Recessed Oval Marine Manhole Cover | ISO5894:2018 Type CO Multi-Bolt Design

Recessed Oval Marine Manhole Cover | ISO5894:2018 Type CO Multi-Bolt Design

Product Overview

The ISO 5894:2018 Type CO marine manhole cover is a recessed, oval, multi-bolt access closure for general shipboard structures requiring watertight or oiltight integrity. The nominal size represents the clear opening, with four standard openings from 450 × 350 mm to 800 × 600 mm. Its recessed arrangement is intended for locations where the cover and fasteners must remain within the surrounding deck, tank-top, or structural installation plane.

The assembly normally consists of a steel cover, gasket, plate ring, recessed coaming, handle, marking, and M20 fasteners distributed around the oval perimeter. ISO 5894 defines the clear opening, principal dimensions, and fastener arrangement to support consistent installation and replacement. Final material grades, cover and coaming thicknesses, gasket compatibility, weld details, test procedure, surface treatment, and classification scope should be confirmed against the vessel location and service medium before production.

Quick Specifications

• Standard and type: ISO 5894:2018 Type CO → recessed oval manhole with a multi-bolt cover for general shipboard use.
• Standard scope: Watertight and oiltight bolted access closure → intended for ship structures other than pressure vessels.
• Clear opening range: 450 × 350, 600 × 400, 600 × 450, and 800 × 600 mm → covers common personnel-access and inspection-opening requirements.
• Fastening arrangement: M20 fasteners, 16 to 26 pieces → distributed around the oval perimeter for controlled gasket compression.
• Minimum cover thickness t: 6, 8, 8, or 12 mm according to nominal size → class rules, location, loading, or builder practice may require a greater value.
• Recessed installation: Cover and fastening components are arranged below or within the intended flush plane → recess depth and surrounding structure must match the approved installation drawing.
• Material options: Mild steel or stainless steel construction → exact plate, fastener, and nut grades require project confirmation and corrosion-compatibility review.
• Sealing and testing: Medium-compatible, asbestos-free gasket and project-defined tightness test → test pressure, duration, leakage criterion, and witness scope must be stated in the inquiry.

Main Technical Parameters

Main ISO 5894:2018 Type CO dimensions. All dimensions are in mm. Nominal size l1 × b1 is the clear opening.

Fastener arrangement for the standard nominal sizes.

Selection & Inquiry Guide

Step 1: Confirm ISO 5894:2018 Type CO and select the clear opening from 450 × 350, 600 × 400, 600 × 450, or 800 × 600 mm according to access needs and the vessel drawing.

Step 2: Confirm the installation position, recessed depth, surrounding deck or tank-top thickness, coaming arrangement, structural reinforcement, drainage condition, and available maintenance space.

Step 3: Confirm the required boundary: watertight or oiltight under ISO 5894 scope. Any gas-tight requirement requires separate design criteria, gasket selection, and an agreed verification test.

Step 4: Confirm cover, ring, and coaming material grades; stainless steel or corrosion-resistant fastener grade; nut material; gasket material; service fluid; temperature range; and galvanic-corrosion compatibility.

Step 5: Confirm welding or stud-attachment details, surface treatment, hydraulic or tightness test procedure, material traceability, inspection hold points, and classification society requirement before quotation.

Step 6: Provide quantity, application vessel type, installation drawing or reference photo, delivery destination, required delivery time, packing requirement, and any replacement-interchangeability requirement.

Structure

Recessed oval cover | Medium-compatible gasket | Plate ring | Recessed coaming | M20 multi-bolt fastening | Handle | Optional jacking-up bolts | Identification marking | Welded installation interface

Sealing, Installation & Quality Advantages

• The recessed geometry reduces projection above the surrounding installation plane, which is useful where a raised cover could interfere with deck movement, cargo handling, machinery access, or maintenance routes.
• Standardized clear-opening dimensions and fastener coordinates support dimensional consistency and help replacement projects match the approved cover, gasket, and surrounding structure.
• Multiple M20 fasteners distribute compression around the oval gasket. A balanced cross-tightening sequence helps reduce uneven seating and local leakage risk.
• The gasket should be selected for the actual medium, including seawater, fresh water, fuel oil, or lubricating oil as applicable, and should be free from asbestos.
• Minimum plate thickness is a standard selection basis rather than an automatic project approval value. Local loads, corrosion allowance, deck duty, tank pressure head, and classification requirements can require increased thickness.
• Fastener and nut materials should be checked for mechanical strength, corrosion resistance, thread compatibility, and galvanic interaction with the cover and ring materials.
• Sealing faces, gasket grooves or contact bands, threads, and seating surfaces should be protected during blasting, coating, galvanizing, transport, and shipyard welding.
• Hydraulic or other tightness testing can be arranged according to the approved project procedure. Test pressure, duration, inspection method, acceptance criterion, and witnessing are not to be assumed from the product name alone.

Custom Attributes

• Standard: ISO 5894:2018 → current international standard for shipboard manholes with bolted covers.
• Type: CO → recessed oval configuration with a multi-bolt cover.
• Nominal Size: 450 × 350 / 600 × 400 / 600 × 450 / 800 × 600 mm → values refer to the clear opening l1 × b1.
• Minimum Cover Thickness: 6 / 8 / 8 / 12 mm → select by nominal size; increased thickness may be required by project rules or structural review.
• Fasteners: M20, 16 / 20 / 20 / 26 pieces → quantity varies with the selected clear opening.
• Construction Material: Mild steel or stainless steel → exact grade and minimum mechanical properties to be confirmed before production.
• Fastener and Nut Material: Stainless steel, bronze, brass, or other approved corrosion-resistant combination → mechanical properties and galvanic compatibility require confirmation.
• Gasket: Neoprene, NBR/Buna-N, or project-specified material → selection depends on fluid, temperature, compression, and fire or regulatory requirements.
• Surface Treatment: Sa 2.5 blasting + epoxy shop primer, polished stainless steel, galvanizing, or project coating → sealing and threaded areas require controlled protection.
• Test and Inspection: Hydraulic or tightness test according to approved order requirement → pressure, duration, medium, leakage criterion, and witness scope to be confirmed.

How It Works

Recessed opening and plate ring are installed in the ship structure → Gasket and oval cover are positioned on the seating surface → M20 fasteners are tightened progressively in a balanced sequence → Gasket compression forms the specified watertight or oiltight boundary → Seating, fasteners, coating, and leakage are checked according to the approved inspection and test plan

Applications

Ship decks and tank tops | Ballast tank access | Freshwater tank access | Fuel and lubricating oil tank access | Void spaces and cofferdams | Machinery and service compartments | Newbuilding and replacement projects | General shipboard use excluding pressure vessels

Certifications & Advantages

Material certificates, maker inspection documents, tightness test records, and classification society inspection can be arranged according to the agreed order scope, project specification, and class approval procedure. Certificates are not implied as standard supply unless stated in the quotation.

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 Type CO and a surface-mounted manhole cover?

A1: Type CO is recessed so the cover and fasteners remain within the installation plane; a surface-mounted cover normally projects above the plating. Select the type from the approved vessel drawing.

Q2: How should the nominal size and plate thickness be selected?

A2: Select by the required clear opening and approved vessel drawing. The listed thickness t is a minimum; class rules, local loads, corrosion allowance, tank head, or builder practice may require a greater value.

Q3: Does ISO 5894 Type CO automatically provide gas-tight performance?

A3: No. ISO 5894 covers watertight and oiltight manholes for general shipboard use, excluding pressure vessels. Gas-tight service requires separate design and verification. Test pressure, duration, medium, acceptance criteria, and witness scope must be agreed before production.

Main Technical Parameters:

Key: 1 coaming plate, 3 cover, 2 plate ring, 4 gasket, 5 handle, 6 marking 7 jacking-up bolt, 2 × M20

The weld size and details should meet the recognized industrial standard.

Dimensions given in brackets ( ) can be adjusted. The top of the cover, including the nut, should not protrude from the flush surface when choosing a dimension given in brackets.

NOTE 1 Jacking-up bolts 2 × M20 can be chosen by the user if suitable.

NOTE 2 l 1 х b 1 is a clear opening.

NOTE 3 The type of handle can be designed and changed according to builder practice.

Drawing Of ISO 5894 Type CO Recessed Oval Manhole With Bolted Cover