Is Your Maintenance Team Prepared?
Protect your big ticket equipment with a properly trained and educated team of maintenance personnel.
Many aggregate producers will experience decreased profit margins because their maintenance team does not fully understand the maintenance requirements and operational parameters of the equipment with which they work. Are you one of these producers?
Cost-effective maintenance and operations techniques begin with workers who are knowledgeable about the equipment to which they are assigned. In the real world, however, the level of equipment knowledge demonstrated by many aggregate-producing plant employees is far too often found to be inadequate.
Equipment that is maintained and operated by personnel who are not properly trained will eventually suffer from escalating operating costs due to poor disassembly/assembly practices, preventive maintenance neglect, premature component wear, frequent equipment overloads, erratic use of connected horsepower, and similar faults.
Some aggregate producers make enough profit each year to offset the cost of continued and unnecessary replacement of equipment parts and lost revenue associated with equipment downtime. At best, such organizations are earning less profit then they might otherwise enjoy. At worst, they are headed for financial trouble because declining profit margins and increased competition will catch up with them.
I’ve always said that insanity consists of continually making the same repairs but expecting different results. Yet, far too many aggregate producers get caught up in this trap. Problems related to inadequate personnel training exist at nearly every aggregate production plant, regardless of size.
One of the most frustrating statements an equipment manufacturer’s field representative can hear from a customer is, “We’ve been running this crusher for “X” number of years, and we know it better then you do.”
Most factory technical representatives are diplomatic enough to ignore such comments. However, statements such as this reflect an attitude that leads to equipment neglect. Maintenance personnel who think they know everything about a certain type of equipment often create or cause unnecessary problems.
One widespread example of dangerous misinformation is a belief, held by many veteran aggregate employees, that higher lubricating oil pressure is good for some cone crushers. There have been many cases of responsible plant maintenance personnel who have taken the factory-supplied main relief valve off their cone crusher and replaced it with a main relief valve with a higher-pressure rating. The purpose of such a modification is to permit the crusher to operate at a higher lubricating oil pressure level. For reasons that are not completely clear, these employees have decided to “modify” the manufacturer’s lubrication system.
Unfortunately, such modifications can and usually will cause serious damage, or possibly even a catastrophic failure of the crusher. A cone crusher is designed to operate with countershaft box oil pressure within a particular range. For example, the Symons Cone Crusher is designed to operate at 5 to 10 psi for the 3-, 4- and 4 1/4-foot model sizes or at 5 to 15 psi for the 5 1/2- and 7-foot model sizes.
Operating a cone crusher with excessive oil pressure will cause the eccentric assembly to hydraulic (lift) during operation. This leads to decreased bearing clearance between the taper of the main shaft and the taper of the inner eccentric bushing and a mismatch (disengagement) of the gear teeth in relationship to the pinion teeth. The reduction in bearing clearance will create excessive oil temperature and can result in a burnt inner eccentric bushing, a burnt main shaft, or a broken main shaft. The mismatch of the gear and pinion teeth can lead to broken teeth.
The main relief valve limits the amount of oil pressure that can enter the crusher. The main relief valve setting is 10 psi for the 3-, 4- and 4 1/4-foot model sizes or 15 psi for the 5 1/2- and 7-foot model sizes.
A manufacturer’s design engineers establish the correct oil pressure range and main relief valve settings. This is done after careful calculations, prototype testing, and long-term field experience. The operation of the lubrication system, as designed by the manufacturer, is essential to assure proper lubrication and cooling of the cone crusher.
When operating personnel make modifications that alter the intended operation, such as installing a main relief valve of a higher pressure rating, they actually defeat the purpose of the lubrication system. The inevitable result is continuous overheating and premature failure of internal components (see Figure 1). This kind of modification is an extreme example, yet it is fairly common.