Lyntas/mining_domain_knowledge_reference_dataset huggingface dataset:
Area: Minning Maintenance Realibility
REAGENT MIXING AND DOSING 
No checking of solution strength and clarity was been carried out which ultimately led to varying strengths of reagent and crystals of PAX and SIPX frequently blocking the reagent dosing lines. The frequency of blockages was at least one reagent line per shift with catastrophic effects
Line blockages occurred more frequently immediately after reagent mixing. The mixing tank feed hopper had no trash screen. Reagent dosing was via manually controlled valves placed on horizontal manifold being fed directly from the holding tank. Due to the lack of attention to reagent strength and particularly reagent crystal dissolution, solids were being introduced into the dosing system with disastrous consequences. The lack of good reagent pumping system compounded the problem.
The mixing tanks were fitted with new hoppers with integral trash screens and the re-circulation stream was re-routed so that it poured onto the trash screen thus enabling lumps of crystalline Xanthate to be washed through the screen, reducing the risk of blockages.
Area: Minning Maintenance Realibility
HYDROCYCLONE 
HYDROCYCLONE MAINTENANCE 
As mentioned previously, another source of plant instability was lack of preventative maintenance to hydro cyclones,
The mechanical department according to their scheduled plans was regularly carrying out maintenance; the problem was that this procedure had no metallurgical input as to when and why the internal components should be changed. The only occasion that the operational group became aware of a problem was when the flotation cell dart valves regularly blocked and the false bottoms below the Wemco cells eventually filled up with sand which subsequently scaled to a proud concrete mix and resulted in very poor cell recirculation of pulp requiring air lances to free up tanks etc.
As a consequence, the mechanical department would assume that provided the hydrocyclone had a rubber lining and the vortex finder was not holed,
Therefore, hydrocyclone vortex finders regularly holed (see Figure 17 below), and the rubber internals were being changed as the mechanical department saw fit, but this left significant steps in the joints between the new and old components which caused turbulence, increased wear and generated coarser overflow size distributions than necessary.
Area: Minning Maintenance Realibility
Another common wear pattern observed on vortex finders in particularly onerous duties is the cutting of the vortex finder around its base which if left unchecked can ultimately result in the vortex finder actually falling off into the hydrocylone vessel itself. This phenomenon is most usually associated with lack of attention to cover plate liner wear.
Once the cover plate liner becomes worn around the vortex finder, is creates a strong swirling action locally in this area and rapidly reduces vortex finder life.
As a consequence of the above, the metallurgical group were made responsible for managing hydrocylone maintenance working with the mechanical department. It soon became clear that vortex finder life was circa 3 months with new cover plate liners. The increased focus in this area resulted in a steady flotation feed size distribution and minimized instability within the flotation plant.
Area: Minning Maintenance Realibility
Thickeners
The object of a control system on a High Rate Thickener (HRT), as on a conventional thickener, is to obtain the required underflow density and overflow clarity at all feed conditions.
Thickening technology utilizes the principle of sedimentation as a cost effective method of solid-liquid separation.
Sedimentation is used to thicken an incoming feed stream to produce two phases:
 Overfl ow - a stream containing minimal solids
 Underfl ow - a stream containing minimal liquid

This is accomplished by a number of means inside the thickener:
 Settling under the force of gravity
 Addition of reagents such as flocculants, which are mixed with the incoming feed to enhance gravity settling such that it occurs faster or at a higher rate
 Bed compression due to self-weight of material in the settled bed
 Mechanical raking to release water trapped in the settled bed
Area: Minning Maintenance Realibility
Critical to thickener performance are two parameters:
1. Solids loading based on dry tonnes of solid entering the feedwell
2. Rise rate based on the flow rate (cubic meters per hour) entering the thickener including dilution water

Consequently, improvements in thickener process performance typically include efforts directed at improving the feed system, from upstream of the thickener through to the feedwell.
Thickeners are low-maintenance, designed as critical equipment, and generally have no duty standby installed. As they age, more focus must be placed on them to allow continuous operation.
When the existing tank satisfies the new requirements, modernizing the thickener is an attractive and often economically optimal method to extend the life of equipment or manage changed process scenarios.
Assuming the tank diameter and condition are suitable for increased loads, upgrades are possible to all other elements. Sidewall height can be extended, overflow capacity can be increased with new launders and/or new overflow boxes, floor angle can be increased, and underflow arrangements can be modified.
For old-style conventional thickeners, conversion to a High Rate Thickener (HRT) should be an early priority. HRTs allow for higher solids loading than conventional thickeners by efficiently using flocculation. Computational fluid dynamic (CFD) modeling and other research to improve the understanding of the complex and multiphase fluid flow behavior that occurs in feedwells
Feed pipe size, elevation changes and dilution requirements all need to be considered in upgrading a thickener feedwell.
Often modernization will add weight, either due to larger or additional installed components as in the case of forced dilution. The impact of this weight on the bridge structure must be considered. The modernization may include reinforcing or replacing bridge elements.
Area: Minning Maintenance Realibility
The drive unit consists of the base supporting structure, hydraulic motor mounts, pinion gears, slew ring gear, cage adapter ring and cage structure. Six motors are used to provide the drive action
Area: Minning Maintenance Realibility
F-Type Primary Speed Reducer
DBS Manufacturing, Inc. pioneered the concept of using hydraulics as the means of primary speed reduction on clarifier and thickener drive units. DBS incorporated the hydraulic speed reducer on its drive units in the early 1990s and it is now a standard feature on nearly all DBS drives. These primary speed reducers incorporate a hydraulic pump and motor fully enclosed in a reservoir for clean operation. 
Speed reduction: Many reduction ratios are available.
Torque limiting: Maximum torque cannot be exceeded. Once maximum torque is reached, the drive will slow down but still maintain torque. This is analogous to a truck shifting into lower gears when pulling a load up a hill.
Low maintenance: Change oil filter every three months.
Long life: Hydraulic components have been proven to last for years in continuous duty industrial clarifier and thickener applications.
Easy repair: All components can be removed with common hand tools. No special skills or training is required to maintain the unit. Most items can be replaced with alternate brands.
Reversibility: An optional directional control valve can provide easy reversing to allow clarifier or thickener rakes to be backed out of an overload condition. Torque overload protection is maintained when operating in reverse.
The main features of the F-type primary speed reducer are its reliability and its ability to operate at high torque in or near a stall mode. In a high-load, over-torque situation, the F-type primary speed reducer will keep the clarifier or thickener operating if at all possible. If the rakes are truly stuck, the F-type primary speed reducer will simply stall at a high, but safe, torque.
The operation of the F-type primary speed reducer is simple. The electric motor drives a hydraulic pump that delivers oil to a hydraulic motor. The hydraulic motor drives the output drive shaft of the F-type primary speed reducer. The displacement of the pump is much smaller than the displacement of the motor. This difference in displacement between hydraulic pump and motor results in speed reduction. A pressure relief valve provides torque-limiting protection.
Since the system pressure is directly proportional to the torque load, the torque gauge and switches operate by monitoring the system pressure. This provides an accurate torque reading and a pressure signal that can be used to drive a 4-20 mA torque transducer.
Area: Minning Maintenance Realibility
Drive
The drive is a single multi?stage planetary extra heavy duty unit driven via a hydraulic motor. The hydraulic drive minimises any shock loads at start?up (essentially a soft start), thereby minimising the wear on gearboxes and extending the drives service life.
Hydraulic pressure provides a simple and accurate means for monitoring and limiting rake torque. Using a pressure transmitter a 4?20 mA signal is provided for local and remote torque indication and control.
Area: Minning Maintenance Realibility
Power Pack
The thickener will be installed with a power?pack mounted on the bridge for ease of maintenance.
Area: Minning Maintenance Realibility
Rake Lift  
The unique design of our lifting device has eliminated all operational problems with lifting the rakes out of high torque situations effortlessly.
The lifting mechanism consists of a hydraulic cylinder driven by a hydraulic pump. The lift offered is 300mm for these units. The rake lift raise and lower operation can be actuated manually or automatically.
Area: Minning Maintenance Realibility
Concentrate thickener feed well upgrade
Issues
Severely corroded
Pipework not plumed into tangential inlet
No dispersion of mixed product into the thickener
Objectives
Reduce loss of concentrate to the overflow
Replace feed wells with improved design
Utilize available process control equipment

Design Criteria
Minimise aeration of slurry
Reduce velocity of slurry entering feed well
Potentially reduce flocculation consumption
Promote mixing in the feed well
Increase throughput capacity
Redirect overflow to process water

Opportunities for improvement
More efficient froth spray design
Flocculation screening
Flocculation optimisation
De-aeration of slurry
Improve the feed box design
Area: Minning Maintenance Realibility
Thicker operation
Feed slurry becomes very diluted on entering the feed well and leaves the feed well as a dilute suspension from which particulate settling occurs.
A thickener has several basic components: a tank to contain the slurry, feed piping and a feed well to allow the feed stream to enter the tank, a rotating rake mechanism to assist in moving the concentrated solids to the withdrawal points, an underflow solids withdrawal system, and an overflow launder.
Area: Minning Maintenance Realibility
Conventional Thickeners
The conventional thickener can be used with or without flocculants, depending upon the application. If employed, flocculants are normally added to the feed launder or in the feed well, and flocculation occurs in the resulting turbulence.
Area: Minning Maintenance Realibility
High Rate Thickeners
High rate thickeners are designed specifically to maximise the flocculation efficiency of flocculants. They differ from conventional thickeners in feed well design, size and control.
Unlike conventional thickeners, high rate thickeners must use flocculants. The basic design of a high rate thickener is below. 
High rate thickener feed wells are designed to disperse flocculants thoroughly into the feed end to admit the flocculated slurry into the settling zone of the thickener without destruction of the newly formed floccules. The feed may enter into the sludge bed if the flocculation must be completed by the solids-contact means, or it may enter above the pulp level if it is sufficiently flocculated to produce the desired clarity and the underflow density.
The increase in flocculation efficiency realised in high rate thickeners may increase in a bulk settling rate 2 to 10 times over that obtained in a conventional thickener, thus reducing the unit area requirements by a similar factor.
The control parameters used to maintain stable operation in high rate thickeners are underflow solids density, underflow withdrawal rate, flocculant dosage, solids inventory in the tank, solids feed rate, and mechanical torque limit restriction of rotating rake arm mechanism.
Area: Minning Maintenance Realibility
Components and Accessories of Thickeners
A thickener consists of a collection of components, which can be supplied in a number of variations. The basic components are the same:
 Tank
 Drive Support Structure
 Drive Unit and Lifting Device
 Rake Structure
 Feed Well
 Overflow Arrangement
 Underflow Arrangement
 Instrumentation and Flocculation Facilities
Area: Minning Maintenance Realibility
Rake Lifting Mechanism
These should be provided when abnormal thickener operation is probable. Abnormal thickener operation or excessive torque may result from 
insufficient underflow pumping
surges in the solids feed rate
excessive amounts of large particles
sloughing of the solids accumulated between the rakes and the bottom of the tank or on structural members of the rake mechanism
Miscellaneous obstructions falling into the thickener. 

The lifting mechanism may be set to raise the rakes automatically when a specific torque level (eg 50% of design) is encountered, continuing to lift until the torque returns to normal or until the maximum lift height is reached.
Area: Minning Maintenance Realibility
Distributor Cone
The distributor cone is mounted directly below the feed well. The purpose of the distributor cone is to distribute flocculated slurry to the outside edge of the tank.
Area: Minning Maintenance Realibility
Overflow Arrangements
Clarified effluent typically is removed in a peripheral launder located inside or outside the tank. The effluent enters the launder by overflowing a 'V' notch or level flat weir. Uneven overflow rates caused by wind blowing across the liquid surface in large thickeners can be better controlled when 'V' notch weirs are used. The hydraulic capacity of a launder must be sufficient to prevent flooding, which can cause short-circuiting of the feed and deterioration of overflow density.
Area: Minning Maintenance Realibility
Underflow Arrangements
Concentrated solids are removed from the thickener by use of a centrifugal slurry pump, positive displacement pump or by gravity. The underflow arrangement must be designed to remove solids, without plugging upsets, at the maximum rate at which they will enter the thickener.
Provisions must be made to unplug or to bypass plugged piping so that solids can always be removed from the thickener to preclude their filling the thickener and stalling the mechanism. Underflow recycle back to the feed well is used in some applications to aid in flocculation of the unit during periods when the feed is reduced or interrupted. 
These are two basic under flow arrangements and are as follows:
 Tunnel
 Centre cone pumping (open area)
Area: Minning Maintenance Realibility
Instrumentation
Instrumentation is used on most thickeners to measure torque in order to prevent mechanical damage to the drive or rake mechanism by actuating a rake lifting device or shutting off power to the drive in the event of an overload. Some applications also require automatic control of thickener feed or discharge to maintain acceptable performance when departure from the norm occurs.
An approximately steady state material balance must be maintained around the thickener. Although the volume of pulp in the thickener can be allowed to increase or decrease within harmless limits, it must be controlled to prevent, on the one hand, solids from overflowing the thickener and, on the other hand, the bed pressure from falling so low that the underflow density drops below desired values. Variable pumping rates can be obtained by use of variable speed pumps or flow control valves. Underflow density measurements can be made by routine checks using a device like a Marcy pulp density scale by the operator or on line through use of a density gauge.
Area: Minning Maintenance Realibility
Thickener Operation Rules
INPUT minus OUTPUT equals ACCUMULATION.
Excessive accumulation results in operating problems, usually requiring shutdown and

If solids are allowed to accumulate in a thickener without corrective action, one or more of the following will occur:
 The pulp will begin to exit the tank with the overflow.
 The underflow will become too thick to pump.
 A 'doughnut' will form in the thickener and the underflow density will start to approach the feed density.
 The rake mechanism will become overloaded and be stopped by the drive control.
Automatic control on a conventional thickener is usually achieved by an underflow density loop that regulates the rate of withdrawal of underflow. A turbidity meter is sometimes used to measure overflow clarity and regulate the addition of a coagulant or polymer flocculants.
These measures are not adequate on a HRT; because they would not give optimum control and could lead to excessive flocculant use.
Area: Minning Maintenance Realibility
HRT Control Systems
Briefly a HRT operates in the following way (see Fig 1): feed enters the feed well which is designed to promote deaeration and floc formation. If the feed has a high solids concentration, it is usually necessary to add dilution water to allow effective floc formation.
Flocculant is injected into the feed and deaeration and flocculation occurs as the feed moves down the feed well. It leaves the feed well by impinging on the deflector cone, which imparts a horizontal velocity as it enters the body of the thickener.


Most HRT control systems are based on the regulation of underflow withdrawal rate to achieve control of bed level. Hence, when any of the above parameters change the underflow valve position is regulated to increase the underflow discharge if bed level rises and vice versa.
Area: Minning Maintenance Realibility
HRT Control System at Sunrise Dam Gold Mine
The control system installed in the SDGM thickener is shown in fig. 2 where the underflow density is controlled by a bed mass pressure probe and the flocculation rates controlled by a bed level probe. The control strategy based on bed mass is explained below.
Area: Minning Maintenance Realibility
Rittershaus & Blecher (R&B) pressure filters.


The Çayeli concentrator designed nameplate capacity was 600,000 tonnes per year. Originally, three Rittershaus & Blecher pressure filters were installed: one for copper concentrate, one for zinc concentrate, and one standby for both copper and zinc concentrates. Mill throughput gradually increased after commissioning and was 896,700 tonnes in 1999. At these production levels, the filtration capacity created a bottleneck. In 1999, CBI decided to increase the mill capacity to one million tonnes per year and a fourth filter was installed ?n the year 2000 as part of the expansion plan. A LASTA M.C. automatic filter press was selected.

These filters are high-maintenance items and required dedicated mechanics to look after them as production increased. Initially, one operator was budgeted for the dewatering section, but due to the operational difficulties of these filters, this was increased to two operators per shift. In choosing a filter, the main selection criteria were low maintenance and operation costs, and the filter had to be simple to operate and robust in design. The capacity requirement was 400 dmt/day.

The MC LASTA AUTOMATIC FILTER PRESS was selected. Industrial Process Machinery (IPM) offered a model MCFHC 1500 X 40/34 for 400 dmt/day operation. The number of plates offered was 34, while the frame capacity was 40 plates.
The auxiliaries were:
 one high pressure water pump for filter cloth washing, feed core clean-up, channel cleans, etc.,
 one slurry feed pump, which was also retrofit to the existing copper concentrate holding tank,
 one compressor, dedicated for use with the Lasta filter,
 one transfer pump, to pump filtrate and filter cloth washings.

The construction contract was awarded in mid-April and commissioning of the filter started in mid- August 2000. The filter was fully commissioned by the end of September 2000.
They programmed the PLC and checked that the filter operation was satisfactory.
Area: Minning Maintenance Realibility
Slurry Pumps
CENTRIFUGAL SLURRY PUMPS AND SLURRY PUMPING SYSTEMS
It is very common in these same plants to use pulley and belt drives between motors and pumps. The main reason for this is that duties often change  and mostly upwards  after initial installation. If the pump speed is not sufficient, it is then only a matter of changing one of the pulleys to get an increased speed, a higher throughput and, alas, also a higher power consumption. To cater for such power changes, it is strongly recommended to select the initial motors with sufficient reserve power, say some 10% to 20% above the initial calculated requirement. This extra power is also handy in correcting mistakes which invariably happen due to uncertainties in friction loss predictions, as mentioned above. A bigger motor is slightly more expensive but the confidence it generates is priceless.
Area: Minning Maintenance Realibility
PUMP SEALING
Associated with the impeller-throatbush seal face adjustment is the means of sealing the pump against leakage along the shaft. Most pumps still use the proven and versatile water-fed gland seal, which still provides the lowest sealing costs even though it requires reasonably frequent attention by the operators.
Most slurry pumps (and many clear liquid pumps) are designed with suction diameters larger than discharge diameters. The simple aim of this design modification is to reduce suction pipe velocity and consequent friction losses, which in turn increase available NPSH. This is particularly important in slurry pumping where the density of the slurry reduces the available NPSH.
Slurry pumps with powers up to about 300 kW are almost universally driven by fixed speed motors through sets of belts and pulleys to produce different pump speeds and generate various heads. Two reasons for selecting belt drives are their low cost and the ease of changing pump speeds.
A small but growing percentage of slurry pumps above 200 kW are also direct coupled to variable speed motors or to fixed speed motors via variable speed hydraulic couplings or variable frequency controllers.
Area: Minning Maintenance Realibility
PUMP SPEED AND WEAR
Whenever we are dealing with centrifugal pumps we are of necessity involved with flow rates, total heads, consumed power and pump speeds. The first three parameters are closely related to the forth,

This example comes from a copper mine. The specific gravity of copper ore is S=2.85, the flow of slurry fed to the cyclone is Q=61.7L/s, the solids concentration in the slurry is Cw=40% (and Cv=19%) and the specific gravity of the slurry is Sm=1.35.
Area: Minning Maintenance Realibility
WARMAN 10/8 T-AHPP gland sealed pumps.
Two trains of 7 stages. Tailings application. Rubber lined casings and high efficiency, hard-metal impellers.
Duty: Q=930 m3/h, Hm=55 m per stage, Cw=55%. Drives: 315 kW, 740 r/min motors, direct coupled.
Area: Minning Maintenance Realibility
ASH PUMP 22x20 SRH pumps.
Two trains of 3 stages (one train shown). Tailings application. Rubber lined casings and impellers.
Duty: Q=36005000 m3/h, Hm=2431 m per stage, Sm=1.21.3. Drives: 750 kW motors with gear reducers and Variable Frequency Speed Controllers.
Area: Minning Maintenance Realibility
WARMAN 20/18 TU-AH pumps.
One pump per processing circuit. Mill discharge application. Rubber lined casings, hard-metal impellers and throat bushes. Duty: Q=3200 m3/h, Hm=32.5 m, Cw=62%. Drives: 600 kW motors and gear reducers.