18" x 24" Multi-Bolt Raised Manhole (Model #SS502-1824A) - Stainless Steel

This multi-bolt manhole operates as a primary structural closure for access points that do not require frequent or rapid entry. By utilizing a high-density array of 24 high-tensile stainless steel fasteners, the assembly mechanically compresses the commercial-grade Buna-N gasket between the machined cover plate and the deck ring flange. This creates an unyielding barrier against catastrophic flooding, making it ideal for deep-submergence boundaries, chemical storage, and high-pressure fluid containment boundaries.

Intended Use Cases:

• Access to corrosive liquid cargo, fuel oil, ballast, and freshwater storage tanks.
• Inspection hatches for dry voids, cofferdams, and sanitary tanks.
• Removable equipment clearance openings for below-deck machinery servicing in highly corrosive zones.
• Structural retrofits on aluminum or steel hulls requiring high-integrity, low-maintenance closures.

Primary Industries & Vessel Types:

• Chemical tank barges and offshore supply vessels (OSVs).
• Ocean-going push boats, tugs, and articulated tug-barge (ATB) units.
• Commercial fishing vessels, factory trawlers, and live-well vessels.
• Marine infrastructure equipment, naval vessels, and floating production platforms.

• Marine-Grade Stainless Steel Construction: Yields exceptional structural rigidity and ultimate resistance to pitting and crevice corrosion in harsh saltwater environments.
• Heavy-Duty 24-Bolt Securement: Distributes clamping force evenly across the perimeter to prevent cover deflection, eliminate stress concentrations, and guarantee zero-leakage performance.
• Resilient Buna-N Gasket Composition: Delivers superior resistance to marine oils, fuel, and saltwater, ensuring a long-lasting, watertight seal under heavy cyclic loading.
• Raised Coaming Deck Profile: Elevates the sealing surface above the deck level to minimize water exposure and guard against sediment accumulation.

• Deck Surface Preparation: Flame-cut or plasma-cut the deck opening using the official manufacturer template, then grind the perimeter smooth to bare metal, ensuring all slag and contaminants are completely removed.
• Welding & Distortion Control: Tack-weld the stainless steel deck ring flange into the cutout using appropriate filler metal (e.g., 309L for steel-to-stainless joints), employing a staggered welding sequence to prevent thermal warping, and complete the continuous structural fillet weld.
• Anti-Galling Fastener Preparation: Apply a high-quality, marine-grade anti-seize lubricant to all 24 stainless steel bolt threads prior to assembly to prevent mechanical galling and thread seizure during tensioning.
• Debris Inspection & Cleaning: Thoroughly inspect the interior seat and seal channel for weld spatter, slag, or grinding grit before inserting the gasket or attempting to close the hatch plate.
• Gasket Seating & Torque Sequence: Verify the Buna-N gasket is seated flat and uniform within its groove without twists, then hand-tighten all 24 bolts before applying final torque in a progressive star/cross-weave pattern to ensure uniform mechanical compression.
• Vessel Class Compliance: Cross-reference all final weld profiles, positioning, and NDT requirements with the vessel designer's specifications and governing class society rules (e.g., ABS, Lloyds, DNV) prior to pressure testing.