15" x 23" Multi-Bolt Raised Manhole Cover & Frame Only (Model #MB501-1223X) - Painted 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 yard-supplied array of 20 high-tensile 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 and high-pressure fluid containment boundaries where hardware customization is required.

Intended Use Cases:

• Access to fuel oil, ballast, and freshwater storage tanks.
• Inspection hatches for dry voids and cofferdams.
• Removable equipment clearance openings for below-deck machinery servicing.
• Structural retrofits where existing fleet-standard hardware must be reused.

Primary Industries & Vessel Types:

• Ocean-going push boats, tugs, and articulated tug-barge (ATB) units.
• Inland and offshore liquid cargo barges.
• Commercial fishing vessels and deep-sea trawlers.
• Marine infrastructure equipment, dredges, and floating platforms.

• Corrosion-Resistant Primed Steel Construction: Yields exceptional structural rigidity and allows for seamless integration and direct welding into existing steel deck plates.
• Fastener-Ready 20-Hole Pattern: Features precision-drilled bolt holes to accept standard shipyard-supplied fasteners, providing flexibility for custom or fleet-wide hardware standardization.
• 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 the deck opening using the official manufacturer template, then grind the perimeter smooth and clean to bare white metal, ensuring all rust, mill scale, and contaminants are completely removed.
• Welding & Distortion Control: Tack-weld the deck ring flange into the cutout, using a staggered welding sequence to prevent thermal warping, and complete the continuous structural fillet weld according to AWS D1.1 or applicable class society standards.
• Fastener Selection & Procurement: Procure 20 high-tensile, marine-grade fasteners (grade specified by the vessel designer or class society) matching the pre-drilled flange hole diameters.
• 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 20 yard-supplied 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, fastener grades, positioning, and NDT requirements with the vessel designer's specifications and governing class society rules (e.g., ABS, Lloyds, DNV) prior to pressure testing.