Introduction
As with any type of processing equipment, maintenance is key to ensuring longevity and optimal performance of Sizers.
Sizers are direct-drive crushing machines that incorporate two rotating breaker shafts. The primary function of these machines is to crush or size material to the required product size to suit downstream handling and preparation plant processes. Sizers can be used in primary, secondary, tertiary, fine-grinding and low-tonnage applications and can process a variety of materials, such as copper, gold, iron ore, nickel, coal and more.
To ensure the best operation and lifespan of your Sizer, establish and follow a preventative maintenance schedule. This maintenance strategy should be determined based on the needs of each specific site, using the maintenance guidelines in the Sizer’s manual as the baseline for the minimum requirements. Depending on the site and application, some of the recommended inspections and checks may need to be performed more frequently.
Keep in mind that the first rule of any successful preventative maintenance program is safety. Prior to maintaining any parts of a Sizer, be sure to recognize and follow all machine safety tags, appropriate lock out/tag out/block out procedures and all site-specific safety requirements.
The second rule is consistency. Once you have developed a maintenance plan, be sure to follow it to a T.
The following is an example of recommended maintenance activities for Sizers. Keep in mind that the list is not exhaustive and should only be used as a guide for you to create your own specific maintenance plans.
Lubrication
Lubrication is vital for continual trouble-free operation. Many component failures are directly traceable to factors such as contaminated lubricant, improper lubricant, improper lubricant quantity and incorrect lubrication frequencies. These failures are often preventable through good housekeeping and proper lubrication practices, such as:
- Sealing all grease and oil storage containers to prevent dust, grit and moisture contamination
- Thoroughly cleaning all grease and oil lines before installation
- Wiping all fittings with a clean rag before lubricating to prevent forcing contaminants into the component
- Establishing a regular lubrication schedule and follow it faithfully
- Providing sufficient safeguards to prevent a loss of lubricant to the machine and include a regular visual inspection of the equipment, regardless of the number of mechanical safeguards provided
Some other tips to keep in mind regarding lubrication:
- Electric motor bearings should not be over-greased and are not connected to the lubrication system
- Consult your local lubricant supplier for any special conditions, such as extreme ambient temperatures
- Know the volume per stroke of your grease gun to appropriately lubricate the components – if this is unknown, it can be determined by pumping grease into a small container of known volume and counting the number of strokes required to fill the container
- Know which components require manual lubrication
Daily maintenance (once per 12-hour shift)
- Test all emergency stop switches
- Inspect the machine for loose/missing covers or guards
- Inspect all bearings for excessive heat
- Inspect the reducers for oil leaks, excessive heat and excessive noise
- Inspect fluid coupling for oil leaks, excessive heat, excessive noise and loose parts
- Inspect the motors for excessive heat and excessive noise
- Inspect all lubrication and hydraulic hoses and fittings for leaks and damage
- Inspect all instrumentation, electrical cables and connections for damage
- Inspect the speed monitoring sensors for damage and verify correct operation
Weekly maintenance (140 working hours)
- Inspect all bearing housing fasteners for tightness
- Inspect all reducer, bell housing and motor fasteners for tightness
- Clean electric motor cooling fins and fans
- Clean bell housing air vents
- Clean gear reducer housing
- Check desiccant breathers and replace as required
- Listen for abnormal noises on breaker shaft drives, automatic lubrication unit and hydraulic power unit (HPU)
- If your Sizer is equipped with an oil conditioning system, wipe down surfaces of the oil conditioner
- Inspect all components of the HPU for leaks and damage, including the reservoir, hoses and cylinders
Monthly maintenance (600 working hours)
- Inspect the breaker shafts and breaker bar for wear, damage and loose, damaged or missing teeth
- Inspect the breaker shafts, breaker bar and liner scrapers for lodged material
- Inspect liners for wear and inspect for missing liners
- Inspect crushing segment fasteners and check for correct bolt tension
- Inspect breaker bar fasteners and check for correct bolt tension
- Wipe down the HPU, and clean internal surfaces of oils or dust
- If your Sizer has an automatic lubrication system, inspect components and internals of cabinet for leaks, and wipe down and clean internal surfaces of excess grease and dust
Quarterly maintenance (1,800 working hours)
- Inspect all fasteners for tightness, including wear plates and covers
- Sample reducer gear oil and test for contaminants and oil breakdown
- Inspect fluid coupling flexible element backlash and axial alignment
- Inspect lifting lugs for damage and corrosion
Semi-annually maintenance (3,600 working hours)
- Inspect gear coupling teeth for damage and corrosion
- If your Sizer is equipped with an oil conditioning system, wipe down surfaces of the oil conditioner
- If your Sizer has an automatic lubrication system, clean or replace the pump outlet filter
Annually maintenance (7,200 working hours)
- Complete structural audit of the machine frame
- Inspect all hydraulic cylinder rods for corrosion
- Inspect machine frame for corrosion and damaged protective coatings
- Inspect exposed metal surfaces in shafts or drive components for corrosion
- Replace hydraulic oil in the HPU
- If your Sizer has an automatic lubrication system, clean or replace the grease fill filter
Tips for tramming drives
Some Sizers are equipped with tramming drives that allow them to roll out of the operational position via rails built into the support structure into an easily accessible maintenance position. Keep these tips in mind before and during tramming:
Prior to tramming:
- Remove dust and dirt from the gear unit casings and motor fan cowl, but do not use solvents or direct high pressure water jets at the gear unit
- Check for lubricant leaks from seals, plugs and casings
- Lubricate the wheel bearings as per the labels
- Remove chutes and supporting components as required to enable the machine to move to or from either the operating position or the maintenance position
- Ensure personnel are clear of the machine prior to tramming
- Ensure the locating pins are retracted prior to tramming
During tramming:
- Check for abnormal noises and vibrations
- Check power absorption and voltages against rated values on nameplates
Wear and rejection criteria
Take note of wear on the following Sizer components to determine the next steps that need to be taken.
Drives
Unusual noises coming from the drives should be investigated immediately. Abnormal noises, griding or meshing noises from gear reducers are a possible indication of bearing or gear meshing failures. The equipment should be shut down immediately and the situation should be investigated and resolved.
Machine frame
The machine frame is protected by wear liners. A proper maintenance schedule must be observed to ensure wear liners are replaced prior to wearing through.
Wear plates and liners
Wear plates and liners are installed where structural components would come into direct contact with the processing material during machine operation. Wear liners and fasteners should be checked in accordance with the maintenance schedule.
Crushing segments and breaker bar caps
As the crushing segments, teeth and breaker bar caps wear, the ability of the machine to process and size feed material to the design requirements will be reduced. Oversize will begin to increase with the increased wear on the segments and breaker bar caps. If the segments, teeth and caps are protected from wear via additional wear plates and/or hard facing, ensure this is maintained to extend the life of the component. Re-application of wear plates and/or hard facing should be scheduled into maintenance activities.
Condition monitoring
To help facilitate maintenance strategies, consider adding a condition monitoring package to your Sizer. Condition monitoring packages can be installed on any new or existing piece of equipment to provide a more comprehensive picture of machine health. These tailored packages utilize a variety of sensors to analyze conditions such as temperature, vibration, motor current, and more.
How does condition monitoring benefit you in terms of maintenance?
First, condition monitoring can help detect the potential for failures before they happen. Meanwhile, you can ensure you have the necessary spares in your inventory or get them on order. You can also plan to replace the wearing component on your terms rather than being surprised with a breakdown.
Condition monitoring also allows you to predict maintenance to improve your strategy beyond a calendar event. You can determine whether maintenance windows need to be moved up or pushed back, depending on the condition of the machine.
In short, condition monitoring helps to reduce unexpected downtime.
By following a preventative maintenance plan involving daily, weekly, monthly, quarterly, semi-annual and yearly inspections, as well as ensuring proper lubrication of all applicable components, you can be sure your Sizer will operate at its best for a long time. Adding a condition monitoring package can further improve your maintenance strategy by providing a comprehensive picture of your Sizer’s health.
