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Description On Performance Of Ore Crushers

Power generation industry studies have shown that ore crushers are an area where improved equipment reliability is badly needed.The electric research institute (epri) has determined that 1% of plant availability is lost on average due to crusher related problems.Epri also identified oil contamination and excessive leakage as two areas where jaw crusher drive train failures account for 53% of crusher problems.Description pulverization is currently the favored method of preparing ore for burning.Mechanically pulverizing ore into a fine powder enables it to be burned like a gas, thus allowing more efficient combustion.Transported by an air or an air/gas mixture, pulverized ore can be introduced directly into the boiler for combustion.There are several pieces of equipment involved in processing ore to be burned in this fashion.Combustion engineering, babcock & wilcox, and riley stoker corp.Are major manufacturers of ore pulverizing equipment.The four most common types of ore crushers are: ball mills this type of mill consists of a rotating tube filled with cast alloy balls.Ore is introduced through two hollow trunnions on each side of the tube.As the tube rotates, the balls tumble onto the ore, crushing and pulverizing it.Impact mills grinding action is carried out by a series of hinged or fixed hammers revolving in an enclosed chamber with wear resistant plates.The hammers impact on the ore, crushing it against the plates.Further pulverization is achieved as the smaller ore particles are ground through attrition against each other and the grinding face.Vertical roller mills this mill uses hydraulically loaded vertical rollers resembling large tires to pulverize raw ore fed down onto a rotating table.As the table rotates, the raw ore is pulverized as it passes underneath the rollers.Hot air forced through the bottom of the pulverizing chamber removes unwanted moisture and transports the pulverized ore dust up through the top of the crusher and out the exhaust pipes directly to the burner.The more recent ore crusher designs are vertical roller mills.Ring-roll and ball-race mills a ball mill or roller between two races or rings provides the grinding surfaces on which pulverization occurs.One or both of the races may rotate against a ball or roll (in a ring-roll mill the rolls may rotate while the ring is stationary).Ring-roll (bowl-mill) and ball-race mills comprise the majority of ore crushers currently in service at power generating facilities.Raw ore enters the top of the crusher through the raw ore feed pipe.The raw ore is then pulverized between the roll and rotating ring.Hot air is forced in through the bottom of the pulverizing chamber to remove unwanted moisture and transport the ore dust up through the top of the crusher and out the exhaust pipe directly to the burner.Ore that has not been pulverized into fine enough particles cannot be blown out of the top of the unit; it falls back to the ring and roll to be further pulverized.Contamination ingression the gears and bearings in the gearbox are oil lubricated.Fine ore particles and wear metals from grinding surfaces enter the lube oil through worn bearing and shaft seals, as well as being "inhaled" through reservoir vents.Historically, the design of crushers has been based on the expectation of few drive system problems under prescribed operation and maintenance.In practice, this has often been found not to be true.Oem supplied filtration many ore crusher designs do not incorporate any filtration in their lube circuits.The crushers that do not incorporate filtration use coarse filtration such as 40-micron cleanable mesh or 200-micron cleanable, stacked disk filters.Such oem-supplied filtration is often unable to keep up with the inherently high ingression rate.This results in contamination levels often exceeding iso code 30/30, particularly on older designs.This high level of contamination can severely diminish bearing, gear, pump, and seal life, leading to premature need for replacement or rework.Ore crusher downtime can be a major factor in reducing overall plant availability and reliability.

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