The Primary Pantograph Type Roof Sealing System is a mechanical primary seal designed to close the gap between the floating roof and the tank shell in External Floating Roof Tanks (EFRTs). It comprises a series of pivot-connected metal arms (pantographs) that support metallic or non-metallic sealing elements (like stainless steel sheets and vapor barriers), maintaining continuous contact with the tank wall as the roof moves vertically with the liquid level.
This sealing system is engineered to adapt to variations in tank roundness and maintain consistent pressure against the tank shell, thus minimizing evaporative losses and emissions. It is usually the first line of defense in vapor containment.
High Emission Control Efficiency: Effectively limits vapor loss from volatile liquids like gasoline or crude oil.
Durable and Long-Lasting: Constructed from corrosion-resistant materials for long-term use in aggressive environments.
Flexibility: Automatically adjusts to tank out-of-roundness and varying roof levels.
Low Maintenance: Once installed, the pantograph system requires minimal ongoing attention.
Improved Safety: Reduces the formation of explosive gas-air mixtures above the product level.
Regulatory Compliance: Supports compliance with environmental and safety regulations like API 650 and EPA 40 CFR Part 60 Subpart Kb.
Primary Mechanical Seal (used below the floating roof deck, in direct contact with stored liquid vapors).
Crude Oil Storage Tanks
Gasoline, Naphtha, and Jet Fuel Storage
Petrochemical Product Tanks
Fuel Terminals and Refineries
Oil & Gas
Petrochemical
Aviation Fuel Storage
Biofuel Storage Facilities
Chemical Processing
This type of seal is essential in any tank system where large quantities of volatile organic compounds (VOCs) are stored and where regulatory compliance for vapor control is required.
| Parameter | Typical Specification / Range |
|---|---|
| Seal Type | Primary mechanical pantograph seal |
| Seal Element | PTFE or NBR-PVC |
| Pantograph Material | Stainless steel (SS304 or SS316), carbon steel (galvanized/coated) |
| Tank Size Compatibility | Typically up to 100 meters in diameter (custom options available) |
| Seal Gap Range | Accommodates gaps of 150–300 mm |
| Operating Temperature | -40°C to +80°C (special materials available for higher temperatures) |
| Compliance Standards | API 650 Appendix H, API 652, EPA, EN 12285, ISO 28300 |
| Movement Compensation | Axial and radial movement via linked pantograph arms |
Typically installed during tank construction or major maintenance shutdowns.
The pantograph arms are mounted radially on the floating roof deck edge.
Seal plates and vapor barriers are installed to overlap with the tank shell.
Tensioning devices (springs or flex plates) ensure consistent wall pressure.
Visual inspection every 6–12 months for corrosion, misalignment, or fatigue.
Seal tip replacement if hardened, worn, or detached.
Lubrication or adjustment of joints if pantograph arms show reduced mobility.
Cleaning the seal area to remove dirt, sludge, or wax buildup.
VOC Emission Reduction: Major reduction in hydrocarbon vapor loss, which improves local air quality and helps meet air emission regulations.
Fire & Explosion Risk Mitigation: Helps prevent flammable vapor accumulation in the tank headspace.
Supports Regulatory Goals: Critical for meeting environmental laws like the U.S. Clean Air Act or EU VOC Directives.
Product Conservation: Reduces losses of high-value fuels and chemicals due to evaporation.
Recyclable Materials: Use of stainless steel and aluminum allows for easy recycling at end of life.
Passive System: No energy consumption during operation.
Long Service Life: Reduces need for frequent replacement, minimizing material waste.
Seal failure can result in significant VOC emissions, potential fines, and safety hazards.
Corrosion of the pantograph system can lead to seal inefficiency and unsafe conditions.
