20" Single-Bolt Flush Manhole (Model #SB540-20-SS) - Stainless Steel

The Model SB540-20-SS features a high-strength stainless steel central bolt mechanism engineered to exert massive, uniform compression across the entire sealing perimeter with minimal effort. This design eliminates the corrosion-related binding common with standard steel fasteners on open decks. When fully tightened into its recessed well, the top remains completely flush with the surrounding surface, allowing seamless cargo operations and unobstructed pedestrian or vehicle movement over the closure.

Intended Use Cases:

• Corrosive Material Tank Access: Specifically designed for direct access into chemical containment holds, liquid cargo tanks, waste storage, or areas continuously washed with harsh chemical sanitizers.
• Potable Water & Food Grade Storage: Non-reactive stainless steel construction makes this model ideal for drinking water tanks and food processing holds on commercial vessels.
• Severe Atmospheric Exposure: Built for open weather decks and swim platforms constantly subjected to high-salinity saltwater spray and extreme ocean elements.

Primary Industries & Vessel Types:

• Chemical & Liquid Cargo Barges: Heavily utilized on specialized liquid-product barges requiring strict non-contamination and chemical resistance.
• Commercial Fishing & Seafood Processing: Built to withstand aggressive organic compounds, blood tracking, and daily high-pressure sanitation cleanings on factory ships.
• Offshore Energy & OSVs: Ideal for extreme ocean states where regular steel components suffer rapid atmospheric pitting and rust.

• Flush Deck Surface: Engineered for a 0" profile height, eliminating tire-damaging or tripping hazards while allowing completely unobstructed movement of forklifts, vehicles, and cargo.
• Single-Bolt High-Torque Mechanism: Simplifies closure down to a single central 7/8" - 9 x 3-1/2" heavy-duty stainless steel bolt, allowing rapid securing and opening while generating maximum, balanced clamping pressure across the sealing perimeter.
• Premium Stainless Steel Construction: Cover plate, frame, and fasteners are crafted from high-grade stainless steel to provide extreme structural integrity, impact resistance, and maximum defense against chemical pitting.
• Rugged Strongback Security: Employs a robust underside stainless steel strongback assembly that anchors firmly against the perimeter rim to guarantee an unyielding, water-tight perimeter seal.
• Buna-N Chemical-Resistant Gasket: Fitted with a premium, industrial-grade Buna-N (Nitrile) rubber gasket that resists swelling or degradation from fuels, oils, and environmental weathering.
• Industrial Clean Finish: Delivered fully finished and polished, offering a professional appearance that eliminates the need for painting, priming, or coating maintenance.

• Qualified Personnel Requirement: Installation of the 20” single-bolt flush manhole must be performed by qualified marine welders or fitters in accordance with applicable classification society standards (ABS, DNV, Lloyd's).
• Stainless Steel Welding Notice: Appropriate stainless steel welding procedures, including correct filler rods and shielding gases, must be utilized when integrating this frame into the deck structure to preserve its corrosion-resistant properties.
• Surface Preparation & Alignment: The mounting frame must be aligned true and securely welded to clean, flat, and structurally sound deck plating to prevent distortion or twisting of the sealing seat.
• Mechanical Verification: After welding, verify that the central stainless steel bolt rotates freely and that the strongback engages the underside lips smoothly without binding or catching.
• Debris Inspection: Prior to final closing, clear all sealing tracks and gasket faces of weld spatter, slag, rust, or excess paint to protect the gasket and ensure a drop-tight seal.