Introducing various metal casting defects with many pictures by Dandong Foundry in China. These are the common sand casting defects on the surface and inside of cast iron and cast steel parts. 1. Blowhole and Pinhole This is a kind of cavities defect, which is also divided into pinhole and subsurface blowhole. Pinhole is very tiny hole, some could be seen on the surface. Subsurface blowhole only can be seen after machining or grinding.
This defect includes chemical burn-on, and metal penetration. Normally, you could see extra metal materials at the corner positions. This is caused by the poor sand. The metal has penetrated into sand molds.
Sand hole is a type of typical shrinkage cavity defect. You could see the empty holes after sand blasting or machining process. The sand dropped from sand molds, rolling into the liquid metal, then caused sand holes.
It is also called as cold shut. It is a crack with round edges. Cold lap is because of low melting temperature or poor gating system. This is not just surface defect. Normally, this position may cause air leakage, moreover, the material quality at this position will be very poor, so may be fragile.
Joint flash is also called as casting fin, which is a thin projection out of surface of metal castings. Joint flash should be removed during cleaning and grinding process.
Sharp fins and burrs are similar problems as the flash. Actually, large flash is a casting problem, the foundry should improve it by modifying the patterns, but small fins and burrs are not casting defects, foundries just need to grind and remove them.
Shrinkage defects include dispersed shrinkage, micro-shrinkage and porosity. For large porosity on the surface, you could see them easily, but for small dispersed shrinkage, you may see them after machining. The following photo is showing the porosity shrinkage. The metal density is very poor, many small holes could be seen after machining.
These are also called as shrinkage holes, which is a type of serious shrinkage defect, you can see these holes easily on the rough surface of the metal castings. Foundries could improve their gating and venting system, then could solve these shrinkage problems.
This defect is also a type of shrinkage defect, which looks like depressed region on the surface of metal castings. This defect is not serious as shrinkage cavity, but still cause poor surface quality and may have some inside defects, so foundries should try their best to solve or improve it.
It is also called as rat tail, which looks like many small water flow traces on the surface of metal castings. Sometimes, it is because of the low metal temprature melted, or unreasonable gating and venting system.
This mold defect is because of the shifting molding flashes. It will cause the dislocation at the parting line. Near the parting line, the left side may be several milimeters lower or higher than another side. The parting line is not defect, but if the left side has different height as the right side, it will be one casting defect. If there is no special requirement, mismatch smaller than 1mm is allowable. No any mismatch is impossible for sand casting process.
This is not casting defect, but it is a real casting quality problem you may meet. It is the damage during machining or delivery processes. The workers should pay more attention to this problem.
This defect is also called as exogenous inclusion, entrapped slag. Normally, the slag is from melted metal. During metal melting process, foundries should remove the dirt and inclusion completely, otherwise, these inclusions will be poured into the castings.
This is also called as under-nodulizing defect. Because of many reasons, the spheroidization of graphite for ductile iron will be affected, therefore, caused the bad spheroidization rate. By metalloscope, you can see very few graphite balls, and many worm-like graphite.
It means the uneven hardness on the same surfaces. The hardness is not uniform, some postions may have extra high hardness. When machining to harder positions, the machining will become more difficult. The drill bit may be broken.
It is also called as sand crush. Some sand blocks dropped from the sand mold, so they will cause the similar shaped sand holes or incomplete. This is the problem of sand molds. The sand molds may not be tight enough.
This problem will cause the oversized tolerance for flatness and straightness. This is very common defect for long castings, and flat castings with thin wall thickness. The reasons are the natural deformation during cooling process in sand molds, or in air, sometimes, the overly sand blasting also could cause this problem.
After welding repair, even after machining or grinding, the welding marks will still be visual. As for unimportant casting surfaces, if the client allow welding repair, then these marks should be acceptable. But for high pressure-bearing positions, or the client has clearly forbidden any welding repair, then these marks will be taken as defects.
Chill iron could effectively reduce the shrinkage for the key positions, so using chill iron is very common in iron foundries. However, the edges of chill irons could be clearly found by visual inspection. Some clients will not require to grind them if these marks do not affect the appearance. However, the clients could require the casting manufacturer to grind them just for better surface looking. Please clearly notice that these marks should not be judged as the casting defects. Refer to iron-foundry.com.
It is also called as "white iron". The surface of the castings with this defect will be extremely white, shiny and smooth. The defective castings will be fragile and crispy, so during machining, some edges and tips will be broken. This defect was caused by the low temperature of sand molds, and prematurely out of sand molds, so the hot iron become chilled quickly. The proper annealing heat treatment to them could solve this defect.
On metallograph photo, you could see many fish-bone free carbide. This is a serious defect of cast iron material, normally happen to ductile iron. Because of inverse chilling defects and poor inoculation, there will be mass free carbide, which will cause fragile, poor welding property to ductile iron castings. High temperature annealing heat treatment could improve its quality.
This defect is also called as internal sweating. There are iron beans in the castings. This is because of unreasonable gating design, which caused some liquid iron became beans suddenly, then these beans were wrapped by other liquid irons. This is a surface defect, but will cause serous problem if they located in key positions.
There is very thin iron skin on the surface of castings. Two layers. This is because of unreasonable gating system, which caused very thin air layers existed. This defect is a surface defect, so normally it can be grinded off. However, it should be discarded if it is not just on the surface.
This defect is a kind of material problem. It is caused because of low pouring temperature and high content of carbon element. This defect is very harmful, will cause material very fragile. On the broken surface, you can see the obvious black surface caused by this defect.
LIAONING BORUI MACHINERY CO., LTD (DANDONG FOUNDRY) All Rights Reserved ADD: No.1-4-6, Jianshe Road, Qianyang Town, Donggang, Dandong, Liaoning, China 118301 SITEMAP| China Foundry
Silica sand low in iron is much in demand for glass, ceramic and pottery use, and for many of these applications clean, white sand is desired. Impurities such as clay slime, iron stain, and heavy minerals including iron oxides, garnet, chromite, zircon, and other accessory minerals must not be present. Chromium, for example, must not be present, even in extremely small amounts, in order for the sand to be acceptable to certain markets. Feldspars and mica are also objectionable. Generally, iron content must be reduced to 0.030% Fe2O3 or less.
Silica sand for making glass, pottery and ceramics must meet rigid specifications and generally standard washing schemes are inadequate for meeting these requirements. Sand for the glass industry must contain not more than 0.03% Fe2O3. Concentrating tables will remove free iron particles but iron stained and middling particles escape gravity methods. Flotation has been very successfully applied in the industry for making very low iron glass sand suitable even for optical requirements.Sub-A Flotation Machines are extensively used in this industry for they give the selectivity desired and are constructed to withstand the corrosive pulp conditions normally encountered (acid circuits) and also the abrasive action of the coarse, granular, slime free washed sand.
The flowsheet illustrates the more common methods of sand beneficiation. Silica may be obtained from sandstone, dry sand deposits and wet sand deposits. Special materials handling methods are applicable in each case.
The silica bearing sandstone must be mined or quarried much in the manner for handling hard rock. The mined ore is reduced by a Jaw Crusher to about 1 size for the average small tonnage operation. For larger scale operations two-stage crushing is advisable.
The crushed ore is reduced to natural sand grain size by Rod Milling. Generally, one pass treatment through the Rod Mill is sufficient. Grinding is done wet at dilutions in excess of normal grinding practice. A Spiral Screen fitted to the mill discharge removes the plus 20 mesh oversize which either goes to waste or is conveyed back to the mill feed for retreatment.
Sand from such deposits is generally loaded into trucks and transported dry to the mill receiving bin. It is then fed on to a vibrating screen with sufficient water to wash the sand through the 20 mesh stainless screen cloth. Water sprays further wash the oversize which goes to waste or for other use. The minus 20 mesh is the product going to further treatment.
The sand and water slurry for one of the three fore-mentioned methods is classified or dewatered. This may be conveniently done by cyclones or by mechanical dewatering classifiers such as the drag, screw, or rake classifiers.
From classification the sand, at 70 to 75% solids, is introduced into a Attrition Scrubber for removal of surface stain from the sand grains. This is done by actual rubbing of the wet sand grains, one against another, in an intensely agitated high density pulp. Most of the work is done among the sand grains not against the rotating propellers.
For this service rubber covered turbine type propellers of special design and pitch are used. Peripheral speed is relatively low, but it is necessary to introduce sufficient power to keep the entire mass in violent movement without any lost motion or splash. The degree of surface filming and iron oxide stain will determine the retention time required in the Scrubber.
The scrubbed sand from the Attrition Machine is diluted with water to 25-30% solids and pumped to a second set of cyclones for further desliming and removal of slimes released in the scrubber. In some cases the sand at this point is down to the required iron oxide specifications by scrubbing only. In this case, the cyclone or classifier sand product becomes final product.
Deslimed sand containing mica, feldspar, and iron bearing heavy minerals can be successfully cleaned to specifications by Sub-A Flotation. Generally this is done in an acid pulp circuit. Conditioning with H2SO4 and iron promoting reagents is most effective at high density, 70-75% solids. To minimize conditioning and assure proper reagentizing a two-stage Heavy Duty Open Conditioner with Rubber Covered Turbine Propellers is used. This unit has two tanks and mechanisms driven from one motor.
The conditioned pulp is diluted with water to 25-30% solids and fed to a Sub-A Flotation Machine especially designed for handling the abrasive, slime free sand. Acid proof construction in most cases is necessary as the pulps may be corrosive from the presence of sulfuric acid. A pH of 2.5-3.0 is common. Wood construction with molded rubber and 304 or 316 stainless steel are the usual materials of construction. In the flotation step the impurity minerals are floated off in a froth product which is diverted to waste. The clean, contaminent-free silica sand discharges from the end of the machine.
The flotation tailing product at 25 to 30% solids contains the clean silica sand. A SRL Pump delivers it to a Dewatering Classifier for final dewatering. A mechanical classifier is generally preferable for this step as the sand can be dewatered down to 15 to 20% moisture content for belt conveying to stock pile or drainage bins. In some cases the sand is pumped directly to drainage bins but in such cases it would be preferable to place a cyclone in the circuit to eliminate the bulk of the water. Sand filters of top feed or horizontal pan design may also be used for more complete water removal on a continuous basis.
Dry grinding to minus 100 or minus 200 mesh is done in Mills with silica or ceramic lining and using flint pebbles or high density ceramic or porcelain balls. This avoids any iron contamination from the grinding media.
In some cases it may be necessary to place high intensity magnetic separators in the circuit ahead of the grinding mill to remove last traces of iron which may escape removal in the wet treatment scrubbing and flotation steps. Iron scale and foreign iron particles are also removed by the magnetic separator.
In general most silica sands can be beneficiated to acceptable specifications by the flowsheet illustrated. Reagent cost for flotation is low, being in the order of 5 to 10 cents per ton of sand treated. If feldspars and mica must also be removed, reagent costs may approach a maximum of 50 cents per ton.
Laboratory test work is advisable to determine the exact treatment steps necessary. Often, attrition scrubbing and desliming will produce very low iron silica sand suitable for the glass trade. Complete batch and pilot plant test facilities are available to test your sand and determine the exact size of equipment required and the most economical reagent combinations.
Silica sand for making glass, pottery and ceramics must meet rigid specifications and generally standard washing schemes are inadequate for meeting these requirements. Sand for the glass industry must contain not more than 0.03% Fe2O3. Concentrating tables will remove free iron particles but iron stained and middling particles escape gravity methods. Flotation has been very successfully applied in the industry for making very low iron glass sand suitable even for optical requirements.
Sub-A Flotation Machines are extensively used in this industry for they give the selectivity desired and are constructed to withstand the corrosive pulp conditions normally encountered (acid circuits) and also the abrasive action of the coarse, granular, slime free washed sand.
The flowsheet illustrated is typical for production of glasssand by flotation. Generally large tonnages are treated, forexample, 30 to 60 tons per hour. Most sand deposits can be handled by means of a dredge and the sand pumped to the treatment plant. Sandstone deposits are also being treated and may require elaborate mining methods, aerial tramways, crushers, and wet grinding. Rod Mills with grate discharges serve for wet grinding to reduce the crushed sandstone to the particle size before the sand grains were cementedtogether in the deposit. Rod milling is replacing the older conventional grinding systems such as edge runner wet mills or Chilean type mills.
Silica sand pumped from the pit is passed over a screen, either stationary, revolving or vibrating type, to remove tramp oversize. The screen undersize is washed and dewatered generally in a spiral type classifier. Sometimes cone, centrifugal and rake type classifiers may also be used for this service. To clean the sand grains it may be necessary to thoroughly scrub the sand in a heavy-duty sand scrubber similar to the Heavy-duty Agitator used for foundry sand scrubbing. This unit is placed ahead of the washing and dewatering step when required. The overflow from the classifier containing the excess water and slimes is considered a waste product. Thickening of the wastes for water reclamation and tailings disposal in some areas may be necessary.
The washed and dewatered sand from the spiral-type classifier is conveyed to a storage bin ahead of the flotation section. It is very important to provide a steady feed to flotation as dilution, reagents and time control determines the efficiency of the process.
Feeding wet sand out of a storage bin at a uniform rate presents a materials handling problem. In some cases the sand can be uniformly fed by means of a belt or vibrating-type feeder. Vibrators on the storage bin may also be necessary to insure uniform movement of the sand to the feeder. In some cases the wet sand is removed from the bin by hydraulic means and pumped to a spiral-type classifier for further dewatering before being conveyed to the next step in the flowsheet.
Conditioning of the sand with reagents is the most critical step in the process. Generally, for greater efficiency, it is necessary to condition at maximum density. It is for this reason the sand must be delivered to the agitators or conditioners with a minimum amount of moisture. High density conditioning at 70 to 75% solids is usually necessary for efficient reagentizing of the impurity minerals so they will float readily when introduced into the flotation machine.
The Heavy-duty Duplex Open-type Conditioner previously developed for phosphate, feldspar, ilmenite, and other non-metallic mineral flotation is ideal for this application. A duplex unit is necessary to provide the proper contact time. Circular wood tanks are used to withstand the acid pulp conditions and the conditioner shafts and propellers are rubber covered for both the abrasive and corrosive action of the sand and reagents.
Reagents are added to the conditioners, part to the first and the balance to the second tank of the duplex unit, generally for flotation of impurities from silica sand. These reagents are fuel oil, sulphuric acid, pine oil, and a petroleum sulfonate. This is on the basis that the impurities are primarily oxides. If iron is present in sulphide form, then a xanthate reagent is necessary to properly activate and float it. The pulp is usually regulated with sulfuric acid to give a pH of 2.5-3.0 for best results through flotation.
A low reagent cost is necessary because of the low value of the clean sand product. It is also necessary to select a combination of reagents which will float a minimum amount of sand in the impurity product. It is desirable to keep the weight recovery in the clean sand product over 95%. Fatty acid reagents and some of the amines have a tendency to float too much of the sand along with the impurities and are therefore usually avoided.
After proper reagentizing at 70 to 75% solids the pulp is diluted to 25 to 30% solids and introduced into the flotation machine for removal of impurities in the froth product. Thepulp is acid, pH 2 .5 to 3.0 and the sand, being granular and slime free, is rapid settling so a definite handling problem is encountered through flotation.
The Sub-A Flotation Machine has been very successful for silica sand flotation because it will efficiently handle the fast settling sand and move it along from cell to cell positively. Aeration, agitation and selectivity due to the quiet upper zone can be carefully regulated to produce the desired separation. The machine is constructed with a wood tank and molded rubber wearing parts to withstand the corrosive action of the acid pulp. Molded rubber conical-type impellers are preferred for this service when handling a coarse, granular, abrasive sand.
Flotation contact time for removal of impurities is usually short. A 4, and preferably a 6 cell, machine is advisable. Cell to cell pulp level control is also desirable. A 6 cell No. 24 (43 x 43) Sub-A Flotation Machine in most cases is adequate for handling 25 to 30 tons of sand per hour. If the impurities are in sulphide form a standard machine with steel tank and molded rubber parts is adequate provided the pulp is not acid. Otherwise acid proof construction is essential.
The flotation tailing product is the clean sand discharging from the end of the flotation machine at 25 to 30% solids and must be dewatered before further processing. Dewatering can be accomplished in a dewatering classifier and then sent to storage or drying. Top feed or horizontal vacuum filters are often used to remove moisture ahead of the dryer. Dry grinding of the sand to meet market requirements for ceramic and pottery use is also a part of the flowsheet in certain cases.
This particular sand was all minus 20 mesh with only a trace minus 200 mesh and 70% plus 65 mesh. Iron impurity was present as oxide and stained silica grains. The plant which was installed as a result of this test work is consistently making over a 95% weight recovery and a product with not over 0.02% Fe2O3 which at times goes as low as 0.01% Fe2O3.
Si02, minimum..99.8 per cent Al2O3, maximum..0.1 percent Fe2O3, maximum..0.02 per cent CaO + MgO, maximum.0.1 percent For certain markets, a maximum of 0.030 per cent Fe2O3 is acceptable.
Natural silica-sand deposits generally contain impurityminerals such as clay, mica, and iron oxide and heavy iron minerals which are not sufficiently removed by washing and gravity concentration. Flotation is often used to remove these impurity minerals to meet market specifications.
Anionic-type reagents, such as fatty acids, are used to float some impurities in alkaline pulp. Cationic-type reagents such as amines or amine acetates are also used with inhibitors such as sulphuric or hydrofluoric acids to float certain impurity minerals and depress the silica.
Raw water enters near the bottom of the tank by means of a stainless steel water distributor. Suspended solids are filtered out as the raw water flows up through the media bed. As the filtrate reaches the top of the filter, it passes over the effluent weir and is discharged. A portion of the filtrate is diverted through the sand washer and used for cleaning and transferring the waste solids.
The SuperSand filter employs a backwash rinse that is performed continually while the tank is processing water. An air lift pump, located at the center of the module, draws the media from the bottom of the filter up into the wash box. As the media is released into the wash box, it falls into the sand scrubber where the filtered solids are separated from the sand. From there, the filtrate carries the solids out as waste (backwash). The washed sand falls down onto the media bed for continued use.
Whether you need reuse quality water, nutrient removal, industrial water treatment, or raw water treatment, WesTechs SuperSand delivers unmatched effluent quality, meeting the highest of environmental standards.
The filter cells (each consisting of multiple filter modules) share a common sand bed. A plant can be designed for a virtually unlimited filter area, enabling the SuperSand to be applied to small and large treatment plants with capacities ranging from 0.05 MGD to flow rates in excess of 100 MGD.
McLanahan Sand Washing Plants process sand from its raw state into products that meet various specifications. The process requirements vary depending on the input and desired output, but plants typically scrub, liberate, deslime, wash, classify, decontaminate and dewater the sand, as well as process the effluent stream that results.
For customers who are interested in maximizing yield and producing precisely graded products to the end-user's needs and specifications, it is more likely that a custom sand plant is the correct solution. Whether the sands are natural or manufactured, fine or coarse, well or poorly graded, or required for specialty applications, McLanahan can offer a plant specifically designed to suit your needs.
McLanahan is best known for creating process solutions to address the specific needs of each customer's application. We have one of the largest ranges of robust, field-proven equipment, and we are constantly innovating. Our background and expertise in applications is second to none.
Depending on the application, McLanahan can perform lab scale tests on materials, including sieve analysis, percent solids, attrition scrubbing, sink/float, sand equivalency and durability, Hydrosizer based classification, static and dynamic flocculation/settling and Filter Press testing.
With our proprietary simulations, in-house lab and industry expertise, you get a plant designed specifically for your site with capacities to match your need. Our expertise is the envy of the industry, so when you couple this with one of the largest ranges of equipment offerings, we can offer a solution.
Sand Washing comes in many forms and covers a range of feed and products produced, including construction aggregates such as concrete, asphalt, mason, mortar, and plaster sands; sports sands such as for golf courses, ball parks, and race courses; industrial sands, such as glass, filter, foundry, and frac; specialty sands and materials such as anti-skid, roofing granules; deligniting/organics removal; and soils washing for environmental projects.
First, consider the following questions: What do you have? What do you want to make? If the answer is a very specialized gradation and a difficult natural sand deposit, then consider a Recipe Plant. If the answer is a manufactured sand and you are making concrete sand all day every day, then an Ultra Sand Plant or Modular Wash Plant may be your answer.
Many other factors, such as available investment, local competition and expanding markets, will influence this decision. Through a process of elimination starting with the simplest configuration, McLanahans experienced personnel will guide you through to the best options.
Ultra Sand Plants, which utilize Dewatering Screens, Pumps and Cyclones, offer greater separation efficiency and provide a higher product yield that can be reused almost immediately due to the effectiveness of the Dewatering Screen. Ultra Sand Plants are commonly used to wash and dewater industrial and specialty sands, as well as asphalt, concrete and masonry sands.
For high-quality sand that meets strict specifications, look no further than McLanahan Recipe Sand Plants. These sand plants make use of every grain of sand to offer customized blending for concrete, foundry, glass and plaster sands. The resulting sand product is consistent, uniform and will meet even the tightest of specifications.
McLanahan In-Line Blending Sand Plants provide high product yields, offer flexible blending options, produce drier products and improve product consistency. They are simple to operate, create accurate splits and are field-proven.
McLanahan designs each of its Frac Sand Plants to meet the specific needs of each customer. Using field-proven McLanahan equipment, Frac Sand Plants can be designed for classifying, desliming, dewatering, pumping, scrubbing, sizing, tailings management and waste solids management. McLanahan Frac Sand Plants are engineered to make the critical separations required for frac sand. They produce the highest product yield at the lowest moisture.
Classifying Tank Based Sand Plants can create multiple products from a single feed as well as remove slimes and excess water. Feed material enters the Sand Classifying Tank first, and sand grains settle in sections according to size down the length of the tank. Valves at the bottom of each section release the grains into one of several flumes used to create a primary, secondary or tertiary product, depending on the application. The discharged products are then dewatered by Dewatering Screens and/or Fine Material Screw Washers. The addition of Cyclones and/or rising current water can be used to deslime the feed.
McLanahan Industrial Sand Plants are designed with a combination of McLanahan equipment to provide extremely sharp classification of various industrial sands. This equipment can include Attrition Cells, Dewatering Screens, Hydrocyclones, Hydrosizers, Filter Presses, Fine Material Screw Washers, Pumps, Separators and Thickeners.
Although Portable Plants, which can be wheel-mounted or skid-based to provide an ease of transport, are limited in capacity, they do not limit the process. Portable Sand Plants can be used for classifying, dewatering, sizing and removing oversize and organics from feeds to produce aggregates, construction and demolition materials, and specialty sands.
McLanahan Ultra Fines Recovery Plants can recover +400 mesh material for use in many industries. UFRs are especially well-suited in the aggregates industry for effluent streams containing <100 mesh fractions and for recovering valuable coal from effluent streams in the coal industry.
Fine Material Screw Washers wash, classify and dewater -10mm or 3/8 solids material in one machine. They often accept feed slurry from Wash Screens, Sand Classifying Tanks, Hydrocyclones, Hydrosizers and other Fine Material Screw Washers. If an application calls for a greater level of dewatering, they are often placed in series with a Dewatering Screen.
Fine Material Screw Washers are especially simple for operations looking to wash dry screened fines. When compared to other sand washing systems, Screw Washers are a low-capital cost and low electric power user machine. They are widely used by construction sand producers, mining companies, solar salt/brine processors and glass recycling plants.
McLanahan offers an extensive range of sizes of Fine Material Screw Washers. Sizing and selection is based on several factors, including the type of feed solids, feed gradation, desired product specification, capacity required and volume of the feed slurry. It is extremely important that all of these factors are taken into consideration when selecting the proper size of screw washer. Poor design and planning can lead to overflow of desired fine material, resulting in lost product and profit. McLanahan Corporations utilizes its vast experience in washing and classifying equipment to ensure proper machine size by reviewing application data that includes slurry volume and your feed gradation data of water coming in with the feed.
Sometimes when processing a very dilute sand slurry, such as at a stone rinsing vibrating screen station, and needing to retain +200 mesh or 75 micron solids, a sand screw size selection may need to be larger than what appears to be required when the solids feed rate isnt that much. If you look at a manufacturers tons per hour data, a machines water volume capacity may not meet your needs for fine sand solids retention based on the water volume capacity chart.
McLanahan Corporation offers a wider range of Fine Material Sand Screws than other manufacturers. High Water Volume Screw Washers are available sizes that allow the mixing and matching of a screw shaft size to handle a reduced capacity of sand solids with a washer box tub to handle a larger than normal water volume. This provides a lower cost option as compared to a larger standard sand screw. If the sand capacity is 50 tph with 1,000 gallons per minute of water, a 36 diameter screw shaft can be provided in a 54 washer box tub.
High Water Volume Screw Washers have been in operation since 2002, providing operators a proper alternative with increased product sized sand fines retention, as opposed to a standard machine selected incorrectly for just the tons per hour sand solids capacity.
To achieve the desired results with a Fine Material Screw Washer, sand or other fine material is directed to the feed box in the baffle plate. Coarse, heavier materials settle to the bottom of the box, while ultra-fine waste fractions are carried by the up-current of water to the surface and overflow the weirs.
Heavier material that settles to the bottom is conveyed up an 18-degree slope toward the discharge end. The rolling and tumbling of the material releases fines and some lightweight fractions into suspension. It also mildly scrubs superficial clays from the sand/mineral surfaces. As the material is conveyed toward the discharge end, the water begins to separate from the material. A channel in the washer box/tub is provided opposite the conveying side to allow water to drain from the solids and overflow the weirs.
In order to properly retain material in a screw washer, a calm pool area must be maintained. The feed box within the baffle plate is used to direct material away from the calm pool area; however, if the pool area is turbulent, finer material that may be desirable in the final product will overflow the weirs. The baffle plate helps to separate the washer box feed area and keep the pool area calm. In some applications, producers may remove the baffle plate and feed the material close to the back plate of the weir to help agitate the pool area and overflow undesirable material.
The speed of the Fine Material Screw Washer is determined by the percent passing 50 mesh in the desired product. If the screw washer is running too fast, material does not have a chance to stay on the flight long enough to dewater. The material will fall off of the flight and return to the pool area, leading the box to eventually fill with sand and stall the screw shaft.
Fine Material Screw Washers are widely used to wash and dewater: alluvial/natural sands, manufactured/crushed sands, frac sands, industrial/silica sands, iron ore fines, fine phosphate solids, solar evaporated salt solids and crushed glass.
Hydrocyclones, Dewatering Screen systems using a Hydrocyclone, and bucket wheels. Youll find that for the cost and low kW (hp) requirements, a Fine Material Screw Washer will be an extremely viable option and a good choice for you.
Functioning to wash, dewater and classify all solids material all in one machine, McLanahan Fine Material Screw Washers are ideal for construction sand producers, mining companies, salt/brine reclamation and glass recycling. Fine Material Screw Washers create a drier product discharge, while preventing water and even the smallest particles from reaching the bearing thanks to the McLanahan Twin-Seal Pak submerged rear bearings.