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The DF-450 Raised Watertight Expansion Dome addresses a specialized challenge in marine engineering: providing pressure-compensating access to closed fluid systems.
| Quantity: | |
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DF-450-3624
DF-450-3026/3624/4224 RAISED WATERTIGHT EXPANSION DOME
MODEL NO. | ΦA | B | C | ΦD | WT.(lbs) |
| DF-450-3026 | 30" | 26" | 50" | 8" | 750 |
| DF-450-3624 | 36" | 24" | 48 1/2" | 8" | 860 |
| DF-450-4224 | 42" | 24" | 49" | 8" | 950 |
| NO. | Name & Specifications | Qty | Material |
| 1 | HATCH COVER ASSEMBLY | 1 | STEEL |
| 2 | UPPER COAMING RING | 1 | STAINLESS |
| 3 | COAMING ASSEMBLY | 1 | STEEL |
| 4 | HATCH GASKET | 1 | NEOPRENE |
| 5 | CENTER SHAFT | 1 | STAINLESS |
| 6 | I-BEAM SWIVEL ARM | 1 | STEEL |
| 7 | 8"ULLAGE HATCH | 1 | ASSEMBLY |
Leakage test: Pressure 0.04MPa
Other optional extras include: hot dipped galvanized, stainless steel construction, and customing heights
As vessels require reliable access to tanks, pipelines, and reservoirs that experience thermal expansion and contraction, this dome combines watertight integrity with dynamic movement accommodation . Measuring 24 inches in diameter with a raised profile of 12 inches, the DF-450 is engineered to handle volumetric changes in enclosed systems while maintaining a secure seal against water intrusion. Its robust design makes it suitable for fuel storage, ballast tanks, and potable water systems on commercial and military vessels.
The dome incorporates a flexible bellows section that accommodates up to 2 inches of axial movement caused by thermal expansion or pressure fluctuations in the connected system . This movement capability prevents stress on tank walls and piping connections that could lead to leaks or structural damage. The bellows is reinforced with corrosion-resistant wire mesh to prevent over-expansion under pressure.
A dual-seal system combines a primary PTFE-coated neoprene gasket with a secondary O-ring to ensure watertight integrity even during movement . The compression flange features a serrated surface that digs into the gasket material under pressure, creating a secure barrier against water ingress. Testing confirms the seal maintains integrity at pressures up to 5 psi differential between internal and external environments.
The dome body is constructed from 10-gauge carbon steel with a reinforced top plate capable of supporting deck loads up to 400 lbs . The base flange includes pre-drilled mounting holes with oversized washers to distribute loads across the mounting surface. All structural components receive a marine-grade epoxy coating to resist corrosion in submerged or high-moisture environments.
Expansion domes accommodate volumetric changes in closed fluid systems caused by temperature variations, pressure fluctuations, and filling/draining operations . They prevent pressure buildup and vacuum formation that could damage tanks, pipes, or fittings, while providing watertight access for inspection and maintenance.
The reinforced bellows features convolutions designed to flex while maintaining constant compression on the sealing gaskets . The PTFE coating reduces friction during movement and prevents gasket adhesion, ensuring consistent sealing performance through thousands of expansion cycles.
The standard configuration is compatible with fuel oils, diesel, freshwater, and saltwater . For chemical applications, optional Viton gaskets and specialized coatings are available to handle aggressive substances like acids, alkalis, and hydrocarbon solvents.
The bellows and seals should be inspected annually for signs of cracking or degradation . The movement mechanism requires no lubrication, as the PTFE coating provides self-lubricating properties. In high-cycle applications, a complete seal replacement is recommended every 5 years.
Yes, the DF-450 is designed for both above-deck and submerged installations up to a maximum depth of 30 feet (10 meters) when properly installed with the optional deep-water flange kit . The structural design withstands external hydrostatic pressure at this depth while maintaining internal pressure compensation capabilities.
DF-450-3026/3624/4224 RAISED WATERTIGHT EXPANSION DOME
MODEL NO. | ΦA | B | C | ΦD | WT.(lbs) |
| DF-450-3026 | 30" | 26" | 50" | 8" | 750 |
| DF-450-3624 | 36" | 24" | 48 1/2" | 8" | 860 |
| DF-450-4224 | 42" | 24" | 49" | 8" | 950 |
| NO. | Name & Specifications | Qty | Material |
| 1 | HATCH COVER ASSEMBLY | 1 | STEEL |
| 2 | UPPER COAMING RING | 1 | STAINLESS |
| 3 | COAMING ASSEMBLY | 1 | STEEL |
| 4 | HATCH GASKET | 1 | NEOPRENE |
| 5 | CENTER SHAFT | 1 | STAINLESS |
| 6 | I-BEAM SWIVEL ARM | 1 | STEEL |
| 7 | 8"ULLAGE HATCH | 1 | ASSEMBLY |
Leakage test: Pressure 0.04MPa
Other optional extras include: hot dipped galvanized, stainless steel construction, and customing heights
As vessels require reliable access to tanks, pipelines, and reservoirs that experience thermal expansion and contraction, this dome combines watertight integrity with dynamic movement accommodation . Measuring 24 inches in diameter with a raised profile of 12 inches, the DF-450 is engineered to handle volumetric changes in enclosed systems while maintaining a secure seal against water intrusion. Its robust design makes it suitable for fuel storage, ballast tanks, and potable water systems on commercial and military vessels.
The dome incorporates a flexible bellows section that accommodates up to 2 inches of axial movement caused by thermal expansion or pressure fluctuations in the connected system . This movement capability prevents stress on tank walls and piping connections that could lead to leaks or structural damage. The bellows is reinforced with corrosion-resistant wire mesh to prevent over-expansion under pressure.
A dual-seal system combines a primary PTFE-coated neoprene gasket with a secondary O-ring to ensure watertight integrity even during movement . The compression flange features a serrated surface that digs into the gasket material under pressure, creating a secure barrier against water ingress. Testing confirms the seal maintains integrity at pressures up to 5 psi differential between internal and external environments.
The dome body is constructed from 10-gauge carbon steel with a reinforced top plate capable of supporting deck loads up to 400 lbs . The base flange includes pre-drilled mounting holes with oversized washers to distribute loads across the mounting surface. All structural components receive a marine-grade epoxy coating to resist corrosion in submerged or high-moisture environments.
Expansion domes accommodate volumetric changes in closed fluid systems caused by temperature variations, pressure fluctuations, and filling/draining operations . They prevent pressure buildup and vacuum formation that could damage tanks, pipes, or fittings, while providing watertight access for inspection and maintenance.
The reinforced bellows features convolutions designed to flex while maintaining constant compression on the sealing gaskets . The PTFE coating reduces friction during movement and prevents gasket adhesion, ensuring consistent sealing performance through thousands of expansion cycles.
The standard configuration is compatible with fuel oils, diesel, freshwater, and saltwater . For chemical applications, optional Viton gaskets and specialized coatings are available to handle aggressive substances like acids, alkalis, and hydrocarbon solvents.
The bellows and seals should be inspected annually for signs of cracking or degradation . The movement mechanism requires no lubrication, as the PTFE coating provides self-lubricating properties. In high-cycle applications, a complete seal replacement is recommended every 5 years.
Yes, the DF-450 is designed for both above-deck and submerged installations up to a maximum depth of 30 feet (10 meters) when properly installed with the optional deep-water flange kit . The structural design withstands external hydrostatic pressure at this depth while maintaining internal pressure compensation capabilities.
