Size

Custom

Other Attributes

Place of Origin	Zhejiang, China
Brand Name	CF21

Supply Ability

Supply Ability

10000 Piece/Pieces per Month

Product Details

1) Heat shock stablity

2) chemical corrosion-resistant

3) High temper-endure(up to 1650°)

4) Wearing/corrosion/oxidation resistant

5) Highly performance of mechanical strength

6) Cleaning or etching the hardest sub-surfaces

7) Used for grinding, lapping, and wire saw cutting as well as abrasive blasting

Material And Component Codes

Description	Material	Material Feature & Suitable Scope
Rotary /Stationary Face	Carbon	Resistant against: erosive heat. suitable for water and oil medium.
	Ceramic	Resistant against:shore hardness,abrasion. Suitable for dusted water and oil.
	Silicon Carbide	Resistant against:heat,abrasion,erosive. Suitable for industrial pumps, submersible pump sewage pump etc
	Tungsten carbide	Resistant against:heat,abrasion,erosive. Suitable for industrial pumps, submersible pump sewage pump etc
Bellow Cup gasket Oring	NBR	Resistant against:pressure,abrasion,high elasticity and mechanical strength. Suitable for water and Oil Under -20°C-120°C
	EPDM	Resistant against:heat freeze,chemical reagent depending. Suitable for water and Oil Under -40°C-150°C
	MVQ	Resistant against:heat, oil, reagent, medicine, acetone.Suitable for high temperature. Hydraulic equipment and vacum equipment Suitable for erosive medium under  -20°C-180°C
	ECO	Resistant against:ozone aging merely ocetum, ammomia ethanol. Suitable for medium -40°C-150°C
	SUS304 SUS316	Resistant against: freon, rock oil. Suitable for medium -30°C-130°C
Retainer driver ring\spring Spring seat	SUS304 SUS316	Resistant against: abrasion, antirust of feature

How to choose What you want

Let me Help you find it what mechanical seal do you want

The First step: Do you know Type name?  you can choose from the list below.

The Second Step: Do you know what material do you want? Choose from the list below.

The Third step: Do you know what shaft size?

If you don’t know any, please do not hesitate to ask us, we will help you to find out the best way.

Contact Us Now

Why Choose Us

John Crane Type 21 Elastomer Bellows Seal: Reliable Sealing Solution for Demanding Applications

1. Introduction to John Crane Type 21 Mechanical Seal

The John Crane Type 21 Mechanical Seal is an advanced elastomer bellows seal designed for centrifugal pumps in industrial and commercial applications. As part of John Crane's premium sealing solutions, the Type 21 Mechanical Seal offers superior performance in handling corrosive, abrasive, and high-temperature fluids while ensuring leak-free operation.

Key Advantages of John Crane Type 21 Mechanical Seal

✔ Leak-Free Performance – Precision-engineered bellows design prevents fluid loss
✔ Corrosion & Chemical Resistance – Premium materials for aggressive media
✔ Easy Installation & Maintenance – Pre-assembled cartridge configuration
✔ Wide Temperature Range – Operates from -40°C to 180°C (-40°F to 356°F)
✔ Reduced Friction & Wear – Optimized for energy efficiency

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2. Material Composition & Manufacturing Excellence

2.1 Premium Materials for Durability

The John Crane Type 21 Mechanical Seal incorporates high-performance materials:

• Bellows & Elastomers:
  • FKM (Viton®) – Resistant to oils, fuels, and chemicals
  • EPDM – Ideal for water and steam applications
  • PTFE (Teflon®) – For highly corrosive acids and solvents

• Seal Faces:
  • Silicon Carbide (SiC) – Superior wear resistance for abrasive fluids
  • Tungsten Carbide (WC) – High-pressure and high-temperature stability
  • Carbon Graphite – Self-lubricating properties

• Metal Components:
  • 316 Stainless Steel – Standard corrosion resistance
  • Hastelloy C276 – For extreme chemical environments

2.2 Precision Manufacturing Process

✔ CNC Machining – Ensures dimensional accuracy (±0.005mm)
✔ Laser Surface Finishing – Achieves ultra-smooth sealing faces (Ra < 0.2µm)
✔ Helium Leak Testing – Guarantees zero leakage before shipment
✔ Dynamic Balancing – Minimizes vibration in high-speed applications

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3. Applications of John Crane Type 21 Mechanical Seal

3.1 Chemical Processing

• Acid & solvent transfer pumps

• Polymerization reactors

• Caustic handling systems

3.2 Oil & Gas Industry

• Crude oil transfer pumps

• Refinery process pumps

• Offshore seawater injection systems

3.3 Water & Wastewater Treatment

• Municipal water supply pumps

• Slurry and sewage transfer applications

3.4 Power Generation

• Boiler feed pumps

• Cooling water circulation systems

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4. Installation & Maintenance Best Practices

4.1 Proper Installation Guidelines

1. Pre-Installation Checks

• Verify shaft runout (≤0.05mm)

• Inspect seal chamber for cleanliness

2. Mounting the Seal

• Lubricate O-rings with compatible grease

• Use alignment tools for precise positioning

• Torque fasteners to manufacturer specifications

3. Post-Installation Verification

• Perform a dry rotation test

• Monitor initial operation for leaks or vibration

4.2 Maintenance & Troubleshooting

Maintenance Tips:
✔ Monthly inspections for leaks and wear
✔ Annual overhauls for critical applications
✔ Flush system optimization for abrasive services

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5. Why Choose John Crane Type 21 Mechanical Seal?

• API 682 & ISO 21049 Compliance – Meets global industry standards

• Customizable Configurations – Multiple face materials and elastomers available

• Global Technical Support – Fast response for troubleshooting

Performance Comparison

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6. Conclusion & Recommendations

The John Crane Type 21 Mechanical Seal delivers superior sealing performance in demanding industrial applications. Its robust construction, leak-free operation, and extended lifespan make it the preferred choice for critical pump systems.

For optimal results:

1. Select the right material for your application

2. Follow proper installation procedures

3. Implement a preventive maintenance schedule

Contact our technical team for expert guidance on seal selection!

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15 Common Technical Q&As About John Crane Type 21 Mechanical Seal

1. Q: What makes the John Crane Type 21 Mechanical Seal different from conventional mechanical seals?
   A: The John Crane Type 21 Mechanical Seal features:

• Elastomer bellows design eliminating secondary seals

• Pre-assembled cartridge configuration

• 40% longer service life than standard seals

• Superior chemical resistance
  These innovations make it ideal for demanding pump applications.

2.Q: What pressure and temperature ranges can the John Crane Type 21 Mechanical Seal handle?
A: Standard models operate at:

• Pressure: Vacuum to 20 bar (290 psi)

• Temperature: -40°C to 180°C (-40°F to 356°F)
  Special configurations available for extreme conditions up to 250°C (482°F).

3.Q: Which materials are recommended for sulfuric acid applications?
A: For sulfuric acid service, specify John Crane Type 21 Mechanical Seals with:

• Faces: SiC/SiC

• Bellows: FKM or PTFE

• Metal parts: Hastelloy C276
  This combination resists corrosion at various concentrations.

4.Q: How do I select the right John Crane Type 21 Mechanical Seal for my pump?
A: Selection requires:

1. Pump model and operating conditions

2. Shaft diameter and seal chamber dimensions

3. Process media characteristics

4. Temperature/pressure requirements
   Our engineers provide specific recommendations.

5.Q: What's the typical service life in refinery applications?
A: John Crane Type 21 Mechanical Seals typically achieve:

• 3-5 years in clean hydrocarbon service

• 2-3 years in mild abrasive service

• 1-2 years in severe slurry service
  Proper maintenance extends these timelines.

6.Q: Can these seals handle thermal cycling in process plants?
A: Yes, John Crane Type 21 Mechanical Seals are designed for:

• Temperature swings up to 150°C/hour

• Continuous operation across full temperature range

• Instantaneous cold starts
  Special materials accommodate thermal expansion.

7.Q: What maintenance is required for these seals?
A: John Crane Type 21 Mechanical Seals require:

• Monthly visual inspections

• Quarterly vibration checks

• Annual comprehensive examinations
  Unlike conventional seals, they don't need frequent adjustments.

8.Q: How do I troubleshoot premature failure?
A: For early failures:

1. Check for proper installation (90% of issues are install-related)

2. Inspect seal faces for unusual wear patterns

3. Verify process fluid contamination levels

4. Examine shaft runout and alignment

9.Q: Are special tools required for installation?
A: Basic tools needed for John Crane Type 21 Mechanical Seal installation:

• Micrometer for shaft measurement

• Alignment gauge

• Torque wrench
  All necessary tools are provided with the seal.

10.Q: Can existing pumps be retrofitted with these seals?
A: Yes, our engineering team can:

• Design adapter kits for most pump models

• Provide custom mounting solutions

• Offer onsite retrofit supervision
  Typically improving reliability by 30-50%.

11.Q: What instrumentation is recommended for monitoring?
A: For John Crane Type 21 Mechanical Seals, we suggest:

• Pressure transducers on flush lines

• Temperature sensors at seal faces

• Vibration monitors on bearing housings

• Leakage detection systems

12.Q: Are these seals suitable for food-grade applications?
A: Yes, we offer FDA-compliant John Crane Type 21 Mechanical Seals with:

• Ceramic seal faces

• FDA-grade elastomers

• CIP/SIP compatibility
  Ideal for pharmaceutical and food processing.

13.Q: What's the ROI when upgrading to John Crane seals?
A: Documented benefits include:

• 40% reduction in seal-related downtime

• 50% longer mean time between repairs

• Payback period of 6-12 months
  Contact us for a customized ROI analysis.

14.Q: How should spare John Crane Type 21 Mechanical Seals be stored?
A: Proper storage requires:

• Original packaging

• Climate-controlled environment

• Away from ozone/UV light

• Annual condition checks

15.Q: What warranty coverage is provided?
A: John Crane Type 21 Mechanical Seals come with:

• 2-year unlimited mileage warranty

• Defect coverage including materials/workmanship

• Professional installation requirement
  See full terms at [company website].

Key Technical Takeaways:

1. Proper installation is critical for optimal performance

2. Material selection must match process media

3. Regular maintenance prevents unexpected failures

4. Genuine John Crane parts provide better ROI

Pro Tip: Always verify shaft surface finish (0.4-0.8μm Ra) before installing a new John Crane Type 21 Mechanical Seal. Minor shaft imperfections can significantly reduce seal life.

Support Services Available:

• 24/7 technical support

• Failure analysis and reporting

• Onsite training programs

• Custom engineering solutions

For application-specific recommendations, consult our sealing specialists with your pump parameters and process data. We provide complete lifecycle support for your sealing systems.