Rod Mills

Cement Grinding

The principle of Grate Discharge grinding is nearly universally adapted in the cement grinding industry. Grate Discharge Ball Mills are the rule rather than the exception. Rod Mills for raw and finish grinding begin to enter the picture. Larger and larger diameter mills become common. Lengths tend to shorten. Cement grinding using Grate Discharge principles developed in the ore milling industry applied to the cement industry. This experience plus the years of manufacturing know how unquestionably qualify Grate Discharge grinding for the Cement Industry.

RAW CEMENT GRINDING

This phase of grinding may be either the wet or dry process, the end product going to a kiln. Material ground consists of limestone, cement rock, marl or marine shells along with secondary materials usually shale or clay. A typical raw mix consists of 75-85% limestone, 12-25% shale, the balance consisting of silica or quartzite and iron oxide. Exact proportioning is dependent upon their chemical properties before and after calcining to cement clinker. For good kiln practice the grind required is 88-92% – 200 mesh for standard cement, 99%-200 mesh for high early. Uniform kiln feed size helps reduce tendency to form kiln rings.

WET VS DRY Grinding of Cement

Wet grinding is generally more efficient ….Read more

Comminution Theory & Process Equipment

This page is devoted to the subject “From the Comminution Theory to Practice by selection of the correct Process Equipment” by taking you step by step through some of the variables encountered in the specific part of Comminution called grinding and how each of these affect your operations. Should it be possible to reduce all of these variables to a simple mathematical formula the selection of a grinding mill would, of course, be simple. Many approaches to this have been made but to date a foolproof formula, both mathematically and practically applicable, has not been devised. We must, therefore, take each variable into consideration on its own merits and then correlate such ideas into a single selection. To do this a broad experience and understanding of the complete subject of grinding is essential. This is a part of the problem of your engineers and our own consulting staff. General points have been discussed briefly on wet or dry grinding, and fineness of grind. Two main categories of grinding equipment, namely rod mills and ball mills, have also been mentioned. Whether grinding is to be performed wet or dry, or in a ball mill or rod mill, a choice must be made between open ….Read more

Grinding Balls & Rods

The subject of grinding media (grinding balls & grinding rods) is still controversial. The following information is general and based upon facts gathered from many operations.

General statements can be made and are worthy of consideration when selecting grinding media. For the best results it has been found that the smallest diameter ball or rod which will break down the particular material to be ground is desirable since greatest surface area is obtained. From the standpoint of economy, the larger the media the higher will be the liner consumption and media consumption. The minimum size of grinding balls should be selected with caution since there will be a tendency for such balls to float out of the mill in a dense pulp (this is minimised by the use of a grate discharge mill). Also the smaller the media the quicker it will reach its reject size.grinding_balls

For the first stage of grinding, media will generally be in the 4″ to 2″ size (in some cases as high as 5″). In secondary finer grinding the initial charge will begin at around 3″ and in the case of balls will grade down to about ¾”. ….Read more

Industrial Ball Mills

A symbol of dependable quality ore milling machinery manufacturing, industrial and mining equipment, ball mills and rod mills as well as supplies created for your specific needs. During this period thousands of operators have experienced continuous economical and unequalled service through their use. As an industrial ball mill manufacturer and supplier, we have continuously accumulated knowledge on grinding applications. It has contributed greatly to the grinding process through the development and improvement of such equipment.

Just what is grinding? It is the reduction of lump solid materials to smaller particles by the application of shearing forces, pressure, attrition, impact and abrasion. The primary consideration, then, has been to develop some mechanical means for applying these forces. The modern grinding mill applies power to rotate the mill shell and thus transmits energy to some form of media which, in turn, fractures individual particles.PEBBLE MILLS

Through constant and extensive research, in the field of grinding as well as in the field of manufacturing. Constantly changing conditions provide a challenge for the future. Meeting this challenge keeps our company young and progressive. This progressive spirit, with the knowledge gained through the years, assures top quality equipment for the users of our mills.

Today modern manufacturing ….Read more

Rod Mill & Ball Mill Manufacturer & Supplier of Grinding Mills

All Ball Mill Manufacturers understand the object of the grinding process is a mechanical reduction in size of crushable material. Grinding can be undertaken in many ways. The most common way for high capacity industrial purposes is to use a tumbling charge of grinding media in a rotating cylinder or drum. The fragmentation of the material in that charge occurs through pressure, impact, and abrasion.

Grinding is converting energy. When the grinding charge is forced to tumble the motor energy is converted into new particle surface and heat.

An important point for the economy is that the size of the grinding media suits the material to be ground.

The choice of mill design depends on the particle size distribution in the feed and in the product wanted. Often the grinding is more economic when executed in a primary step, followed by a secondary step, giving a fine size product.

As experts in crushing and grinding – can offer a full range of grinding mill types and sizes. Our mills are identified by codes of letters:

C=central trunnion discharge
P=peripheral dischargeball-mill-manufacturer
R=spherical roller trunnion bearing, feed end
H=hydrostatic shoe bearing, feed end
R=spherical roller trunnion bearing, discharge ….Read more

Grinding Mills: Ball Mill & Rod Mill Design & Parts

Common types of grinding mills include Ball Mills and Rod Mills. This includes all rotating mills with heavy grinding media loads.  This article focuses on ball and rod mills excluding SAG and AG mills. Although their concepts are very similar, they are not discussed here.

Photographs of a glass ended laboratory ball mill show action of ball mass within the mill. The action of other grinding media is similar.

As the mill revolves, lifters assist in picking up the grinding charge and elevate it to an angle at which gravity overcomes friction and centrifugal force. The charge then cascades downward, effectively grinding particles of material within the mill by continuous, repeated impact and attrition action.

Grinding Mill RPM – Rotating Speed

Grinding Mill speed is one of the factors affecting the character of the cascading charge. As shown in the illustrations, the lower the percentage of critical speed, the smoother the flow of balls from top of charge to bottom. Higher percentage of critical speed is used for impact grinding of large feed. Lower percentage of critical speed is used for attrition grinding when a fine product is desired. The graph below will be helpful in determining percentage of critical speed when internal ….Read more

Rod Mills

The Steel Head Rod Mill (sometimes call a bar mill) gives the ore dressing engineer a very wide choice in grinding design. He can easily secure a standard Steel Head Rod Mill suited to his particular problem. The successful operation of any grinding unit is largely dependent on the method of removing the ground pulp. The Steel Head Rod Mill is available with five types of discharge trunnions and each type trunnion is available in small, medium, or large diameter. The types of Rod Mill discharge trunnions are:

  1. overflow,
  2. perforated overflow,
  3. return spiral,
  4. grate, and
  5. peripheral.

Thus the engineer can fit any one of fifteen variations of sizes and type of discharging a rod mill, into the problem on which he is working.

The superiority of the Steel Head Rod Mill is due to the all-steel construction. The trunnions are an integral part of the cast steel heads and are machined with the axis of the mill. The mill heads are insured against breakage due to the high tensile strength of cast steel as compared to that of the cast iron head found on the ordinary rod mill. Trunnion Bearings are made of high-grade nickel babbitt, dovetailed into the casting. Ball and socket bearings ….Read more

Small Ball Mills

A PULP level sufficiently high to interpose a bed of pulp, partly to cushion the impact of the balls, permits a maximum crushing effect with a minimum wear of steel. The pulp level of these Small Ball Mills can be varied from discharging at the periphery to discharging at a point about halfway between the trunnion and the periphery. The mill shell is of welded plate steel with integral end flanges turned for perfect alignment, and the heads are semi-steel, with hand holes in the discharge end through which the diaphragm regulation is arranged with plugs. The trunnion bearings are babbitted, spherical, cast iron, and of ample size to insure low bearing pressure; while the shell and saddle are machined to gauge so that the shells are interchangeable.

Small Ball Mill Capacity Table

Data based on:—Wet grinding, single stage, closed circuit operation: feed:—(½” one way dimension); Class III ore.
All mills:—free discharge, grated type, rapid pulp flow.
N. B.—for overflow type mills: capacity 80%—power 83%.
Dimensions :—“diameters” inside shell without liners—“lengths” working length shell between end liners.small-ball-mill-capacity

SMALL C. I. W. BALL MILL

The CIW is a Small Ball Mill that’s belt driven, rigid bearing, wet grinding, trunnion ….Read more

Ball Mill & Rod Mill Design

In all ore dressing and milling processes, including flotation, cyanidation, gravity concentration, and amalgamation, it is necessary 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.

GRINDING MILLS

Ball mills efficiently perform 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 ….Read more

Bond Rod Mill Work Index Equipment & Apparatus Review

Commentary on the apparatus of the Bond rod mill Work Index

by Alex Doll
December, 2015
alex.doll@sagmilling.com

The Bond “Third Theory” of comminution was originally divided into three size classes reflecting the varieties of comminution equipment common during the time period when Bond (and his collaborators) were gathering the information to calibrate comminution models.  The middle size class, represented by rod milling, is fitted to a tumbling test, referred to as the Bond rod mill work index (WiRM, or RWi).  The apparatus used to determine this work index was described in 1943 by Bond & Maxton.  The author has noted there are some laboratories that have deviated from the apparatus specified by Bond & Maxton and there are modern comminution models that are calibrated to this non-standard mill geometry.

Introduction

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The specification for the apparatus to determining a “Bond” rod mill work index is first described in Bond & Maxton (1943).  It states that the apparatus is a tumbling rod mill to be operated in a locked cycle test at a fixed circulating load.  The geometry of the grinding chamber is described as:

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