Flush Oval Marine Manhole Cover | JIS F 2304 Type B Multi-Bolt Tank Access

Product Specification

Flush Oval Marine Manhole Cover | JIS F 2304 Type B Multi-Bolt Tank Access

Product Overview

The JIS F 2304 Type B flush oval marine manhole cover provides low-profile personnel and inspection access through ship decks, tank tops and bulkheads. Its flat seat-ring arrangement and peripheral multi-bolt fastening suit locations where a raised coaming is not required. Typical uses include ballast-water tanks, oil or fuel tanks and void spaces, subject to the approved vessel arrangement and class requirements.

The seat ring can be cut from one continuous steel plate instead of butt-welded segments, helping maintain a continuous sealing plane. Watertight or oiltight performance depends on cover/seat flatness, gasket compatibility, bolt tightening, installation-weld distortion and the agreed test procedure. Gastight service is not assumed unless specifically designed and verified.

Quick Specifications

• Product form: JIS F 2304 Type B flush oval multi-bolt cover → low-profile access for tank tops, decks and bulkheads.
• Standard basis: JIS F 2304:2015 is the current edition and supersedes the 1989 edition → the required edition should be stated in the purchase order.
• Nominal designations: 4 535 / 5 040 / 6 040 / 6 045 → clear openings from 450 × 350 mm to 600 × 450 mm.
• Bolt quantity: 20 to 24 → closely spaced fastening points distribute gasket compression around the oval perimeter.
• Material and hardware basis: SS400 or SM400 cover/seat, with steel or SUS304 bolts and steel, brass or SUS304 nuts under the current JIS edition → alternatives require an approved project specification.
• Gasket selection: oil-resistant or ageing-resistant rubber, including project-selected neoprene or NBR/Buna-N → confirm against tank medium and temperature.
• Reference mass: 42.8 to 59.6 kg → supports lifting, installation, packing and freight planning.

Main Technical Parameters

Selection & Inquiry Guide

Step 1: Confirm Type B, nominal designation and required standard edition: JIS F 2304:2015 or a specifically requested legacy edition.

Step 2: Confirm installation location and orientation, surrounding plate thickness, reinforcement and available flush clearance.

Step 3: State the tank medium, design liquid head or pressure, operating temperature and required tightness; define watertight, oiltight and gastight requirements separately.

Step 4: Confirm cover/seat material, bolt and nut materials, optional handle and any stainless-steel or non-ferrous hardware.

Step 5: Confirm gasket material and coating system for ballast water, fuel oil, lubricating oil or other service.

Step 6: Confirm tests, class and certificate scope, quantity, destination, delivery time and approved drawing or photo.

Structure

Flush oval cover plate | One-piece cut seat ring / pad | Peripheral one-side threaded bolts | Nuts and washers | Replaceable sealing gasket | Optional lifting handle | Welded installation interface

Sealing, Installation and Quality Advantages

• One-piece seat-ring cutting avoids butt joints across the sealing face and supports a continuous gasket contact surface.
• Cover/seat flatness, sealing-face finish and bolt-hole alignment are controlled together because sealing depends on the assembled interface.
• Closely spaced bolts distribute clamping around the oval perimeter; staged crosswise tightening reduces uneven gasket compression.
• Controlled welding sequence and restraint help limit seat-ring distortion; flatness and trial assembly should be rechecked after installation welding.
• Gasket compound, hardness, dimensions and compatibility, plus confirmed cover/seat/bolt/nut/washer materials.

Custom Attributes

• Standard: JIS F 2304:2015 current edition; JIS F 2304:1989 legacy reference → confirm the contractual edition.
• Type: Type B flush oval multi-bolt manhole → selected where a low-profile seat arrangement is required.
• Clear Opening: 450 × 350 to 600 × 450 mm → select by access need and approved vessel arrangement.
• Cover and Seat Material: SS400 or SM400 standard basis → stainless steel requires an approved project specification.
• Bolt and Nut Material: steel, SUS304 and brass options → confirm corrosion and galling compatibility.
• Gasket: oil-resistant or ageing-resistant rubber → select neoprene or NBR/Buna-N by medium and temperature.
• Tightness: watertight or oiltight to project test requirements → gastight performance requires separate verification.
• Surface Treatment: Sa 2½ blasting and epoxy shop primer, galvanizing or project coating → confirm vessel-system compatibility.

How It Works

Tank or compartment is isolated and declared safe → Sealing faces are cleaned → Cover and gasket are positioned → Bolts are engaged → Crosswise staged tightening compresses the gasket → Bolts are released for authorized access

Applications

Ballast-water tank access | Fuel and oil tank access with compatible gasket | Void-space inspection access | Tank-top openings | Internal deck and bulkhead access | Newbuilding and replacement projects

Certifications & Advantages

Maker documentation, material certificates and class inspection can be arranged under the approved inspection and test plan. Class certificates remain subject to project scope, drawing approval, traceability and survey attendance.

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

Drawing & Photos

FAQ

Q1: What distinguishes JIS F 2304 Type B from other manhole types?

A1: Type B uses a flush oval seat and multiple perimeter bolts for low-profile access. Other JIS F 2304 types use different coaming, hinge or seat arrangements; select by the vessel drawing.

Q2: How should the gasket be selected for ballast-water or oil-tank service?

A2: Confirm the stored medium, temperature, ageing resistance, hardness and compression. NBR/Buna-N may suit oil service, but the final compound must follow the approved specification.

Q3: Is hydraulic pressure testing or a class certificate included as standard?

A3: No. The current JIS standard specifies appearance requirements; project leakage/pressure tests and class survey are separate items. Confirm test pressure, duration, acceptance criteria and certificate scope.