Recessed Marine Manhole Cover with Multi-Bolt Fastening | ISO 5894 Type DO

Product Specification

Recessed Marine Manhole Cover with Multi-Bolt Fastening | ISO 5894 Type DO

Product Overview

The ISO 5894 Type DO marine manhole cover is a long-oval, multi-bolt recessed cover assembly for watertight and oiltight access openings on ships. It is intended for general shipboard use other than pressure vessels and is selected where the surrounding deck, inner bottom, tank top, or passage surface requires a recessed arrangement rather than a raised-coaming or surface-mounted cover.

Type DO combines a standardized clear opening with a bolted cover, gasket, plate ring, surrounding / coaming plate, top cover, handles, and optional jacking-up bolts. Procurement should confirm the clear-opening size, minimum plate thickness, installation depth, gasket medium compatibility, fastener material, structural welding detail, tightness-test scope, and classification requirement before production.

Quick Specifications

• Standard and type: ISO 5894:2018 Type DO / BS ISO 5894:2018 → recessed long-oval manhole configuration for general shipboard watertight or oiltight access.
• Current Chinese equivalent: GB/T 43383-2023 → identical adoption of ISO 5894:2018 for projects specifying the current Chinese national standard.
• Clear-opening sizes: 450 × 350, 600 × 400, 600 × 450, and 800 × 600 mm → four standard access sizes for vessel arrangement and maintenance planning.
• Recessed arrangement: cover assembly is integrated below the surrounding top surface → helps reduce protrusion in deck, inner-bottom, tank-top, or passage installations when fitted to the approved drawing.
• Minimum listed thickness t: 6 to 12 mm → final thickness should be checked against builder practice, surrounding structure, class rules, and project design.
• Fastening: M20 multi-bolt pattern with 16 to 26 fasteners → provides distributed gasket compression around the long-oval sealing perimeter.
• Gasket requirement: suitable for oil, seawater, or fresh water and free from asbestos → exact compound, temperature range, and medium compatibility require confirmation.
• Material and finish: mild steel or stainless steel with project-specified coating, polishing, or galvanizing → exact grades and corrosion compatibility should be confirmed before quotation.

Main Technical Parameters

Selection & Inquiry Guide

Step 1: Confirm ISO 5894 Type DO and select the clear opening 450 × 350, 600 × 400, 600 × 450, or 800 × 600 mm according to the vessel arrangement drawing.

Step 2: Confirm the installation position, required recess depth, surrounding deck / tank-top plating, structural opening, access clearance, and welding interface.

Step 3: Confirm cover, plate-ring, top-cover, and surrounding / coaming-plate thicknesses. The listed t value is a minimum reference and may need to be increased by project design or class requirement.

Step 4: Confirm material grades, fastener and nut material, corrosion compatibility, gasket compound, service medium, operating temperature, and whether optional jacking-up bolts are required.

Step 5: Confirm surface treatment, hydraulic-pressure or tightness-test procedure, acceptance criteria, material traceability, maker certificate, and class inspection scope before quotation.

Step 6: Provide quantity, vessel type, installation drawing or photo, required standard, delivery destination, packing requirement, and required delivery time.

Structure

Long-oval clear opening | Recessed top-cover arrangement | Bolted main cover | Media-compatible gasket | Plate ring | Surrounding / coaming plate | M20 fasteners | Handles | Optional 2 × M20 jacking-up bolts | Welded ship-structure interface

Sealing, Installation & Quality Advantages

• The recessed arrangement keeps the access-cover assembly within the surrounding installation profile when the ship structure and recess depth are prepared to the approved drawing, reducing obstruction in working or passage areas.
• The M20 fasteners are distributed around the long-oval perimeter so the gasket can be compressed around the complete sealing face. Bolt condition, tightening sequence, gasket compression, and sealing-face flatness remain important for tightness.
• Standardized clear-opening dimensions and fastener positions support drawing coordination, replacement planning, and interchangeability of covers and gaskets within the specified standard configuration.
• The long-oval opening provides practical personnel and maintenance access while using less transverse space than a large rectangular opening of similar access length.
• Optional jacking-up bolts can assist controlled separation of the cover after long service periods; this option should be stated in the order and confirmed on the approved drawing.
• Fabrication quality should focus on sealing-face flatness, dimensional control, edge dressing, controlled welding sequence, and distortion management around the plate ring and surrounding structure.
• Material and coating selection should consider the service medium, surrounding tank or compartment, corrosion environment, and compatibility between carbon steel, stainless steel, bronze, or brass fastener options.
• Inspection and testing can be arranged according to the approved project procedure; test pressure, holding time, witnessing, and certificate scope are not assumed unless confirmed in the order.

Custom Attributes

• Standard: ISO 5894:2018 / BS ISO 5894:2018 → use when the vessel specification requires the international Type DO recessed manhole arrangement.
• Chinese Standard Reference: GB/T 43383-2023 → current Chinese national standard identical to ISO 5894:2018.
• Type: DO → long-oval recessed cover configuration with multi-bolt fastening.
• Clear Opening: 450 × 350 / 600 × 400 / 600 × 450 / 800 × 600 mm → select according to access requirement and vessel structure drawing.
• Tightness: Watertight or oiltight → depends on gasket selection, installation quality, bolt tightening, and approved test requirement.
• Fasteners: M20, 16 to 26 pieces → material may be stainless steel, bronze, brass, or other approved option subject to compatibility confirmation.
• Gasket: Oil-, seawater-, or fresh-water-compatible and asbestos-free → exact material and temperature range to be confirmed.
• Main Material: Mild steel or stainless steel → exact plate and component grades to be confirmed before production.
• Surface Treatment: Sa 2.5 blasting plus epoxy shop primer, polishing, galvanizing, or project coating system → select according to material and installation environment.
• Test Requirement: Hydraulic-pressure / tightness test according to approved procedure → test pressure, duration, and witness scope to be confirmed.

How It Works

Ship-structure opening and recess are prepared → Gasket is seated on the clean sealing face → Cover is positioned and M20 fasteners are tightened in a controlled sequence → Gasket compression forms the watertight or oiltight seal → Tightness test is completed according to the approved procedure → Fasteners are released and optional jacking-up bolts assist opening for inspection or maintenance

Applications

Ballast tanks | Fresh-water tanks | Fuel or lubricating-oil tanks with compatible gasket and project approval | Void spaces | Double-bottom spaces | Machinery-space access openings | Deck, inner-bottom, or tank-top passage areas requiring a recessed cover

Certifications & Advantages

Certificates can be arranged according to project requirement, inspection scope, material traceability, and class society approval procedure.

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

Drawing & Photos

FAQ

Q1: What is the main difference between ISO 5894 Type DO and raised or surface-mounted manhole covers?

A1: Type DO is a recessed long-oval configuration intended to keep the cover assembly within the surrounding installation profile. Raised-coaming and surface-mounted types project above the surrounding structure and use different installation details.

Q2: How should the plate thickness, gasket, and fastener material be selected?

A2: The table gives the minimum listed thickness t. Final thickness should be checked against the vessel drawing, surrounding structure, class rules, and project specification. The gasket must match the service medium and temperature, while fastener material should be selected for mechanical performance and corrosion compatibility.

Q3: What information is required to confirm watertight or oiltight performance?

A3: Provide the installation drawing, clear-opening size, material grades, plate thicknesses, gasket specification, fastener material, welding detail, test pressure and duration, inspection witness requirement, and certificate scope. Tightness depends on the complete installed assembly, not the cover plate alone.