Because of their high-speed rotors, vertical shaft impactors (VSIs) create a dense cloud of dust inside the crushing chamber. The lid seal and other dust sealing elements stop this dust both from spreading into the surroundings and from reaching sensitive parts of the crusher, especially the bearing cartridge. Although it is a small, cheap part, neglecting the lid seal can lead to environmental dust complaints, occupational health risks and early failure of the bearing cartridge.
In this guide we cover the function of the VSI lid seal, material options, wear signs, inspection and replacement steps and spare part selection. For general VSI operation, see our vertical shaft impactor guide.
Function of the Lid Seal
- Prevents dust escape: Stops dust leaving through the joint between the lid and the body.
- Protects the bearing cartridge: Limits dust reaching the area around the cartridge and its seals.
- Controls airflow: By preventing uncontrolled escape of the air current generated inside the crusher, it improves the efficiency of the dust extraction system.
Sealing Points
| Point | Element |
|---|---|
| Lid-to-body joint | Rubber or foam seal strip |
| Feed tube passage | Dust boot or seal |
| Inspection doors | Door seals |
| Around the bearing cartridge | Labyrinth and lip seals |
| Discharge chute connection | Flexible connection and seal |
Material Options
- Rubber profiles: Flexible, economical; moderate wear resistance.
- Polyurethane profiles: More wear resistant.
- Foam seals: Good sealing on uneven surfaces; low wear resistance.
Wear and Failure Signs
- Visible dust escaping from the lid joint,
- Hardening, cracking or breaks in the seal strip,
- Gaps remaining when the lid is closed,
- Dust building up around the bearing cartridge,
- Rising silicon in oil analysis.
Inspection and Maintenance
| Check | Interval | Method |
|---|---|---|
| Dust escape | Every shift | Visual, during operation |
| Seal condition | Every time the lid is opened | Visual and by hand |
| Lid clamping | Every time it is closed | Check for even tightening |
| Around the cartridge | Weekly | Check for dust build-up |
Replacement Step by Step
- The crusher is stopped and LOTO applied.
- The lid is opened and the old seal removed.
- The seating surface is cleaned and residues removed.
- The new seal is placed so that the joints leave no gaps; a suitable adhesive is used if necessary.
- The lid is closed and its clamps tightened evenly.
- Dust escape is checked during operation.
Common Mistakes
- Accepting dust escape as “normal”,
- Leaving gaps at seal joints,
- Not tightening the lid clamps evenly,
- Using unsuitable material.
Troubleshooting Table
| Symptom | Possible cause | Solution |
|---|---|---|
| Dust coming from the lid | Seal worn or broken | Replace the seal |
| Seal deteriorates quickly | Unsuitable material, uneven tightening | Check the material and clamping |
| Silicon in the oil | Dust reaching the bearing area | Check the cartridge and lid seals |
Considering It Together with Dust Control
The lid seal is part of dust control around the VSI. An enclosed design and, if necessary, a dust extraction system should also be used at the discharge chute and the conveyor transfer point. For details, see our article on dust and noise control.
An Example from the Field
At one plant, employees began complaining about the dust around a VSI. It was found that the lid seal had broken in several places and the clamps were not tightened evenly. The seal was replaced with a polyurethane profile and the clamping procedure was standardised. Dust escape fell markedly, and dust build-up around the bearing cartridge also stopped.
Pre-Purchase Checklist
- Have the VSI model and seal profile been identified?
- Has the required seal length been measured?
- Are feed tube and inspection door seals also needed?
Frequently Asked Questions
How often should the lid seal be replaced?
According to condition; it should be checked every time the lid is opened and replaced when damage is seen.
Does dust escape damage the bearing cartridge?
Indirectly, yes; dust building up around the cartridge strains the seals and increases the risk of it getting into the oil.
Can silicone be used instead of a seal?
It is not a permanent solution; it breaks down as the lid is opened. A suitable profile seal should be used.
Where Does Dust Come From in a VSI?
Because of their high rotor speeds, VSIs create a strong airflow inside the crushing chamber. The rotor acts like a fan, pushing air outwards; this air carries with it the fine dust produced during crushing. The main points where dust escapes are:
- The joint surface between the lid and the body,
- The point where the feed tube passes through the lid,
- Inspection and maintenance doors,
- The connection between the discharge chute and the conveyor,
- The feed hopper and feeder area.
For this reason, in VSIs the lid seal should not be dealt with on its own but together with sealing in the feed and discharge areas and, where necessary, a dust extraction system.
Choosing the Seal Material
| Material | Wear resistance | Flexibility | Temperature/oil resistance |
|---|---|---|---|
| Natural rubber | Medium | High | Limited |
| EPDM | Medium | High | Good weather and ozone resistance |
| Polyurethane | High | Medium | Good |
| Foam (cellular rubber) | Low | Very high | Limited |
For crushers working outdoors, materials with good sun and ozone resistance should be preferred, and in winter conditions materials that stay flexible in the cold.
Effect of Operating Conditions on Seal Life
- Frequent lid opening: At plants where rotor checks are frequent, seals wear mechanically faster; choosing a durable profile is important.
- Uneven lid tightening: One area of the seal is over-compressed while another is left loose.
- Sun and ozone: Cause hardening and cracking of rubber.
- Abrasive dust: Wears the seal surface.
Importance for Occupational Health
Respirable crystalline silica dust produced when crushing quartz-bearing rock can cause serious occupational diseases with long-term exposure. For operators and maintenance staff working around a VSI, a sound lid seal is a simple but effective engineering control that reduces dust exposure. Workplace dust measurements can be used to confirm the effect of seal and sealing improvements.
Maintenance Record Form
| Field | Record |
|---|---|
| Inspection date | Together with lid openings |
| Seal condition | Sound / worn / broken section |
| Dust escape observation | None / slight / marked |
| Replacement | Date, material, length |
Stock Planning
- Keep enough spare seal profile in stock to go round one lid.
- Add the feed tube boot and inspection door seals to the spares list.
- Keep suitable adhesive and fitting materials ready.
More Questions
Is a lid seal needed if there is a dust extraction system?
Yes. A dust extraction system creates a slight negative pressure inside the crusher and reduces escape; but if the openings are too large, the system’s capacity is not enough. A sound seal improves the efficiency of the extraction system.
How should seal joints be made?
Joints should be cut to leave no gaps and bonded with a suitable adhesive; where possible, keep joints away from corners.
How long does a seal replacement take?
With the lid open it is usually a short job; planning it for the same shutdown as rotor maintenance is the most efficient approach.
Spare Parts and Service for the Lid Seal
CSP Mühendislik supplies lid seals and sealing elements for vertical shaft impactors as part of its VSI crusher spare parts range, and provides service support for sealing and dust control improvements. Send your VSI model on WhatsApp.
