Bearing Sealing Technology Breakthrough: Comparison Of Z-type And V-type Seals And High-speed Selection Requirements

1. Bearing Seal Technology: Z-Type and V-Type Become Mainstream
With industrial equipment moving toward higher speeds, higher precision, and longer service life, the importance of bearing sealing technology is increasingly prominent. The two most common bearing seal structures currently on the market are: non-contact metal shields (code Z) and contact rubber seals (code V, with some brands using 2RS). The two designs differ significantly in structure, protection capability, applicable speed, and operating environment. Correct selection directly affects equipment reliability and maintenance costs.

According to industry statistics, about 65% of bearings in general industrial motors, fans, and pumps use Z-type metal shields; while in harsh environments such as humid, dusty, or food processing conditions, the application proportion of V-type rubber seals has exceeded 50% and is trending upward year by year.

2. Z-Type Seal (Metal Shield) Technical Characteristics
Z-type seals (common suffixes: Z/ZZ) are non-contact shields made of stamped steel plates installed on both sides of the bearing. There is a certain gap (typically 0.1-0.3mm) between the shield and the inner ring, resulting in no direct friction.

【Table 1: Z-Type Seal Core Parameters】

Parameter Typical Value
Structure Non-contact metal shield
Sealing gap 0.1-0.3mm
Speed limit Highest (100% of bearing limit speed)
Protection capability Protects against large dust particles, not waterproof
Friction torque Very low
Temperature range -30~150°C
Cost Low
The core advantage of Z-type seals is extremely low friction torque and very high speed capability. Since the shield does not contact the inner ring, no additional frictional heat is generated. Therefore, Z-type sealed bearings can achieve the bearing's own maximum speed limit, making them particularly suitable for high-speed operation. Their disadvantage is weak protection against moisture, fine dust, and corrosive gases; they are not suitable for humid or dusty environments.

3. V-Type Seal (Rubber Seal) Technical Characteristics
V-type seals (common suffixes: V/VV or 2RS) are contact seals made of nitrile rubber (NBR) or fluoroelastomer (FKM) installed on both sides of the bearing. The seal lip tightly contacts the inner ring, forming an effective sealing barrier.

【Table 2: V-Type Seal Core Parameters】

Parameter Typical Value
Structure Contact rubber seal
Seal type Single-lip or double-lip contact
Speed limit Approximately 80%-85% of bearing limit speed
Protection capability Waterproof, dustproof, grease retention
Friction torque Higher
Temperature range -40~120°C (NBR) / -20~200°C (FKM)
Cost Moderate
The core advantage of V-type seals is excellent sealing performance. The tight contact between the seal lip and the inner ring effectively prevents moisture, dust, and chemical media from entering the bearing while preventing grease leakage. This design is particularly suitable for harsh environments such as humid, dusty, or frequent washdown conditions, including food processing, agricultural machinery, and outdoor equipment. The trade-off is additional friction torque, resulting in a speed reduction of about 15%-20%, and the seal lip may wear or age over time.

4. Key Differences Between Z-Type and V-Type
【Table 3: Comprehensive Comparison: Z-Type vs. V-Type Seals】

Dimension Z-Type (Metal Shield) V-Type (Rubber Seal)
Contact method Non-contact (gap) Contact (lip contacts inner ring)
Protection target Large dust particles Moisture, fine dust, grease leakage
Waterproof capability None Yes (general waterproof, not for immersion)
Speed limit 100% (baseline) 80%-85%
Starting torque Low High (2-3x larger)
Operating temperature rise Low Higher (due to friction)
Temperature range -30~150°C NBR:-40~120°C; FKM:-20~200°C
Cost Lower Moderate
Typical applications Motors, fans, pumps, high-speed spindles Agricultural machinery, food equipment, power tools
Maintenance requirement Low (virtually maintenance-free) Moderate (periodic seal inspection)

5. What Grade Does a Bearing Need to Achieve at 3000 rpm?
A speed of 3000 rpm (revolutions per minute) falls into the medium-high speed range. Different bearing sizes and types have different requirements for precision grade, clearance, lubrication, and seal type at 3000 rpm.

5.1 Precision Grade Requirements
Bearing precision grades typically follow ISO or ABEC standards, ranging from low to high: P0 (normal), P6 (higher than P0), P5, P4, P2. At 3000 rpm, the recommended precision grades for different applications are:

【Table 4: Recommended Bearing Precision Grades at 3000 rpm】

Application Recommended Grade Rationale
General motor, fan, pump P0 (Normal) 3000 rpm is normal for general motors; P0 meets vibration/noise requirements
General reducer, conveyor P0 Steady load, low precision requirement
Machine tool spindle (3000 rpm) P5 Requires higher rotational accuracy and rigidity
High-speed motor (>3000 rpm) P5 or P4 Reduce vibration, extend life
Precision instruments, aerospace P4 or P2 Extremely high precision required
Important note: For bearings with small bore (e.g., 6200 series, 10mm bore), 3000 rpm is near their rated speed limit; at least P6 grade is recommended. For larger bore bearings (e.g., 6210, 50mm bore), 3000 rpm is well below their speed limit (approx. 8000 rpm), so P0 is sufficient.

5.2 Clearance Grade Requirements
At 3000 rpm, clearance selection must consider temperature rise and fit tightness:

General conditions (temperature rise <50°C) : Normal clearance (CN) is sufficient

Large temperature difference or tight fit: Recommend C3 clearance (larger than normal) to prevent clearance loss from thermal expansion causing seizure

High-speed precision spindles: May require C2 clearance (smaller than normal) to maintain preload

5.3 Lubrication Selection
【Table 5: Recommended Lubrication Methods at 3000 rpm】

Bearing Type Grease Oil Lubrication Notes
Deep groove ball bearing (bore <50mm) Preferred Optional Lithium grease No.2, fill 1/3-1/2 free space
Deep groove ball bearing (bore >50mm) Optional Recommended Grease may cause higher temperature rise
Angular contact ball bearing Grease or oil mist Oil mist better Oil lubrication for high-speed precision
Cylindrical roller bearing Optional Recommended Heavy load, oil better for heat dissipation
5.4 Seal Type Selection (Z vs V) at 3000 rpm
Z-type seals: Fully capable, with speed margin (supports higher speeds). Recommended for dry, clean environments.

V-type seals: Check whether the bearing's speed limit is reduced due to the rubber seal. If the bearing's original speed limit is 4000 rpm, with V-type it drops to 3200 rpm, then 3000 rpm is within the safe range. If the original limit is only 3500 rpm, it drops to 2800 rpm – not suitable.

6. Selection Recommendations: Z or V?
Prioritize Z-type seals when:

Dry operating environment, no dust or only coarse particles

High-speed requirement (near bearing speed limit)

Low friction and low energy consumption needed

Seal wear particles cannot be tolerated

Prioritize V-type seals when:

Humid environment, moisture or condensation present

Fine dust exists (e.g., textile, food industry)

Equipment is frequently washed down (e.g., food processing, car wash equipment)

Grease leakage must be prevented (e.g., vertical shaft mounting)

Long-term operation with minimal maintenance desired