Rules when operating the overflow ball mill

The ball mill is essential part in beneficiation, and it is very important in crushing process. The main types of ball mills are: energy saving cone ball mill, grid ball mill, tubular ball mill, rotary bearing ball mill, etc. Henan Yuhui will introduce operation rules, maintenance and repair regulations of overflow ball mill to the customers’ reference.

 

I.  Carefully check the machine before starting it. For example, check whether the bolt is loose, the lubrication is in good condition, the driving devices are stable, the protective devices are in good condition, the instrument panel is sensitive and the carbon brush is in good connection.

II.  Carefully check whether there are obstructions around the driving part. Don’t allow people near the machine when starting the grinding machine.

III. Start the motor when there are not something wrong, and notice the change of current. The start times can not exceed 2 continuously. The internal can not be more than 5 minutes.

IV. Strictly in accordance with the rules of supplying water, feeding materials and adding steel balls. The idling time can not exceed 15 minutes to avoid broking the linear.

V. Check whether occurs leakage of slurry when operating. Carefully notice current, voltage. feeding, water supply. Check the motor and main shaft’ temperature every half hour. Ensure the temperature can not be more than 60℃.

VI. Stop feeding before stopping the ball mill, and then stop supplying water after the concentrate is discharged in the machine. Press the button and pull down the switch.

VII. When there is a power cut, fist pull down the switch, and press the button, then stop feeding and supplying water.

VIII. Clean the machine after stopping to ensure a clean environment.

Closed-circuit systems of cement ball mill

The efficiency of the early stages of grinding in a ball mill is much greater than that for formation of ultra-fine particles, so ball mills operate most efficiently by making a coarse product, the fine fractions of this then being separated, and the coarse part being returned to the mill inlet. 

 

The proportion of the mill-exit material returned to the inlet may vary from 10-30% when ordinary cement is being ground, to 85-95% for extremely fine cement products. It is important for system efficiency that the minimum amount of material of finished-product fineness is returned to the inlet. Modern separators are capable of making a very precise size "cut" and contribute significantly to the reduction of energy consumption, and have the additional advantage that they cool both the product and the returned material, thus minimizing over-heating.

 

Efficient closed-circuit systems, because of their tight particle size control, lead to cements with relatively narrow particle size distributions (i.e. for a given mean particle size, they have fewer large and small particles). This is of advantage in that it maximizes the strength-production potential the clinker, because large particles are inert. As a rule of thumb, only the outer 7 μm "skin" of each particle hydrates in concrete, so any particle over 14 μm diameter always leaves an un-reacted core. However, the lack of ultra-fine particles can be a disadvantage. 

These particles normally pack the spaces between the larger particles in a cement paste, and if absent the deficit is made up with extra water, leading to lower strength. This can be remedied by including 5% calcium carbonate in the cement: this soft mineral produces adequate ultra-fines on the first pass through the mill.

Industrial use of crusher

In industry, crushers are machines which use a metal surface to break or compress materials. Mining operations use crushers, commonly classified by the degree to which they fragment the starting material, with primary and secondary crushers handling coarse materials, and tertiary and quaternary crushers reducing ore particles to finer gradations. Each crusher is designed to work with a certain maximum size of raw material, and often delivers its output to a screening machine which sorts and directs the product for further processing. Typically, crushing stages are followed by milling stages if the materials need to be further reduced. Crushers are used to reduce particle size enough so that the material can be processed into finer particles in a grinder. A typical circuit at a mine might consist of a crusher followed by a SAG mill followed by a ball mill. In this context, the SAG mill and ball mill are considered grinders rather than crushers.

 

In operation, the raw material (of various sizes) is usually delivered to the primary crusher's hopper by dump trucks, excavators or wheeled front-end loaders. A feeder device such as a conveyor or vibrating grid controls the rate at which this material enters the crusher, and often contains a preliminary screening device which allows smaller material to bypass the crusher itself, thus improving efficiency. Primary crushing reduces the large pieces to a size which can be handled by the downstream machinery.

Some crushers are mobile and can crush rocks (as large as 16 inches), concrete and asphalt into material as it is driven over material on road surface, thus removing the method of hauling oversized material to a stationary crusher and back to road surface. They are used, for example in road constructions.

Flotation Process Theory

An entirely unnecessary veil of mystery has been suffered to obscure the theoretical side of flotation processes. The forces involved, it is true, are not of such common cognizance as are those in the older methods of gravity concentration, but they are no more wonderful or mysterious in the one case than in the other. 

 

The forces utilized are finite in the range of their manifestations, but we have to appeal to molecular considerations for a complete exposition. The imagination of professional engineers is so well trained in these days that they should have no difficulty in grasping the significance of most of the observed facts, and there is, therefore, no reason why anybody engaged in metallurgical pursuits should not become as familiar with these methods of ore treatment as with any other ball mill.

 

A few analogies may be instanced in order to inspire confidence and allay the well established fear of the mysterious. For example, the amalgamation treatment of gold ores, wherein crushed ore, water, and quicksilver are mixed in proper proportions and in suitable devices, is so well known, and metallurgists have become so familiar with it, that the wonderful and obscure molecular reactions between the gold and the quicksilver are never given any thought. 

 

Again, the chemical reactions characterizing the cyanide treatment of gold ores, though we are in a measure able to quantify them by a familiar symbolism, require an undoubted exercise of the imagination by means of a written or mental picture of KCy -f Au = KAuCy. So in the case of flotation-concentration processes the physical laws are for the most part plain ; and where obscure, the obscurity is not a matter that need obstruct practical application. It is not my purpose to enter into a mathematical or physical discussion of the laws regulating these forces. 

 

James Clerk Maxwell, in his classical article on ' Capillary Action,' in the ninth edition of the Encyclopedia Britannica, has laid the foundation for a mathematic demonstration of all the phenomena involved ; moreover H. Livingstone Sulman and Hugh F. K. Picard have in preparation a full dissertation on the observed facts of surface tension and oleaginous and gas-film adhesion, with special reference to their bearing upon concentration by flotation. Sulman & Picard's essay is a document of the highest scientific quality, and we have had a pleasant foretaste of its merit in Sulman's recent announcement of the hysteresis range of the contact angle.

 

My purpose is to give a description in plain and simple language of what takes place when a particle of mineral floats at the surface of a liquid, leaving the mathematical and molecular aspects of the subject to be discussed at some future time.

 

Unfortunately, the nomenclature hitherto adopted in discussing the laws and principles governing flotation processes has not been such that it carried any explanation with it, but it is the better part of wisdom not to attempt to introduce new terms. I must confess to an inexplicable dislike of the term, ' surface tension,' a dislike that dates from my undergraduate days in the physical laboratory.

Mining Industry in Pakistan

Pakistan is endowed with significant mineral resources and emerging as a very promising area for prospecting/exploration of mineral deposits. Bases on available information, the country's more than 6,00,000 km² of outcrops area demonstrates varied geological potential for metallic and non-metallic mineral deposits. Except oil, gas and nuclear minerals regulated at federal level, Minerals are a provincial subject, under the constitution of Islamic Republic of Pakistan. Provincial governments are responsible for development and exploitation of minerals, besides, enforcing regulatory regime. In line with the constitutional framework the federal and provincial governments have jointly set out Pakistan first National Mineral Policy in 1995, duly implemented by the provinces, providing appropriate institutional and regulatory framework and equitable and internationally competitive fiscal regime.

 

In the recent past, exploration by government agencies as well as by multinational mining companies presents ample evidence of the occurrences of sizeable minerals deposits. Recent discoveries of a thick oxidized zone underlain by sulphide zones in the shield area of the Punjab province, covered by thick alluvial cover have opened new vistas for metallic minerals exploration. Pakistan has large base for industrial minerals. The discovery of coal deposits having over 175 billion tones of reserves at Thar in the Sindh province has given an impetus to develop it as an alternate source of energy. There is vast potential for precious and dimension stones.

 

The enforcement of Mineral Policy (1995) has paved way to expand mining sector activities and attract international investment in this sector. International mining companies have responded favorably to the NMP and presently at least four are engaged in mineral projects development.

 

Currently about 52 minerals ball mills are under exploitation although on small scale. The major production is of coal, rock salt and other industrial and construction minerals. The current contribution of mineral sector to the GDB is about 0.5% and likely to increase considerably on the development and commercial exploitation of Saindak & Reco Diq copper and gold deposits (world largest gold mine), Duddar zinc lead, Thar coal and gemstone deposits.

Rock Crusher Maintenance

Know When It Is Going To Go Down

 

Just as is the case with almost anything, the most likely time that rock crushers break down is when you will need to get the most out of them. As it is, you never realize how important something is until you do not have it, or when it is most required. In order to skirt high repair costs and production loss, proper periodical maintenance of rock crushers is required. The most logical thing to do in order to maximize the crusher life is to establish and execute a plan that will increase the life of the crusher thereby reducing repair cost and increasing the output. This can be done through laying down a rock crusher maintenance schedule that is adhered to. Following are five steps to help achieve the goal.

 

1. Know and follow the Rock Crusher Constraints

 

Every machine has a few reservations and this applies to a rock crusher as well. There are basically three limitations that are particularly important to be kept in mind while operating a crusher i.e. the horsepower, volume, and the crushing force. It is an overload if any one of these limitations is exceeded during operation. The operator needs to take into consideration the type of rock being crushed and environmental conditions as this too may change the rock crusher's limits on the fly. By forcing the crusher to go beyond limits and stressing out different aspects of the machine, the lifespan is decreased and the time that it has between repairs and failure is shortened. All this leads to more repair expenditure, more man-hours, reduced output and in few cases permanent failure of the machine.

 

2. Familiarize yourself with the Maintenance Needs of your Rock Crusher

 

As with all the mechanical machines, maintenance is needed and must be followed. Rock Crushers are no different. There are three types of maintenance that one must follow to properly maintain the crusher. They are - Preventive maintenance, Predictive maintenance and Reactive maintenance.

• Preventive Maintenance

This type of crusher maintenance plan need to be on a schedule and followed to keep up the crusher life. Following the manufacturer's maintenance manual should be the rule in this case. This includes looking after the components like crusher liners and other wearing components for their good health.

By not changing the liners in the crusher as they become less and less efficient, you will not only be losing money because of poor/out of spec product but also on labor as well since the operator will still be there for the same amount of time, but doing much less crushing. Also, the out of spec or oversized material may re-circulate in a closed circuit to further increase the load on the already deficient crusher.

• Predictive Maintenance

This refers to monitoring the condition of the rock crusher while it is in use. This is done by using predictive maintenance tools, such as lubricating oil thermometers, lube oil pressure gauges, lubricating oil filter condition indicator device, lube oil analysis, crusher drive motor ammeter and daily operator crusher log sheets. These are used to determine the normal operating specs of the crusher. This will allow seeing when things are not running properly and allow proper and corrective action to occur.

• Reactive Maintenance

This maintenance occurs when the crusher is not operating properly and it is decided it is time to fix. In other words, waiting until it is broken in order to maintain it. This should be seen as the last resort and be avoided.

 

3. Root Cause Analysis

 

Identify and apply corrective measures to the root cause because of which the rock crusher is facing issues. This can be very cost effective in the long run as it will minimize the reoccurrence of the problem. Root cause analysis not only helps in curbing the current problem but also in forecasting the potential of an incident. Thus corrective measures can be implemented well in advance.

 

There are many different techniques and tools for conducting root cause analysis like gathering data, checking the operator's skills and knowledge, inspection of the machine and end product, machine placement, forces of nature, maintenance processes etc. Once the root cause is identified, establish the corrective measure plan which will best suit to achieve your goals. The tracking of corrective measures can be documented in the form of dash-boards for the staff.

 

4. Design and Implement an Employee Training Plan

 

Many problems that would occur with a rock crusher can be prevented if employees are trained properly. Employees can be trained on one-to-one basis or through a group session. Group sessions are more advisable if a new technique or process has to be imparted to employees. Employee training program should be designed in such a manner that it keeps in mind each employee's needs and current skill status.

Proper training of employees increases their morale, confident in operating the crusher, their efficiency to work and decreases employee turnover. Which in turn lead to better working machine and an increase in profit over the long run. Employee training is not a one time job rather it should be done periodically so that each person is well equipped with the correct and updated knowledge of operating and maintenance of the rock crusher.