Raised Multi-Bolt Oval Manhole Cover | JIS F 2304 Type A Watertight Ship Access

Product Specification

Raised Multi-Bolt Oval Manhole Cover | JIS F 2304 Type A Watertight Ship Access

Product Overview

The JIS F 2304 Type A raised oval manhole cover is a manually secured ship access closure used where personnel inspection or maintenance access is required through a deck, bulkhead, tank boundary, or other approved ship structure. Type A combines a raised oval coaming with a removable cover and multiple perimeter bolts, allowing the gasket to be compressed around the full opening when the fasteners are tightened in a controlled sequence.

For the supplied construction, the gasket seating ring is cut as one complete steel piece rather than assembled from several butt-welded ring segments. This reduces discontinuities across the seating face and supports flatness control, surface finishing, and more uniform gasket compression. Final tightness duty, coaming height, material combination, bolt and nut materials, gasket compound, welding details, test method, and certificate scope must be confirmed against the installation drawing and project requirements.

Quick Specifications

• Standard and type: JIS F 2304 Type A → raised oval coaming with a removable multi-bolt cover for ship access openings.
• Current standard status: JIS F 2304:2015 is the active edition and replaced JIS F 2304:1989 → the contractual edition should be stated on the inquiry and purchase order.
• Nominal sizes: 4535 / 5040 / 6040 / 6045 → four standard opening combinations from 450 × 350 mm to 600 × 450 mm.
• Fastening arrangement: 20 to 24 perimeter bolts → distributes gasket compression around the oval sealing line when tightened in sequence.
• Reference mass: 52.9 to 73.1 kg → cover handling, lifting assistance, access clearance, and maintenance procedure should be considered.
• Standard material basis: SS400 or SM400 steel for cover and coaming → stainless steel construction or alternative materials require drawing and approval confirmation.
• Gasket and fasteners: oil-resistant or ageing-resistant rubber with steel / SUS304 fasteners as standard references → neoprene, Buna-N, brass nut, or other project options should match the service medium.
• Raised coaming: 100 mm reference height from the supplied specification, with customization available → final height depends on installation position, class rules, and approved vessel drawing.

Main Technical Parameters

Selection & Inquiry Guide

Step 1: Confirm JIS F 2304 Type A, the required standard edition, and nominal name 4535 / 5040 / 6040 / 6045 according to the vessel drawing and clear access opening.

Step 2: Confirm installation position, surrounding deck or bulkhead structure, raised coaming height, available cover-removal space, handling arrangement, and welding interface.

Step 3: State the required boundary duty: watertight, oil-tight, or other specified tightness. For gas-tight service, provide the medium, design pressure, temperature, gasket requirement, and acceptance test criteria.

Step 4: Confirm cover and coaming material, bolt and nut material, corrosion compatibility, gasket compound, and whether a handle or other handling feature is required.

Step 5: Confirm surface treatment: Sa 2.5 blasting and epoxy shop primer, final vessel coating, galvanizing feasibility, stainless steel finishing, or another approved system.

Step 6: Provide quantity, class society and certificate requirement, approved drawing or reference photo, delivery destination, and required delivery time.

Structure

Removable oval cover plate | Raised oval coaming | One-piece cut gasket seating ring | Continuous gasket | Multi-bolt perimeter fastening | Optional handling feature | Welded ship-structure interface | Specified surface treatment

Sealing, Fabrication & Installation Advantages

• The raised coaming positions the sealing line above the surrounding plating and provides a defined welded interface for deck, bulkhead, or tank-boundary installation.
• A one-piece cut seating ring avoids butt-spliced ring joints across the gasket face, supporting machining or grinding control and a more continuous sealing surface.
• Multiple bolts distribute clamping around the oval perimeter. Tightening sequence, bolt condition, lubrication, and final compression should follow the approved installation and maintenance procedure.
• The oval opening provides practical personnel access while keeping the overall footprint lower than an equivalent large rectangular access opening.
• Material selection can be coordinated with the surrounding ship structure and service environment. Dissimilar metals require corrosion and galvanic compatibility review.
• Gasket material should be selected by fluid exposure, temperature, ageing resistance, compression behaviour, and replacement availability rather than by product name alone.
• Dimensional inspection should cover clear opening, seating-face flatness, cover fit, bolt-hole alignment, coaming geometry, and welding preparation before delivery.
• Hydrostatic or air leakage testing can be arranged according to the agreed project procedure; test pressure, duration, medium, and acceptance criteria are not assumed without written confirmation.

Custom Attributes

• Standard: JIS F 2304 Type A → current public standard reference is JIS F 2304:2015; confirm whether the order requires the current or legacy 1989 edition.
• Nominal Name: 4535 / 5040 / 6040 / 6045 → designation corresponds to the clear opening combinations shown in the parameter table.
• Opening Size: 450 × 350 to 600 × 450 mm → select according to personnel access, inspection task, and vessel arrangement.
• Construction: Raised oval coaming with removable multi-bolt cover → suitable where a bolted access closure is required rather than a quick-opening hatch.
• Cover / Coaming Material: SS400 or SM400 standard reference → stainless steel or other material is subject to project drawing and approval.
• Fastener Material: Steel or SUS304 bolt; steel, brass, or SUS304 nut as standard references → alternative bronze / brass combinations require confirmation.
• Gasket: Oil-resistant or ageing-resistant rubber / equivalent → neoprene, Buna-N, or customized material should be selected for the actual medium and temperature.
• Coaming Height: 100 mm reference / customized → verify against freeboard, tank, deck, bulkhead, and class requirements.
• Inspection, Certification & Finish: leakage testing, inspection documents, and surface treatment can be arranged according to project requirement → confirm test parameters, witnessing, certificate scope, and coating or finish before quotation.

How It Works

Cover is positioned on the clean gasket seat → Perimeter bolts are installed and tightened in a cross sequence → Gasket is compressed around the oval sealing line → Boundary tightness is verified under the agreed test condition → Bolts are released and the cover is removed when access is required

Applications

Ship decks | Watertight bulkheads | Tank access openings | Machinery-space boundaries | Inspection and maintenance access | Newbuilding projects | Repair and replacement projects

Certifications & Advantages

Inspection documents and classification involvement can be arranged according to the project specification, material traceability requirement, test scope, and class approval procedure. Type approval or EC MED approval should not be assumed unless specifically confirmed for the selected construction and supply scope.

Certification: CCS, NK, BV, ABS, DNV, LR, KR, IRS, RS, RINA, CRS, Makers Test Certificate.

Drawing & Photos

FAQ

Q1: Should the product page quote JIS F 2304:1989 or JIS F 2304:2015?

A1: JIS F 2304:2015 is the current active edition and replaced the 1989 edition. The supplied size table for Type A remains consistent with the listed Type A nominal names, but the quotation and drawing should clearly state the edition required by the shipyard, owner, or replacement project.

Q2: Can the same Type A manhole be specified as watertight, oil-tight, and gas-tight?

A2: Not automatically. The required medium, design pressure, temperature, gasket compound, bolt arrangement, welding details, and test acceptance criteria must be confirmed. Gas-tight duty in particular requires project-specific engineering and testing confirmation.

Q3: What information is required before quotation?

A3: Confirm standard edition, Type A nominal name, opening and coaming height, installation position, material, fastener and gasket materials, tightness duty, test method, coating, quantity, class requirement, drawing, destination, and delivery time.