API Plan 66B
API Plan 66B – Containment Seal with Restrictive Bushings
API Plan 66B is a leakage containment system designed for single mechanical seals to control and minimize process fluid leakage to the atmosphere.
It uses two restrictive bushings to create a controlled leakage path, reducing emissions and improving safety.
This plan is commonly used in applications where secondary containment is required but without the need for a full dual-seal system.
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Features
How API Plan 66B Works
- Process fluid leakage from the primary seal enters the containment area between the two restrictive bushings.
- The first bushing (closest to the process) restricts leakage flow, creating a pressure drop.
- The second bushing (toward the atmosphere) provides additional containment and controlled venting of small amounts of vaporized leakage.
- Any liquid leakage is redirected back into the pump, minimizing fluid loss.
Comparison with API Plan 66A
- Plan 66A: Uses a single restrictive bushing with a return line to drain small leakage amounts.
- Plan 66B: Uses two restrictive bushings, providing better leakage control and additional containment.
API Plan 66B is an effective leakage containment solution for single seals, offering enhanced safety, emissions control, and reliability without the complexity of dual-seal systems.
Benefits
- Minimizes Process Fluid Emissions – Reduces leakage to the atmosphere by creating a controlled restriction.
- Improves Safety & Environmental Compliance – Helps meet emission regulations in hazardous applications.
- No External Support System Needed – Unlike dual seals, this plan does not require an external barrier or buffer system.
- Enhanced Seal Reliability – Reduces pressure fluctuations and helps maintain stable seal operation.
Drawbacks
- Not a Full Containment Solution – It reduces but does not completely eliminate leakage.
- Requires Proper Bushing Design – Ineffective if bushings are not correctly installed or maintained.
- Limited to Low to Moderate Pressure Applications – High-pressure systems may require a dual-seal system (e.g., API Plan 53).
Applications
- Oil & Gas Industry – Controls hydrocarbon leakage and minimizes fugitive emissions.
- Chemical & Refining Processes – Used where fluid containment is necessary but a full dual-seal system is not required.
- Pumps Handling Toxic or Volatile Fluids – Prevents uncontrolled leaks that could pose environmental or safety risks.
Warning Notes
- Requires Proper Bushing Design
Related Technical Papers
Applicable Products
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