Interfacing in Crushing and Screening Plants

Interfacing in Crushing and Screening PlantsGROUP 2MANGLAM SHARDAANKU KUMAR PANDEYK .K .TEJAINTRODUCTIONA good crusher plant layout Crucial in meeting production demands Should keep capital and operational costs lowOperates at competitive cost Complies tough environmental regulations Economical to build

DESIGNING A CRUSHING PLANTThree main steps: process design, equipment selection, and layout.

The first two are dictated by production requirements and design parameters

The layout reflects the input, preferences and operational experience of a number of parties

Can include the owners engineering staff, safety personnel, operations and maintenance personnel, equipment manufacturers, and the engineering consultantDESIGN PARAMETERS Production requirements Capital cost Ore characteristics Project location Life of mine/expansion plans Operational considerations Maintenance requirementsPRODUCTION REQUIREMENTSThe process design criteria define the projects production requirements, and typically include:

CAPITAL COSTSEarthworks MechanicalConcreteElectricalStructural steel InstrumentationArchitectural

Construction indirectStart up and commissioningConstruction equipmentFreightSpare parts/first fill Taxes/dutiesEngineering, procurement and construction management (EPCM)Owners costs (relocation, hiring and training personnel, permits, licensing fees, etc)Direct CostsIndirect CostsORE CHARACTERISTICSCritical element in both crusher selection and plant design.

Dust suppression and collection, dust enclosures around screens, sealing on conveyor skirts, and vacuum and wash-down systems for dry ores

Wet, sticky ores can: Plug chutesReduce surge capacityDecrease the live storage capacity of bins and silos

Change over time, costly to design for optimal flexibility PROJECT LOCATIONTopography, geography and climatic conditions affect design

Construction costs greater at high altitudes, cold climates and remote sites

Modular and pre-assembled structures and plant facilities

Difficult to obtain spare parts on short notice

Provision for onsite repair and refurbishmentLIFE OF MINE/EXPANSIONKey elements in designShort term mine lives Require careful approach to design, layout and construction.Steel-supported, modular design

Large concrete structures with fully insulated enclosures for long term

Expansion better than recovery for increased production

Early planning stages better for expansion decision

OPERATIONAL CONSIDERATIONComfortable and well-ventilated workspacePotable water and toilet facilities nearby Direct visibility, TV, camera installation Quick and easy clean up in case of spills. Wash-down hoses within easy reach throughout the plantSufficient water pressure to wash down hard-to-access areasAdequate clearance above the conveyor floor to permit access to spillage by shovels or plowsWeight of replacement parts, which must be manhandled to be kept within 27 kg for ease of installation. Monorails and hoists to provide for ease of maintenance.

Maintenance RequirementsMinimum maintenance requirementsScheduled preventive maintenance:Crusher wear partsConveyor skirting and adjustmentOil and lubricationConveyor belt repairScreen decksFeeder wear partsOverhead cranes to remove and replace crusher wear partsSupports for gyratory and conveyor main shaftsCentralized oil and lubrication systemPROCESS DESIGN CRITERIATypically, the information required to develop crusher process design criteria includes:Geographic dataClimatic dataCivil design criteriaStructural design criteriaProcess design data (process description, ore characteristics)Mechanical design criteriaElectrical/instrumentation design criteria.

EQUIPMENT SELECTIONCrusher TypesDepends on the type and amount of material to be crushed

Gyratory and jaw crushers represent the bulk of primary crushers used at mining operations today

Cone crushers most popular for fine crushing applications

Some mines use vertical impact crushers for tertiary and quaternary crushingCONTDThe major equipment in a primary crushing circuit are crusher, feeder and conveyorSecondary and tertiary also include screens and surge storage binsOther equipment items in crushing circuits can include:

PRIMARY CRUSHER DESIGN

UPPER SUPERSTRUCTURECrane main hook speed should be slow, for inserting the main shaft.Always prepare a hook coverage plan to check all areas of crane service.Crane maintenance access should include stairs and a platform to service an overhead bridge crane.Choose the type of crane, overhead bridge, jib, gantry or mobile crane required to meet project requirements.A well-ventilated crusher control room is required.There must be a washroom, with or without potable water.The electrical room can be located at the upper or lower level; keep high-voltage runs short.The location of the dust collector should consider operating lengths of ductwork..Two main shaft supports are required, for the shaft in use and a spare.CRUSHER FLOOR LEVELA walkway platform around the crusher for easy spider removalA built-in circular monorail under the concrete to support for a trolley support air hammer used to remove or install the spider nutsCountershaft, in-line drive versus V-belt drive and clutch.The spider lube system should normally be located at the crusher floor level.The air-seal compressor can be located on the crusher floor.Balance cylinder located close to the crusher Maximum pipe bend radii for ease of quick response Provisions for oil relief collectionSURGE BIN AREAThe surge bin access door should be split horizontally on one side, to allow easy man access to one side without opening the whole door.For the crusher discharge opening, tapered concrete with a welded AR plate is preferred.Air cannon discharge points must be pre-designed. Locate the air receivers and valves out side the surge bin.Level detectors should be installed at high and low points in the surge pocket.For the eccentric trolley, a hung design is best, complete with a man-access platform at the top of trolley to permit servicing the crusher hydraulic cylinder and eccentric.Surge pocket withdrawal opening liners should be made in a minimum number of large pieces for ease of removal.CRUSHER LUBRICATIONThe crusher lubrication package must have maintenance access at all points.Crusher oil piping must consider protection and ease of maintenance. Lube piping routing is critical; correct slopes must be maintained as per the manufacturers recommendations.Automatic drain and re-supply piping must be provided.The crusher lube package must be in a well-ventilated area, and in a closed room ifpossible.Choose an automatic or manual system for crusher oil changes.Choose water- or air-cooling for the crusher lube system.ELECTRICAL CONSIDERATIONSThe electrical MCC/transformer electrical rooms can be located at the top or bottom of acrusher plant.Electrical cable tray routing and orientation should be checked by the mechanical process engineer. Vertical trays should be used to eliminate collection of spilled material in the trays.If the substation/electrical room is at the surface level, ensure there is no possibility of damage from impact from haul trucks.STRUCTURAL CONSIDERATIONSProvide easy stair access to each level.Provide access to both sides of the take-away conveyor.Braces and structures must be located away from equipment service and maintenanceareas.Primary crushing plant enclosure costs can represent up to two-thirds the capital cost of a crusher station. It is therefore very important to select the most economical structure for the support of the crusher and ancillary equipment. There are many approaches: total concrete structures, round concrete structures, a mixture of concrete and steel, and reinforced earth structures with steel levels. The designer should spend considerable effort on selecting a structure that best suits the design parameters outlined above.DUST COLLECTION/SUPPRESSIONThere are many choices for dust collection/suppression systems, including bag filters,scrubbers, cartridge collectors, surfactants, water sprays and sonic fog. Control, lube, compressor and electrical rooms should all be well-ventilated.Surge bins must include collection hoods.The take-away conveyor should have provisions for dust collection/suppression.Determine whether dust-collector air must be preheated in cold climates.A collector fan silencer should be considered, as fan noise can be excessive in closedareas.If an aircooling system is selected for crusher-oil, it will require venting for hot-air evacuation.