.
Eliminate some of the hassle of processing your vegetables, potatoes, tomatoes manually using the Oxo Good Grip Food Mill. Sure, an electric blender is one way to go, but with a food mill, you can achieve a more delicate blend since it eliminates the tiny seeds in the sauce.
This impressive kitchenware is effective, but its also quite safe as the inner bowl is durable stainless steel, and say goodbye to rust, which contaminates or stains the food. Thats not all; the machine comes with three grinding discs to deliver different textures depending on your preferences. Even better, the manufacturer also added a secure disc exchange mechanism to make your food processing a breeze. Furthermore, this model comes with versatile foldable, slip-proof legs that secure the food mill over a container or pot. The foldable leg design also makes it easy to store once you when food preparation is complete.
Whether its the food mill itself or the blade, the handle is designed to give a comfortable, non-slip grip and an easy to use experience. Youll also love that its easy to clean, you can either throw it in the dishwasher or wash it by hand. Altogether, youll find this versatile piece of equipment to be a useful addition to your kitchen arsenal.
This device comes in with all the little extra bits to deliver comfortable and practical use. Cuisipro Deluxe Food Mill features an extra-large stainless steel bowl for making a large amount of sauce. If you are a hotel chef or a super mom who makes unique recipes in large quantities, this is a must-have.
The rotating crank has a firm-grip knob at the end so that the milling process can be low effort. Also, the Cuisipro Deluxe is furnished with a special scraper to evacuate pure into the container or pot placed under the mill.
The device is entirely dishwasher-friendly, and what makes its easy to take apart. If you want to clean by hand, then thats fine too, as the steel material allows easy removal of masticated food without any stains or residue.
From top to bottom, including the three interchangeable milling disc, the Weston 61-0101-W Food Mill is finished with a durable steel design and a large capacity of almost 2 quarts to accommodate more of the food you want to process. If you need to make tomato sauce, just launch the 2 mm grinding disc, and you are guaranteed a smooth sauce with practically no seeds.
Also, theres a 3mm and 8mm disc for tailor-fit milling. Once you load your vegetables, turn the crank in one direction to mill and the other direction when you are ready to discharge the food. Additionally, maintenance is equally easy.
If you have a dishwasher, the stainless steel material is dishwasher safe, and you can opt to clean it by hand easily. You shouldnt have any problem assembling it; however, one must pay close attention during blade installation. For some more must-have kitchen products, check out our list of the best graters on the market.
If you are on a budget and you are looking out for a food mill thatll do what you want it to do, then the Granite Ware Stainless Steel Deluxe Food Mill is a great choice. Its ideal for the preparation of the most delicate pure, sauces, and soup. Get one of these, and youll find that seeding and peeling will become a walk in the park, just like with an immersion blender.
If you want to use this to make jam, itll get almost all the seeds out, if not all, and you can use it to prepare baby food. The versatile food mill comes with three discs for the preparation of meals of different textures. So, whether you want to make a smooth jam, medium-textured apple sauce, or much chunky mashed potatoes, you are covered. Furthermore, the all stainless steel food mill employs a very lightweight design, so youll find it easy to carry it if you need to. In terms of maintenance, either hand wash it or throw it in the dishwasher.
It may also interest you to know Graniteware has been in the kitchenware business since 1901. Since then, theyve had the opportunity to develop the materials used and it shows in the stainless steel with carbon finishing for added strength and rust resistance. For less than $30, this 2-quart food mill is almost a steal.
Rsle Stainless Steel Food Mill Is a beautifully finished piece of kitchenware, and you cant ignore the exquisite finish. Like many food mills, Rsle made this one manual with an ergonomic knob for a comfortable, slip-proof grip as you rotate the blade. The food mills design ensures it doesnt fall short in terms of effectiveness or efficiency. Youll also notice theres almost no space between the blade and sieve below. This configuration is to ensure that peeling, seeding, and the overall milling processes are effortless with each rotation.
Unlike some other food mills, you wont have to keep supporting this device with your hands to get enough blade pressure. This food mill comes with two interchangeable milling discs for processing foods at different textures. Some food mills come with three discs. Rsle food mills included discs deliver finer-textured food. As such, its 0.04 and 0.1-inch grinding disc can effectively process jams, baby food, and similar.
Thats not all, for easy usage when milling, the food mill comes with 3 downward curved support hooks to secure it on a bowl or pot. Sure, it comes in a little pricey but youll be glad you made the right decision. A lifetime warranty also comes with your purchase. But you wont need it because you can never go wrong with German-made equipment, youll always find them in grandmas cabinet many years later still working like new. If you want to try something new in the kitchen, check out these amazing sous videsyou might like.
This impressive unit combines full stainless steel material, electric mill grinder, and a power-saving motor to deliver a high-efficiency grain crusher. The ALDKitchen ALD-S3000 Grain Mill Grinder has a high capacity of 3000g, adequate for people who want to use it as a commercial miller in a hotel, shop, etc. So, go ahead and engage the ALF-S3000 to process all types of grain, and youll notice how incredibly easy it is to use.
In addition to the high capacity, the speed of operation is equally commendable as this miller saves time when you need to process a large amount of grain, turning it into smooth powder in no time. The ALD-S3000 can process grains such as soya bean, dried corn, peanut, and also root spices such as ginger, etc.
The mill includes a buckle that eliminates the possibility of waste despite the high speed of grinding. Simply pour your grain in and turn the analog control. To ensure the mill doesnt burnout in a short time, the manufacturer furnishes the electric motor with a device that protects the machine from overload. Even better, you dont have to have to go through the process of lifting the entire mill to pour out your processed grain. You can simply lift the upper section to get the powder out. Its a little pricey, but you wont regret each dollar spent on this cool kitchen gadget.
From berry processing to baby food preparation, the RSVP International Endurance Food Mill got you covered. Designed and finished with durable stainless steel material, your milling operation is guaranteed to be a breeze and non-reactive with the food. The package comes with three different interchangeable grinding discs made with durable steel.
This mill is a manually operated unit, so ergonomics is essential. The manufacturer understands, so they furnish the mill with a long handle for leverage. The handle itself is a combination of steel and wood finishing, so for best results, the maintenance is best done by hand. The dishwasher may not be ideal for cleaning this device due to the wood components. However, the three versatile, stainless steel discs are dishwasher safe. Our buying guide on the best woks features some more quality kitchen products you might like.
Uniquely designed to process foods in both fine and medium textures, Gefu Stainless Steel Food Mill FLOTTE LOTTE comes in with stainless steel disks equipped with 2.0mm and 3.0mm perforations. This mill is not the choice for coarser preparations. A 2-quart capacity allows a moderate food processing volume. One of the best things about the Gefu FLOTTE LOTTE is the ease of use. You will be surprised at how incredibly painless your sauce making journey will be. The blades position and configuration process foods quickly, and youll be applying little effort.
Even better, the food mill is compact, making it easy to fit into the dishwasher and store. Youll have no worries about this sturdy food mill at all; Gefu builds it to last. If you need a product suitable for meat, here is our list of the top meat grinders that will do the trick.
For less than $50, this is another food mill that delivers excellent sauce making without pain and discomfort. The Mirro 50024 Foley Stainless Steel Food Mill comes with a capacity of 2-quart and steel material construction for efficient food milling. With this material, theres no chipping, no staining or discoloration of any kind, so its okay if you want to use this to mix your babys food.
Altogether, its a versatile tool that can mash, grate, and process your food to the desired texture, and even replace your smoothie blender. If you are a chef, youve got to have this companion in your kitchen. Whats more, you dont have to worry about wasting energy. This food mill is efficiently designed with a rotating crank and an ergonomic knob to make milling simple and effective.
Furthermore, the mill weighs less than two pounds altogether so you can swing it anywhere easily. The manufacturer also furnished the mill with a bowl or pot-secure support for non-slip user experience. Its equally easy to assemble and equally easy to clean, either by machine or hand. A couple of users complained the mill left their food with some metallic/black residue. So, you may need to correctly piece it together to avoid high friction movement and a similar experience.
Materials - This is an area you cannot afford to compromise on for any reason. The materials used in the construction of your food mill must first be safe, then durable. In terms of safety, because there's a lot of friction involved in the movement of the bowl, you cannot afford to have a material that will easily chip, cause discoloration, or leave an unpleasant smell behind, especially when the food is hot. Therefore, the best material with the lowest probability of creating any of the above is stainless steel. While the quality of stainless steel also differs, it is still one of the best materials to use compared to plastic or any other coated metal.
Capacity - This is how large the mill bowl is, both in depth and in diameter. While this may not directly affect the effectiveness of your food mill, efficiency might be compromised. A deep-mouthed food mill may come in handy when you want to whip up a large amount of pure. Instead of milling in batches, you'll easily swing it at a go. In addition, a food mill that's significantly too small can make food spin out of the bowl while processing. So, look out for at least a 2-quart capacity or more.
Table-Mounted vs. Rotary Food mills that operate manually are either rotary or mounted on tables. The rotary style works in a container that houses the processed food - either a bowl or pot. This configuration is ideal for 1- 5 quarts of food and frequently mounted on the table with the aid of a clamp. They often have a capacity of over a gallon and operate quickly. Operating them is faster and eliminates the awkwardness of holding the mill while you also rotate the crank. If your food mill is for occasional home use, you can easily opt for the rotary type. However, if you run a small or large commercial operation, like a hotel kitchen or restaurant, a mounted food mill may be ideal.
Electric v. Manual - If you've got a food mill at home, it's likely you have the manual type with rotating handles because they are a lot more common. Again, this is ideal for processing foods that are not very large in quantity or don't require urgency. Electric food mills are, of course, powered by electricity s the milling operation is effortless and faster. They also come in larger sizes and are usually quite expensive. If you can afford it, it can become handy when you need to process large volumes of food. But remember, if you need to prepare food in an electricity-devoid location, the manual food mill can be a lifesaver.
Blades - Blades are an essential part of the food mill. Like the bowl, they must be stainless steel and sharp. But these are not enough for a food mill to be capable. If the edge is too angled, and there is too much distance to the grinding disc, your food will swirl around instead of being forced through the sieve.
Discs - The sieve disc or grinding disc determines the texture of the processed food. Most food mills come with interchangeable discs so that you can change as you desire i.e., fine, medium, or coarse texture. Some may come with only two discs, so make sure the hole size of the available disc is something you can work with otherwise opt for a design with more disc options.
Handles, Cranks, and Hooks - The handle, crank, and hook of a food mill can make you make your milling experience fantastic or a struggle. Make sure you opt for a design with an ergonomic handle that delivers a comfortable, slip-proof grip. Also, the crank used in rotating the blade should have a good grip. So, look out for those with ergonomic knob designs. Furthermore, hooks are features that give balance to rotary food mills placed on a bowl or pot. The hooks ensure the mill doesn't slip off and makes work efficient.
A: A rotating blade grabs and crushes the food. The spinning forces the food through the holes of the disc into a bowl or pot placed below. This process also separates the seeds of fruits such as berry etc.
A: Food mills process food by crushing and extracting the skins and seed if any is present while the food processor minces food and pures both the seed and skin along with the food. This process may impact the taste or look and may require some effort to pick them out by hand.
A: Milling means to grind or change the texture and separate components of food not needed from the ones required. It either completes the cooking process, e.g., crushing cooked hot potatoes or precedes the actual cooking like it's done when making a tomato sauce. Altogether, it makes cooking easier and food softer to eat.
Am sure your BallMill is considered the finest possible grinding mill available. As such you will find it is designed and constructed according to heavy duty specifications. It is designed along sound engineering principles with quality workmanship and materials used in the construction of the component parts. YourBallMill reflects years of advancement in grinding principles, materials, and manufacturing techniques. It has been designed with both the operators and the erectors viewpoints in mind. Long uninterrupted performance can be expected from it if the instructions covering installation and maintenance of the mill are carried out. You may be familiar with installing mills of other designs and manufacture much lighter in construction. YourBallis heavy and rugged. It should, therefore, be treated accordingly with due respect for its heavier construction.
The purpose of this manual is to assist you in the proper installation and to acquaint you a bit further with the assembly and care of this equipment. We suggest that these instructions be read carefully and reviewed by everyone whenever involved in the actual installation and operation of the mill. In reading these general instructions, you may at times feel that they cover items which are elementary and perhaps not worthy of mention; however in studying hundreds of installations, it has been found that very often minor points are overlooked due to pressure being exerted by outside influences to get the job done in a hurry. The erection phase of this mill is actually no place to attempt cost savings by taking short cuts, or by-passing some of the work. A good installation will pay dividends for many years to come by reduced maintenance cost.With the modern practice of specialized skills and trades, there is often a line drawn between responsibilities of one crew of erectors and another. Actually the responsibility of installation does not cease with the completion of one phase nor does it begin with the starting of another. Perhaps a simple rule to adopt would be DO NOT TAKE ANYTHING FOR GRANTED. This policy of rechecking previously done work will help guarantee each step of the erection and it will carefully coordinate and tie it into subsequent erection work. To clarify or illustrate this point, take the example of concrete workers completing their job and turning it over to the machinist or millwright. The latter group should carefully check the foundation for soundness and correctness prior to starting their work.
Sound planning and good judgement will, to a great extent, be instrumental in avoiding many of the troublesome occurrences especially at the beginning of operations. While it is virtually impossible to anticipate every eventuality, nevertheless it is the intention of this manual to outline a general procedure to follow in erecting the mill, and at the same time, point out some of the pitfalls which should be avoided.
Before starting the erection of the mill, adequate handling facilities should be provided or made available, bearing in mind the weights and proportions of the various parts and sub-assemblies. This information can be ascertained from the drawings and shipping papers.
The gearing, bearings, and other machined surfaces have been coated with a protective compound, and should be cleaned thoroughly with a solvent, such as Chlorothene, (made by Dow Chemical). Judgement should be exercised as to the correct time and place for cleaning the various parts. Do not permit solvents, oil or grease to come in contact with the roughened top surfaces of the concrete foundation where grouting is to be applied; otherwise proper bonding will not result.
After cleaning the various parts, the gear and pinion teeth, trunnion journals and bearings, shafting and such, should be protected against rusting or pitting as well as against damage from falling objects or weld splatter. All burrs should be carefully removed by filing or honing.
Unless otherwise arranged for, the mill has been completely assembled in our shop. Before dismantling, the closely fitted parts were match marked, and it will greatly facilitate field assembly to adhere to these match marks.
The surfaces of all connecting joints or fits, such as shell and head flanges, trunnion flanges, trunnion liner and feeder connecting joints, should be coated with a NON-SETTING elastic compound, such as Quigley O-Seal, or Permatex to insure against leakage and to assist in drawing them up tight. DO NOT USE WHITE LEAD OR GREASE.
Parts which are affected by the hand of the mill are easily identified by referring to the parts list. In general they include the feeder, feed trunnion liner, discharge trunnion liner if it is equipped with a spiral, spiral type helical splitter, and in some cases the pan liners when they are of the spiral type. When both right and left hand mills are being assembled, it is imperative that these parts which involve hand be assembled in the correct mill.
Adequate foundations for any heavy equipment, and in particular grinding mills, are extremely important to assure proper operation. The foundation should preferably be in one piece, that is, with a reinforced slab footing (so called mat) extending under both trunnion bearing foundations as well as the pinion bearing foundation. If possible or practical, it should be extended to include also the motor and drive. With this design, in the event of some movement, the mill and foundation will tend to move as a unit. ANY SLIGHT SETTLING OF FOUNDATIONS WILL CAUSE BEARING AND GEAR MISALIGNMENT, resulting in excessive wear and higher maintenance costs. It has been found that concrete foundations on a weight basis should be at least 1 times the total weight of the grinding mill with its grinding media.
Allowable bearing pressure between concrete footings and the soil upon which the foundation rests should first be considered. The center of pressure must always pass through the center of the footing. Foundations subject to shock should be designed with less unit pressure than foundations for stationary loads. High moisture content in soils reduces the amount of allowable specific pressure that the ground can support. The following figures may be used for preliminary foundation calculations.
Portland cement mixed with sand and aggregate in the proper proportions has come to be standard practice in making concrete. For general reference cement is usually shipped in sacks containing one cubic foot of material. A barrel usually holds 4 cubic feet. Cement will deteriorate with age and will quickly absorb moisture so it should be stored in a dry place. For best results the sand and gravel used should be carefully cleaned free of humus, clay, vegetal matter, etc.
Concrete may be made up in different mixtures having different proportions of sand and aggregate. These are expressed in parts for example a 1:2:4 mixture indicates one bag of cement, 2 cubic feet of sand, and 4 cubic feet of gravel. We recommend a mixture of 1:2:3 for ball mill and rod mill foundations. The proper water to sand ratio should be carefully regulated since excess water increases the shrinkage in the concrete and lends to weaken it even more than a corresponding increase in the aggregate. Between 5 to 8 gallons of water to a sack of cement is usually recommended, the lower amount to be used where higher strength is required or where the concrete will be subject to severe weathering conditions.
Detailed dimensions for the concrete foundation are covered by the foundation plan drawing submitted separately. The drawing also carries special instructions as to the allowance for grouting, steel reinforcements, pier batter, foundation bolts and pipes. During concrete work, care should be taken to prevent concrete entering the pipes, surrounding the foundations bolts, which would limit the positioning of the bolts when erecting the various assemblies. Forms should be adequately constructed and reinforced to prevent swell, particularly where clearance is critical such as at the drive end where the gear should clear the trunnion bearing and pinion bearing piers.
For convenience in maintenance, the mill foundations should be equipped with jacking piers. These will allow the lifting of one end of the mill by use of jacks in the event maintenance must be carried out under these conditions.
Adequate foundations for any heavy equipment, and in particular Marcy grinding mills, are extremely important to assure proper operation of that equipment. Any slight settling of foundations will cause bearing and gear misalignment, resulting in excessive wear and higher maintenance costs. It has been found that concrete foundations on a weight basis should be approximately 1 times the total weight of the grinding mill with its grinding media.
Allowable bearing pressure between concrete footings and the soil upon which the foundation rests should first be considered. The center of pressure must always pass through the center of the footing. Foundations subject to shock should be designed with less unit pressures than foundations for stationary loads. High moisture content in soils reduces the amount of allowable pressure that that material can support. The following figures may be used for quick foundation calculations:
Portland cement mixed with sand and aggregate in the proper proportions has come to be standard practice in making concrete. For general reference cement is usually shipped in sacks containing one cubic foot of material. A barrel usually consists of 4 cubic feet. Cement will deteriorate with age and will quickly absorb moisture so it should be stored in a cool, dry place. The sand and gravel used should be carefully cleaned for best results to be sure of minimizing the amount of sedimentation in that material.
Concrete may be made up in different mixtures having different proportions of sand and aggregate. These are expressed in parts for example a 1:2:4 mixture indicates one bag of cement, 2 cubic feet of sand, and 4 cubic feet of gravel. We recommend a mixture of 1:2:3 for ball mill and rod mill foundations. The proper water to sand ratio should be carefully regulated since excess water will tend to weaken the concrete even more than corresponding variations in other material ratios. Between 5 to 8 gallons of water to a sack of cement is usually recommended, the lower amount to be used where higher strength is required or where the concrete will be subject to severe weathering conditions.
We recommend the use of a non-shrinking grout, and preferably of the pre-mixed type, such as Embeco, made by the Master Builders Company of Cleveland, Ohio. Thoroughly clean the top surfaces of the concrete piers, and comply with the instructions of the grouting supplier.
1. Establish vertical and horizontal centerline of mill and pinion shaftagainst the effects of this, we recommend that the trunnion bearing sole plate be crowned so as to be higher at the center line of the mill. This is done by using a higher shim at the center than at the endsand tightening the foundation bolts of both ends.
After all shimming is completed, the sole plate and bases should be grouted in position. Grouting should be well tamped and should completely fill the underside of the sole plate and bases. DO NOT REMOVE THE SHIMS AFTER OR DURING GROUTING. When the grout has hardened sufficiently it is advisable to paint the top surfaces of the concrete so as to protect it against disintegration due to the absorption of oil or grease.
If it is felt that sufficient accuracy in level between trunnion bearing piers cannot be maintained, we recommend that the grouting of the sole plate under the trunnion bearing opposite the gear end be delayed until after the mill is in place. In this way, the adjustment by shimming at this end can be made later to correct for any errors in elevation. Depending on local climatic conditions, two to seven days should he allowed for the grouting to dry and set, before painting or applying further loads to the piers.
Pinion bearings are provided of either the sleeve type or anti-friction type. Twin bearing construction may use either individual sole plates or a cast common sole plate. The unit with a common sole plate is completely assembled in our shop and is ready for installation. Normal inspection and cleaning procedure should be followed. Refer to the parts list for general assembly. These units are to be permanently grouted in position and, therefore, care should be taken to assure correct alignment.
The trunnion bearing assemblies can now be mounted on their sole plates. If the bearings are of the swivel type, a heavy industrial water-proof grease should be applied to the spherical surfaces of both the swivels and the bases. Move the trunnion bearings to their approximate position by adjustment of the set screws provided for this purpose.
In the case of ball mills, all internal wearing parts will pass through the manhole, whereas in the case of open end rod mills they will pass through the discharge trunnion opening. When lining the shell, start with the odd shaped pieces around the manhole opening if manholes are furnished. Rubber shell liner backing should be used with all cast type rod mills shell liners. If the shell liners are of the step type, they should be assembled with the thin portion, or toe, as the leading edge with respect to rotation of the mill.
Lorain liners for the shell are provided with special round head bolts, with a waterproof washer and nut. All other cast type liners for the head and shell are provided with oval head bolts with a cut washer and nuts. Except when water proof washers are used, it is advisable to wrap four or five turns of candle wicking around the shank of the bolt under the cut washer. Dip the candle wicking in white lead. All liner bolt threads should be dipped in graphite and oil before assembly. All liner bolt cuts should be firmly tightened by use of a pipe extension on a wrench, or better yet, by use of a torque wrench. The bolt heads should be driven firmly into the bolt holes with a hammer.
In order to minimise the effect of pulp race, we recommend that the spaces between the ends of the shell liners and the head liners or grates be filled with suitable packing. This packing may be in the form of rubber belting, hose, rope or wood.
If adequate overhead crane facilities are available, the heads can be assembled to the shell with the flange connecting bolts drawn tightly. Furthermore, the liners can be in place, as stated above, and the gear can be mounted, as covered by separate instructions. Then the mill can be taken to its location and set in place in the trunnion bearings.
If on the other hand the handling facilities are limited it is recommended that the bare shell and heads be assembled together in a slightly higher position than normal. After the flange bolts are tightened, the mill proper should be lowered into position. Other intermediate methods may be used, depending on local conditions.
In any event, just prior to the lowering of the mill into the bearings the trunnion journal and bushing and bases should be thoroughly cleaned and greased. Care should be taken not to foul the teeth in the gear or pinion. Trunnion bearing caps should be immediately installed, although not necessarily tightened, to prevent dirt settling on the trunnions. The gear should be at least tentatively covered for protection.
IMPORTANT. Unless the millwright or operator is familiar with this type of seal, there is a tendency to assume that the oil seal is too long because of its appearance when held firmly around the trunnion. It is not the function of the brass oil seal band to provide tension for effective sealing. This is accomplished by the garter spring which is provided with the oil seal.
Assemble the oil seal with the spring in place, and with the split at the top. Encircle the oil seal with the band, keeping the blocks on the side of the bearing at or near the horizontal center line so that when in place they will fit between the two dowel pins on the bearing, which are used to prevent rotation of the seal.
Moderately tighten up the cap screws at the blocks, pulling them together to thus hold the seal with its spring in place. If the blocks cannot be pulled snuggly together, then the oil seal may be cut accordingly. Oil the trunnion surface and slide the entire seal assembly back into place against the shoulder of the bearing and finish tightening. Install the retainer ring and splash ring as shown.
In most cases the trunnion liners are already mounted in the trunnions of the mills. If not, they should be assembled with attention being given to match marks or in some cases to dowel pins which are used to locate the trunnion liners in their proper relation to other parts.
If a scoop feeder, combination drum scoop feeder or drum feeder is supplied with the mill, it should be mounted on the extended flange of the feed trunnion liner, matching the dowel pin with its respective hole. The dowel pin arrangement is provided only where there is a spiral in the feed trunnion liner. This matching is important as it fixes the relationship between the discharge from the scoop and the internal spiral of the trunnion liner. Tighten the bolts attaching the feeder to the trunnion liner evenly, all around the circle, seating the feeder tightly and squarely on its bevelled seat. Check the bolts holding the lips and other bolts that may require tightening. The beveled seat design is used primarily where a feeder is provided for the trunnion to trunnion liner connection, and the trunnion liner to feeder connection. When a feeder is not used these connecting joints are usually provided by a simple cylindrical or male and female joint.
If a spout feeder is to be used, it is generally supplied by the user, and should be mounted independently of the mill. The spout should project inside the feed trunnion liner, but must not touch the liner or spiral.
Ordinarily the feed box for a scoop tender is designed and supplied by the user. The feed box should be so constructed that it has at least 6 clearance on both sides and at the bottom of the scoop. This clearance is measured from the outside of the feed scoop.
The feed box may be constructed of 2 wood, but more often is made of 3/16 or plate steel reinforced with angles. In the larger size mills, the lower portion is sometimes made of concrete. Necessary openings should be provided for the original feed and the sand returns from the classifiers when in closed circuit.
A plate steel gear guard is furnished with the mill for safety in operation and to protect the gear and pinion from dirt or grit. As soon as the gear and pinion have been cleaned and coated with the proper lubricant, the gear guard should be assembled and set on its foundation.
Most Rod Mills are provided with a discharge housing mechanism mounted independently of the mill. This unit consists of the housing proper, plug door, plug shaft, arm, and various hinge pins and pivot and lock pins. The door mechanism is extra heavy throughout and is subject to adjustment as regard location. Place the housing proper on the foundation, level with steel shims and tighten the foundation bolts. The various parts may now be assembled to the housing proper and the door plug can be swung into place, securing it with the necessary lock pins.
After the mill has been completely assembled and aligned, the door mechanism centered and adjusted, and all clearances checked, the housing base can be grouted. The unit should be so located both vertically and horizontally so as to provide a uniform annular opening between the discharge plug door and the head liners.
In some cases because of space limitation, economy reasons, etc., the mill is not equipped with separate discharge housing. In such a case, the open end low discharge principal is accomplished by means of the same size opening through the discharge trunnion but with the plug door attached to lugs on the head liner segments or lugs on the discharge trunnion liner proper. In still other cases, it is sometimes effected by means of an arm holding the plug and mounted on a cross member which is attached to the bell of the discharge trunnion liner. In such cases as those, a light weight sheet steel discharge housing is supplied by the user to accommodate the local plant layout in conjunction with the discharge launder.
TRUNNION BEARING LUBRICATION. For the larger mills with trunnion bearings provided with oil seals, we recommend flood oil lubrication. This can be accomplished by a centralized system for two or more mills, or by an individual system for each mill. We recommend the individual system for each mill, except where six or more mills are involved, or when economy reasons may dictate otherwise.
In any event oil flow to each trunnion bearing should be between 3 to 5 gallons per minute. The oil should be adequately filtered and heaters may be used to maintain a temperature which will provide proper filtration and maintain the necessary viscosity for adequate flow. The lines leading from the filter to the bearing should be of copper tubing or pickled piping. The drain line leading from the bearings to the storage or sump tank should be of adequate size for proper flow, and they should be set at a minimum slope of per foot, perferably per foot. Avoid unnecessary elbows and fittings wherever possible. Avoid bends which create traps and which might accumulate impurities. All lines should be thoroughly cleaned and flushed with a solvent, and then blown free with air, before oil is added.
It is advisable to interlock the oil pump motor with the mill motor in such a way that the mill cannot be started until after the oil pump is operating. We recommend the use of a non-adjuslable valve at each bearing to prevent tampering.
When using the drip oil system it is advisable to place wool yarn or waste inside a canvas porous bag to prevent small pieces of the wool being drawn down into the trunnion journal. If brick grease is used, care should be taken in its selection with regard to the range of its effective temperature. In other words, it should be pointed out that brick grease is generally designed for a specific temperature range. Where the bearing temperature does not come up to the minimum temperature rating of the brick grease, the oil will not flow from it, and on the other hand if the temperature of the bearing exceeds the maximum temperature rating of the brick grease, the brick is subject to glazing; therefore, blinding off of the oil. This brick should be trimmed so that it rests freely on the trunnion journal, and does not hang up, or bind on the sides of the grease box.
When replacing the brick grease, remove the old grease completely. Due to the extended running time of brick grease, there is usually an accumulation of impurities and foreign matter on the top surface, which is detrimental to the bearing.
Where anti-friction bearings are supplied, they are adequately sealed for either grease or oil lubrication. If a flood system is used for the trunnion bearings and it is adequately filtered, it can then be used for pinion bearings with the same precautions taken as mentioned above, with a flow of to 1 gallons per minute to each bearing.
These lubricants can be applied by hand, but we highly recommend some type of spray system, whether it be automatic, semi-automatic or manually operated. It has been found that it is best to lubricate gears frequently with small quantities.
Start the lubrication system and run it for about ten minutes, adjusting the oil flow at each bearing. Check all of the bolts and nuts on the mill for tightness and remove all ladders, tools and other obstructions prior to starting the mill.
Before starting the mill, even though it is empty, we recommend that it be jogged one or two revolutions for a check as to clearance of the gear and its guard, splash rings, etc. The trunnion journal should also be checked for uniform oil film and for any evidence of foreign material which might manifest itself through the appearance of scratches on the journal. If there are any scratches, it is very possible that some foreign material such as weld splatter may have been drawn down into the bushing, and can be found imbedded there. These particles should be removed before proceeding further.
If everything is found to be satisfactory, then the mill should be run for ten to fifteen minutes, and stopped. The trunnion bearings should be checked for any undue temperature and the gear grease pattern can be observed for uniformity which would indicate correct alignment.
It should be noted that with an empty mill the reactions and operating characteristics of the bearings and gearing at this point are somewhat different than when operating with a ball or rod charge. Gear noises will be prominent and some vibration will occur due to no load and normal back-lash. Furthermore, it will be found that the mill will continue to rotate for some time after the power is shut off. Safety precautions should therefore he observed, and no work should be done on the mill until it has come to a complete stop.
We have now reached the point where a half ball or rod charge can be added, and the mill run for another six to eight hours, feeding approximately half the anticipated tonnage. The mill should now be stopped, end the gear grease pattern checked, and gear and pinion mesh corrected, if necessary, according to separate instructions.
The full charge of balls or rods can now be added, as well as the full amount of feed, and after a run of about four to six days, ALL BOLTS SHOULD AGAIN BE RETIGHTENED, and the gear and pinion checked again, and adjusted if necessary.
Where starting jacks are provided for the trunnion bearings of the larger sized mills, they should be filled with the same oil that is used for the lubrication of the trunnion bearings. Before starting the mill they should be pumped so as to insure having an oil film between the journal and the bushing.
When relining any part of the mill, clean away all sand from the parts to be relined before putting in the new liners. For the head liners and shell liners you may then proceed in the same manner used at the time of the initial assembly.
Before relining the grate type discharge head, it is advisable to refer to the assembly drawings and the parts list.Because of such limitations as the size of the manhole opening, and for various other reasons, it will be found that the center discharge liner and cone designs vary. The cone may be a separate piece or integral with either the trunnion liner, or the router discharge liner. Furthermore, it will be found in some mills that the center discharge liner is held by bolts through the discharge head, whereas in other cases it depends upon the clamping effect of grates to hold it in position. In any event, the primary thing to remember in assembling the discharge grate head parts is the fact that the grate should be first drawn up tightly towards the center discharge liner by adjusting the grate set screws located at the periphery of the discharge head. This adjustment should be carried out in progressive steps, alternating at about 180 if possible and in such a manner that, the center discharge liner does not become dislodged from its proper position at the center of the mill. These grate set screws should be adjusted with the side clamp bar bolts loosened. After the grates have been completely tightened with the set screws, check for correct and uniform position of each grate section. The side clamp bar bolts may now be lightened, again using an alternate process. This should result in the side clamp bars firmly bearing against the beveled sides of the grates. The side clamp bars should not hear against the lifter liners.
When new pan liners are installed, they should be grouted in position so as to prevent pulp race in the void space between the discharge head and the pan liner. Another good method of preventing this pulp race is the use of the sponge rubber which can be cemented in place.
After the mill is erected, in order to avoid overlooking both obvious and obscure installation details, we recommend the use of a check list. This is particularly recommended for multiple mill installations where it is difficult to control the different phases of installation for each and every mill. Such a check list can be modeled after the following:
No. 1 Connecting Bolts drawn tight. A. Head and Shell flange bolts. B. Gear Connecting, bolts. No. 2 Trunnion studs or bolts drawn up tight. No. 3 Trunnion liner and feeder connecting bolts or studs drawn up tight. No. 4 Feeder lip bolts tightened. No. 5 Liner bolts drawn up tight. No. 6 Gear. A. Concentric B. Backlash C. Runout D. Joint bolts drawn up tight. No. 7 Coupling and Drive alignment and lubrication. No. 8 Bearings and Gearing cleaned and lubricated. No. 9 Lubrication system in working order with automatic devices including alarms and interlocking systems.
We further recommend that during the first thirty to sixty days of operation, particular attention be given to bolt tightness, foundation settlement and condition of the grouting. We suggest any unusual occurrence be recorded so that should trouble develop later there may be a clue which would simplify diagnosing and rectifying the situation.
As a safety precaution, and in many cases in order to comply with local safety regulations, guards should be used to protect the operators and mechanics from contact with moving parts. However, these guards should not be of such a design that will prevent or hinder the close inspection of the vital parts. Frequent inspection should be made at regular intervals with particular attention being given to the condition of the wearing parts in the mill. In this way, you will be better able to anticipate your needs for liners and other parts in time to comply with the current delivery schedules.
When ordering repair or replacement parts for your mill, be sure to identify the parts with the number and description as shown on the repair parts list, and specify the hand and serial number of the mill.
By following the instructions outlined in this manual, mechanical malfunctions will be eliminated. However, inadvertent errors may occur even under, the most careful supervision. With this in mind, it is possible that some difficulties may arise. Whenever any abnormal mechanical reactions are found, invariably they can be attributed to causes which though sometimes obvious are often hidden. We sight herewith the most common problems, with their solutions.
Cause A GROUT DISINTEGRATION. Very often when the grouting is not up to specification the vibration from the mill tends to disintegrate the grouting. In most instances the disintegration starts between the sole plate and the top surface of the grouting near or at the vertical centerline of the mill. As this continues, the weight of the mill causes the sole plate and trunnion bearing base to bend with a resultant pinching action at the side of the bearing near the horizontal center line of the mill. This pinching will cut off and wipe the oil film from the journal and will manifest itself in the same manner as if the lubrication supply had been cut off. If the grout disintegration is limited to about . 050 and does not appear to be progressing further, the situation can be corrected by applying a corresponding amount of shimming between the trunnion bearing base and the sole plate near the centerline of the mill in such a fashion that the trunnion bearing base has been returned to its normal dimensional position. If, on the other hand, the grouting is in excess of . 050 and appears to be progressing further, it is advisable to shut down operations until the sole plate has been re grouted.
Cause B HIGH SPOT ON THE BUSHING. While all BallMill bushings are scraped in the shop to fit either a jig mandrel or the head proper to which it is to be fitted, nevertheless there is a certain amount of seasoning and dimensional change which goes on in the type of metals used. Therefore if high spots are found, the mill should be raised, the bushings removed and rescraped. Bluing may be used to assist in detecting high spots.
Cause C INSUFFICIENT OIL FLOW. Increase the oil supply if it is a flood oil system. If brick grease is used, it is possible that the particular grade of brick may not be applicable to the actual bearing temperature. Refer to the remarks in this manual under the paragraph entitled Lubrication.
Cause E EXCESSIVE RUBBING ON THE SIDE OF THE BUSHING. This comes about due to the improper setting of the bearings in the longitudinal plane. In some cases, particularly on dry grinding or hot clinker grinding mills, the expansion of the mills proper may account for this condition. In any event, it can be remedied by re-adjusting the bearing base on the sole plate longitudinally at the end opposite the drive.
There are many more lubricant suppliers, such as E. F. Houghton and Co. , or Lubriplate Division of Fiske Bros. Refining Co. In making your final selection of lubricants, you should consider the actual plant conditions as well as the standardization of lubricants. New and improved lubricants are being marketed, and we, therefore, suggest that you consult your local suppliers.
The combination of Metso Minerals and Outotec has been completed and the new company, Metso Outotec, was established on July 1, 2020. At the same time, Metso Flow Control became a separately listed independent company and started its journey under the name of Neles.
The combination of Metso Minerals and Outotec is completed and the new company, Metso Outotec, started its journey.Metso Outotec is a frontrunner in sustainable minerals processing technologies, end-to-end solutions and services globally.The company helps aggregates, mining, metals refining and recycling customers improve efficiency, productivity and reduce risks.
Metso Flow Control has become a separately listed independent company called Neles. Neles is a flow control solutions and services provider for oil and gas refining, pulp, paper and the bioproducts industry, chemicals, and other process industries.The company's valves and valve automation technologies are known for quality, reliability and highest safety.
In all ore dressing and milling Operations, including flotation, cyanidation, gravity concentration, and amalgamation, the Working Principle is to crush and grind, often with rob mill & ball mills, the ore in order to liberate the minerals. In the chemical and process industries, grinding is an important step in preparing raw materials for subsequent treatment.In present day practice, ore is reduced to a size many times finer than can be obtained with crushers. Over a period of many years various fine grinding machines have been developed and used, but the ball mill has become standard due to its simplicity and low operating cost.
A ball millefficiently operated performs a wide variety of services. In small milling plants, where simplicity is most essential, it is not economical to use more than single stage crushing, because the Steel-Head Ball or Rod Mill will take up to 2 feed and grind it to the desired fineness. In larger plants where several stages of coarse and fine crushing are used, it is customary to crush from 1/2 to as fine as 8 mesh.
Many grinding circuits necessitate regrinding of concentrates or middling products to extremely fine sizes to liberate the closely associated minerals from each other. In these cases, the feed to the ball mill may be from 10 to 100 mesh or even finer.
Where the finished product does not have to be uniform, a ball mill may be operated in open circuit, but where the finished product must be uniform it is essential that the grinding mill be used in closed circuit with a screen, if a coarse product is desired, and with a classifier if a fine product is required. In most cases it is desirable to operate the grinding mill in closed circuit with a screen or classifier as higher efficiency and capacity are obtained. Often a mill using steel rods as the grinding medium is recommended, where the product must have the minimum amount of fines (rods give a more nearly uniform product).
Often a problem requires some study to determine the economic fineness to which a product can or should be ground. In this case the 911Equipment Company offers its complete testing service so that accurate grinding mill size may be determined.
Until recently many operators have believed that one particular type of grinding mill had greater efficiency and resulting capacity than some other type. However, it is now commonly agreed and accepted that the work done by any ballmill depends directly upon the power input; the maximum power input into any ball or rod mill depends upon weight of grinding charge, mill speed, and liner design.
The apparent difference in capacities between grinding mills (listed as being the same size) is due to the fact that there is no uniform method of designating the size of a mill, for example: a 5 x 5 Ball Mill has a working diameter of 5 inside the liners and has 20 per cent more capacity than all other ball mills designated as 5 x 5 where the shell is 5 inside diameter and the working diameter is only 48 with the liners in place.
Ball-Rod Mills, based on 4 liners and capacity varying as 2.6 power of mill diameter, on the 5 size give 20 per cent increased capacity; on the 4 size, 25 per cent; and on the 3 size, 28 per cent. This fact should be carefully kept in mind when determining the capacity of a Steel- Head Ball-Rod Mill, as this unit can carry a greater ball or rod charge and has potentially higher capacity in a given size when the full ball or rod charge is carried.
A mill shorter in length may be used if the grinding problem indicates a definite power input. This allows the alternative of greater capacity at a later date or a considerable saving in first cost with a shorter mill, if reserve capacity is not desired. The capacities of Ball-Rod Mills are considerably higher than many other types because the diameters are measured inside the liners.
The correct grinding mill depends so much upon the particular ore being treated and the product desired, that a mill must have maximum flexibility in length, type of grinding medium, type of discharge, and speed.With the Ball-Rod Mill it is possible to build this unit in exact accordance with your requirements, as illustrated.
To best serve your needs, the Trunnion can be furnished with small (standard), medium, or large diameter opening for each type of discharge. The sketch shows diagrammatic arrangements of the four different types of discharge for each size of trunnion opening, and peripheral discharge is described later.
Ball-Rod Mills of the grate discharge type are made by adding the improved type of grates to a standard Ball-Rod Mill. These grates are bolted to the discharge head in much the same manner as the standard headliners.
The grates are of alloy steel and are cast integral with the lifter bars which are essential to the efficient operation of this type of ball or rod mill. These lifter bars have a similar action to a pump:i. e., in lifting the product so as to discharge quickly through the mill trunnion.
These Discharge Grates also incorporate as an integral part, a liner between the lifters and steel head of the ball mill to prevent wear of the mill head. By combining these parts into a single casting, repairs and maintenance are greatly simplified. The center of the grate discharge end of this mill is open to permit adding of balls or for adding water to the mill through the discharge end.
Instead of being constructed of bars cast into a frame, Grates are cast entire and have cored holes which widen toward the outside of the mill similar to the taper in grizzly bars. The grate type discharge is illustrated.
The peripheral discharge type of Ball-Rod Mill is a modification of the grate type, and is recommended where a free gravity discharge is desired. It is particularly applicable when production of too many fine particles is detrimental and a quick pass through the mill is desired, and for dry grinding.
The drawings show the arrangement of the peripheral discharge. The discharge consists of openings in the shell into which bushings with holes of the desired size are inserted. On the outside of the mill, flanges are used to attach a stationary discharge hopper to prevent pulp splash or too much dust.
The mill may be operated either as a peripheral discharge or a combination or peripheral and trunnion discharge unit, depending on the desired operating conditions. If at any time the peripheral discharge is undesirable, plugs inserted into the bushings will convert the mill to a trunnion discharge type mill.
Unless otherwise specified, a hard iron liner is furnished. This liner is made of the best grade white iron and is most serviceable for the smaller size mills where large balls are not used. Hard iron liners have a much lower first cost.
Electric steel, although more expensive than hard iron, has advantage of minimum breakage and allows final wear to thinner section. Steel liners are recommended when the mills are for export or where the source of liner replacement is at a considerable distance.
Molychrome steel has longer wearing qualities and greater strength than hard iron. Breakage is not so apt to occur during shipment, and any size ball can be charged into a mill equipped with molychrome liners.
Manganese liners for Ball-Rod Mills are the world famous AMSCO Brand, and are the best obtainable. The first cost is the highest, but in most cases the cost per ton of ore ground is the lowest. These liners contain 12 to 14% manganese.
The feed and discharge trunnions are provided with cast iron or white iron throat liners. As these parts are not subjected to impact and must only withstand abrasion, alloys are not commonly used but can be supplied.
Gears for Ball-Rod Mills drives are furnished as standard on the discharge end of the mill where they are out of the way of the classifier return, scoop feeder, or original feed. Due to convertible type construction the mills can be furnished with gears on the feed end. Gear drives are available in two alternative combinations, which are:
All pinions are properly bored, key-seated, and pressed onto the steel countershaft, which is oversize and properly keyseated for the pinion and drive pulleys or sheaves. The countershaft operates on high grade, heavy duty, nickel babbitt bearings.
Any type of drive can be furnished for Ball-Rod Mills in accordance with your requirements. Belt drives are available with pulleys either plain or equipped with friction clutch. Various V- Rope combinations can also be supplied.
The most economical drive to use up to 50 H. P., is a high starting torque motor connected to the pinion shaft by means of a flat or V-Rope drive. For larger size motors the wound rotor (slip ring) is recommended due to its low current requirement in starting up the ball mill.
Should you be operating your own power plant or have D. C. current, please specify so that there will be no confusion as to motor characteristics. If switches are to be supplied, exact voltage to be used should be given.
Even though many ores require fine grinding for maximum recovery, most ores liberate a large percentage of the minerals during the first pass through the grinding unit. Thus, if the free minerals can be immediately removed from the ball mill classifier circuit, there is little chance for overgrinding.
This is actually what has happened wherever Mineral Jigs or Unit Flotation Cells have been installed in the ball mill classifier circuit. With the installation of one or both of these machines between the ball mill and classifier, as high as 70 per cent of the free gold and sulphide minerals can be immediately removed, thus reducing grinding costs and improving over-all recovery. The advantage of this method lies in the fact that heavy and usually valuable minerals, which otherwise would be ground finer because of their faster settling in the classifier and consequent return to the grinding mill, are removed from the circuit as soon as freed. This applies particularly to gold and lead ores.
Ball-Rod Mills have heavy rolled steel plate shells which are arc welded inside and outside to the steel heads or to rolled steel flanges, depending upon the type of mill. The double welding not only gives increased structural strength, but eliminates any possibility of leakage.
Where a single or double flanged shell is used, the faces are accurately machined and drilled to template to insure perfect fit and alignment with the holes in the head. These flanges are machined with male and female joints which take the shearing stresses off the bolts.
The Ball-Rod Mill Heads are oversize in section, heavily ribbed and are cast from electric furnace steel which has a strength of approximately four times that of cast iron. The head and trunnion bearings are designed to support a mill with length double its diameter. This extra strength, besides eliminating the possibility of head breakage or other structural failure (either while in transit or while in service), imparts to Ball-Rod Mills a flexibility heretofore lacking in grinding mills. Also, for instance, if you have a 5 x 5 mill, you can add another 5 shell length and thus get double the original capacity; or any length required up to a maximum of 12 total length.
On Type A mills the steel heads are double welded to the rolled steel shell. On type B and other flanged type mills the heads are machined with male and female joints to match the shell flanges, thus taking the shearing stresses from the heavy machine bolts which connect the shell flanges to the heads.
The manhole cover is protected from wear by heavy liners. An extended lip is provided for loosening the door with a crow-bar, and lifting handles are also provided. The manhole door is furnished with suitable gaskets to prevent leakage.
The mill trunnions are carried on heavy babbitt bearings which provide ample surface to insure low bearing pressure. If at any time the normal length is doubled to obtain increased capacity, these large trunnion bearings will easily support the additional load. Trunnion bearings are of the rigid type, as the perfect alignment of the trunnion surface on Ball-Rod Mills eliminates any need for the more expensive self-aligning type of bearing.
The cap on the upper half of the trunnion bearing is provided with a shroud which extends over the drip flange of the trunnion and effectively prevents the entrance of dirt or grit. The bearing has a large space for wool waste and lubricant and this is easily accessible through a large opening which is covered to prevent dirt from getting into the bearing.Ball and socket bearings can be furnished.
Scoop Feeders for Ball-Rod Mills are made in various radius sizes. Standard scoops are made of cast iron and for the 3 size a 13 or 19 feeder is supplied, for the 4 size a 30 or 36, for the 5 a 36 or 42, and for the 6 a 42 or 48 feeder. Welded steel scoop feeders can, however, be supplied in any radius.
The correct size of feeder depends upon the size of the classifier, and the smallest feeder should be used which will permit gravity flow for closed circuit grinding between classifier and the ball or rod mill. All feeders are built with a removable wearing lip which can be easily replaced and are designed to give minimum scoop wear.
A combination drum and scoop feeder can be supplied if necessary. This feeder is made of heavy steel plate and strongly welded. These drum-scoop feeders are available in the same sizes as the cast iron feeders but can be built in any radius. Scoop liners can be furnished.
The trunnions on Ball-Rod Mills are flanged and carefully machined so that scoops are held in place by large machine bolts and not cap screws or stud bolts. The feed trunnion flange is machined with a shoulder for insuring a proper fit for the feed scoop, and the weight of the scoop is carried on this shoulder so that all strain is removed from the bolts which hold the scoop.
High carbon steel rods are recommended, hot rolled, hot sawed or sheared, to a length of 2 less than actual length of mill taken inside the liners. The initial rod charge is generally a mixture ranging from 1.5 to 3 in diameter. During operation, rod make-up is generally the maximum size. The weights per lineal foot of rods of various diameters are approximately: 1.5 to 6 lbs.; 2-10.7 lbs.; 2.5-16.7 lbs.; and 3-24 lbs.
Forged from the best high carbon manganese steel, they are of the finest quality which can be produced and give long, satisfactory service. Data on ball charges for Ball-Rod Mills are listed in Table 5. Further information regarding grinding balls is included in Table 6.
Rod Mills has a very define and narrow discharge product size range. Feeding a Rod Mill finer rocks will greatly impact its tonnage while not significantly affect its discharge product sizes. The 3.5 diameter rod of a mill, can only grind so fine.
Crushers are well understood by most. Rod and Ball Mills not so much however as their size reduction actions are hidden in the tube (mill). As for Rod Mills, the image above best expresses what is going on inside. As rocks is feed into the mill, they are crushed (pinched) by the weight of its 3.5 x 16 rods at one end while the smaller particles migrate towards the discharge end and get slightly abraded (as in a Ball Mill) on the way there.
We haveSmall Ball Mills for sale coming in at very good prices. These ball mills are relatively small, bearing mounted on a steel frame. All ball mills are sold with motor, gears, steel liners and optional grinding media charge/load.
Ball Mills or Rod Mills in a complete range of sizes up to 10 diameter x20 long, offer features of operation and convertibility to meet your exactneeds. They may be used for pulverizing and either wet or dry grindingsystems. Mills are available in both light-duty and heavy-duty constructionto meet your specific requirements.
All Mills feature electric cast steel heads and heavy rolled steelplate shells. Self-aligning main trunnion bearings on large mills are sealedand internally flood-lubricated. Replaceable mill trunnions. Pinion shaftbearings are self-aligning, roller bearing type, enclosed in dust-tightcarrier. Adjustable, single-unit soleplate under trunnion and drive pinionsfor perfect, permanent gear alignment.
Ball Mills can be supplied with either ceramic or rubber linings for wet or dry grinding, for continuous or batch type operation, in sizes from 15 x 21 to 8 x 12. High density ceramic linings of uniform hardness male possible thinner linings and greater and more effective grinding volume. Mills are shipped with liners installed.
Complete laboratory testing service, mill and air classifier engineering and proven equipment make possible a single source for your complete dry-grinding mill installation. Units available with air swept design and centrifugal classifiers or with elevators and mechanical type air classifiers. All sizes and capacities of units. Laboratory-size air classifier also available.
A special purpose batch mill designed especially for grinding and mixing involving acids and corrosive materials. No corners mean easy cleaning and choice of rubber or ceramic linings make it corrosion resistant. Shape of mill and ball segregation gives preferential grinding action for grinding and mixing of pigments and catalysts. Made in 2, 3 and 4 diameter grinding drums.
Nowadays grinding mills are almost extensively used for comminution of materials ranging from 5 mm to 40 mm (3/161 5/8) down to varying product sizes. They have vast applications within different branches of industry such as for example the ore dressing, cement, lime, porcelain and chemical industries and can be designed for continuous as well as batch grinding.
Ball mills can be used for coarse grinding as described for the rod mill. They will, however, in that application produce more fines and tramp oversize and will in any case necessitate installation of effective classification.If finer grinding is wanted two or three stage grinding is advisable as for instant primary rod mill with 75100 mm (34) rods, secondary ball mill with 2540 mm(11) balls and possibly tertiary ball mill with 20 mm () balls or cylpebs.To obtain a close size distribution in the fine range the specific surface of the grinding media should be as high as possible. Thus as small balls as possible should be used in each stage.
The principal field of rod mill usage is the preparation of products in the 5 mm0.4 mm (4 mesh to 35 mesh) range. It may sometimes be recommended also for finer grinding. Within these limits a rod mill is usually superior to and more efficient than a ball mill. The basic principle for rod grinding is reduction by line contact between rods extending the full length of the mill, resulting in selective grinding carried out on the largest particle sizes. This results in a minimum production of extreme fines or slimes and more effective grinding work as compared with a ball mill. One stage rod mill grinding is therefore suitable for preparation of feed to gravimetric ore dressing methods, certain flotation processes with slime problems and magnetic cobbing. Rod mills are frequently used as primary mills to produce suitable feed to the second grinding stage. Rod mills have usually a length/diameter ratio of at least 1.4.
Tube mills are in principle to be considered as ball mills, the basic difference being that the length/diameter ratio is greater (35). They are commonly used for surface cleaning or scrubbing action and fine grinding in open circuit.
In some cases it is suitable to use screened fractions of the material as grinding media. Such mills are usually called pebble mills, but the working principle is the same as for ball mills. As the power input is approximately directly proportional to the volume weight of the grinding media, the power input for pebble mills is correspondingly smaller than for a ball mill.
A dry process requires usually dry grinding. If the feed is wet and sticky, it is often necessary to lower the moisture content below 1 %. Grinding in front of wet processes can be done wet or dry. In dry grinding the energy consumption is higher, but the wear of linings and charge is less than for wet grinding, especially when treating highly abrasive and corrosive material. When comparing the economy of wet and dry grinding, the different costs for the entire process must be considered.
An increase in the mill speed will give a directly proportional increase in mill power but there seems to be a square proportional increase in the wear. Rod mills generally operate within the range of 6075 % of critical speed in order to avoid excessive wear and tangled rods. Ball and pebble mills are usually operated at 7085 % of critical speed. For dry grinding the speed is usually somewhat lower.
The mill lining can be made of rubber or different types of steel (manganese or Ni-hard) with liner types according to the customers requirements. For special applications we can also supply porcelain, basalt and other linings.
The mill power is approximately directly proportional to the charge volume within the normal range. When calculating a mill 40 % charge volume is generally used. In pebble and ball mills quite often charge volumes close to 50 % are used. In a pebble mill the pebble consumption ranges from 315 % and the charge has to be controlled automatically to maintain uniform power consumption.
In all cases the net energy consumption per ton (kWh/ton) must be known either from previous experience or laboratory tests before mill size can be determined. The required mill net power P kW ( = ton/hX kWh/ton) is obtained from
Trunnions of S.G. iron or steel castings with machined flange and bearing seat incl. device for dismantling the bearings. For smaller mills the heads and trunnions are sometimes made in grey cast iron.
The mills can be used either for dry or wet, rod or ball grinding. By using a separate attachment the discharge end can be changed so that the mills can be used for peripheral instead of overflow discharge.