The rotor of a vertical shaft impactor (VSI) turns at high speed on a vertical main shaft. The compact unit that carries this shaft and its bearings, with its own lubrication arrangement and seals, is called the bearing cartridge (some manufacturers call it the shaft line). It is the VSI’s most critical mechanical unit: a bearing cartridge failure can damage the rotor and even the crusher body. On the other hand, with correct lubrication, clean seals and a balanced rotor, bearing cartridges run trouble-free for many years.
In this guide we cover in detail the construction of the bearing cartridge, lubrication types, monitoring parameters, failure signs, replacement and overhaul steps and spare part selection. For general VSI operation, see our vertical shaft impactor guide.
Construction of the Bearing Cartridge
- Main shaft: Carries the rotor at its upper end and the drive pulley at its lower end.
- Bearings: Heavy-duty bearings carrying radial and axial loads.
- Cartridge housing: A cylindrical housing containing the bearings and lubrication passages.
- Seals: Prevent dust ingress and oil leakage.
- Lubrication arrangement: Oil bath, circulating oil or grease, depending on the design.
- Sensors: Temperature, vibration and, in some designs, oil flow sensors.
Lubrication Types
| Type | Characteristics | Maintenance |
|---|---|---|
| Oil bath / drip | Simple, self-contained oil | Level checks, periodic changes |
| Circulating lubrication | With pump, filter and cooler | Flow, temperature, filter and analysis |
| Grease lubrication | Greased at set intervals | Correct quantity and interval |
Whatever the type, monitoring the oil level and temperature and keeping the oil clean determines bearing life. For general information on lubrication systems, see our lubrication unit guide.
Parameters to Monitor
| Parameter | Interval | Meaning |
|---|---|---|
| Oil level | Every shift | A low level means overheating and friction |
| Oil/bearing temperature | Continuous | A rise indicates friction or a cooling problem |
| Vibration | Continuous | Imbalance or bearing damage |
| Oil quality | Periodic analysis | Water, metal particles, sludging |
| Belt tension | Weekly | Excessive tension strains the lower bearing |
Failure Signs
- A gradual or sudden rise in oil temperature,
- The vibration switch tripping frequently,
- A changing sound from the cartridge (humming, ticking),
- Oil leakage or water/particles in the oil,
- Irregular rotation of the rotor when idling,
- Uneven belt wear.
Bearing Cartridge Replacement
Many operations keep a spare bearing cartridge to shorten VSI downtime. The faulty cartridge is removed and the spare fitted, while the faulty cartridge is overhauled in the workshop ready for the next change.
- The crusher is stopped and LOTO applied; the rotor is confirmed to have stopped completely.
- The lid, feed tube and rotor are removed (with a rotor lifting device).
- The belts and pulley are removed.
- The cartridge mounting bolts are removed; the cartridge is lifted out with the manufacturer’s lifting device.
- The cartridge seat is cleaned and checked.
- The spare cartridge is fitted and the bolts tightened to the manufacturer’s torque.
- The pulley, belts and rotor are refitted; belt tension is set.
- The oil level is checked; temperature and vibration are monitored during an idle run.
Workshop Overhaul of the Cartridge
- Dismantling the cartridge in a clean environment,
- Measuring and inspecting the bearings, shaft and housing bores,
- Renewing the bearings and seals,
- Assembly, preload/clearance setting and a rotation test,
- Filling with oil and storing in protective packaging.
Common Mistakes
- Not checking the oil level daily,
- Straining the cartridge by upsetting rotor balance (replacing a single tip),
- Over-tensioning the belts,
- Bypassing the vibration switch,
- Opening the cartridge in a dirty environment.
Troubleshooting Table
| Symptom | Possible cause | Solution |
|---|---|---|
| High temperature | Low oil level, dirty oil, excessive belt tension | Check the level, oil quality and belts |
| Vibration alarm | Rotor imbalance, bearing damage | Check the rotor and tips; inspect the cartridge |
| Water in the oil | Seal damage, condensation | Renew the seals, change the oil |
| Oil leakage | Seal damage | Seal replacement |
An Example from the Field
At a sand plant, a VSI bearing cartridge was frequently overheating. It turned out that the oil level was not being checked every shift and that the level was falling slowly because of a small seal leak. The seal was renewed, a level check was added to the shift list and a spare cartridge was taken into stock. At the next planned shutdown, the cartridge change was completed within a few hours.
Pre-Purchase Checklist
- Have the VSI make/model and cartridge type been identified?
- Is a complete cartridge or an overhaul kit needed?
- Have the bearing and seal part numbers been obtained?
- Is the oil/grease type in use known?
Frequently Asked Questions
Is it necessary to keep a spare cartridge?
At plants where production depends on the VSI, a spare cartridge reduces downtime from days to hours and usually pays for itself quickly.
How often is a cartridge overhauled?
According to monitoring data and the manufacturer’s recommendation; temperature and vibration trends are the best indicators of when an overhaul is due.
Does rotor balance affect cartridge life?
Directly; replacing rotor tips and cavity plates in opposite pairs extends cartridge life.
Root Causes of Bearing Cartridge Failures
| Root cause | Mechanism | Prevention |
|---|---|---|
| Rotor imbalance | Periodic additional load on the bearings, fatigue | Replacing tips and plates in pairs, cleaning inside the rotor |
| Low oil level | Oil film breakdown, overheating | Level check at the start of each shift |
| Oil contamination | Abrasive wear | Seal maintenance, oil analysis |
| Excessive belt tension | High radial load on the lower bearing | Correct tension and alignment |
| Incorrect assembly | Wrong clearance or preload | Manufacturer’s procedure and measurement |
| Heating and insufficient cooling | Oil degradation | Check the cooler and airflow |
Reading Vibration and Temperature Data
The most effective way to monitor the condition of a bearing cartridge is to record vibration and temperature values over time and follow the trend:
- Vibration rising immediately after a rotor tip change: Usually a balance problem; check the rotor, not the cartridge.
- Vibration rising slowly over weeks: May be bearing wear or build-up inside the rotor.
- Temperature rising with increasing load: Can be a normal relationship; but a rising temperature at the same load is a warning sign.
- A sudden temperature rise: Loss of oil or a lubrication failure; the crusher must be stopped immediately.
For a predictive maintenance approach, see our predictive maintenance guide.
The Spare Cartridge Cycle
At plants where the VSI is critical to production, a “swap and overhaul” cycle is used:
- There is a cartridge running on site and an overhauled spare cartridge in the store.
- When monitoring data shows an overhaul is due, the cartridges are swapped at a planned shutdown.
- The removed cartridge is overhauled in the workshop, tested and stored in protective packaging.
- The serial number, overhaul date and operating hours of each cartridge are recorded.
This cycle limits downtime to hours, even in the event of an unexpected cartridge failure.
Storage Tips
- The spare cartridge should be stored in a dry, clean, vibration-free place.
- During long-term storage, the shaft should be turned by hand at intervals to prevent static marks forming in the bearings.
- The cartridge should be protected against corrosion and its openings closed.
Maintenance Record Form
| Field | Record |
|---|---|
| Cartridge serial number | On site / in store |
| Installation date and operating hours | Hour meter reading |
| Oil level and temperature | Daily |
| Vibration value | Continuous or weekly |
| Oil analysis | Water, metals, viscosity |
| Overhaul history | Parts replaced and findings |
OEM or Aftermarket?
Because the bearing cartridge is a precision unit running at high speed, the quality and correct type of the bearings used in an overhaul are critical. For aftermarket cartridges or overhaul kits, the bearing type and clearance class, shaft dimensional tolerances, seal compatibility and the rotation/vibration test after assembly should be documented. Bearings should be sourced from authorised and reliable suppliers.
More Questions
Can a cartridge be overhauled on site?
Because it requires a clean environment and suitable equipment, a workshop overhaul is recommended.
How often is the cartridge oil changed?
At the interval specified by the manufacturer and according to oil analysis results; if water or metal is detected, an early change is required.
How does belt tension affect the cartridge?
Excessive tension puts a high radial load on the lower bearing and shortens its life; tension should be kept at the manufacturer’s value.
Spare Parts and Service for the Bearing Cartridge
CSP Mühendislik supplies bearing cartridges and bearing and seal kits for vertical shaft impactors as part of its VSI crusher spare parts range, and provides service support for cartridge replacement and workshop overhauls. Share your VSI model on WhatsApp for a quick quote.
