Small Weathertight Steel Hatch with Wing-Nut Closures | Storage and Dry Cargo Hold Access (ISO 5778)

Small Weathertight Steel Hatch with Wing-Nut Closures | Storage and Dry Cargo Hold Access (ISO 5778)

Product Overview

The ISO 5778 small weathertight steel hatch is a hinged deck access cover secured by wing nuts and toggle bolts. It is intended for loading operations and access to storage compartments or dry cargo holds, with standardized nominal opening sizes and fitting locations supporting interchangeability between compliant hatch assemblies.

The hatch is not intended for access to tanks and must not be used as an escape hatch. Application in Load Line position 1 or position 2 is assessed for each vessel arrangement, and additional cover stiffening may be required. Final coaming height, surrounding deck reinforcement, opening position, drainage, closing-device quantity, gasket material, testing, and class acceptance should follow the approved vessel drawing and applicable statutory requirements.

Quick Specifications

• Product type: Hinged small weathertight steel hatch → access opening for storage spaces and dry cargo holds.

• Standard: ISO 5778:1998 → current international standard, confirmed by ISO in 2026; GB/T 23426-2009 is the current identical Chinese adoption.

• Nominal opening sizes: 630 x 630 to 1,330 x 1,330 mm → based on the inside dimensions of the upper coaming.

• Closing arrangement: Wing nuts with toggle bolts → designed for one-person tightening without tools under normal closing conditions.

• Hinge arrangement: Two hinges with oval holes → allows the closing devices to compress the hatch seal without hinge restraint.

• Hatch seal: 45 x 20 mm resilient section → bonded with marine-suitable adhesive, with 2 mm initial compression allowed and a 4 mm maximum compression stop.

• Coaming and cover geometry: Square or rounded corners → upper coaming edges should be rounded or chamfered to avoid gasket damage.

• Application limit: Not for tanks and not for escape routes → position 1 / 2 use and additional stiffening require project-specific confirmation.

Main Technical Parameters

Main ISO 5778 nominal opening and cover dimensions are shown below. Dimensions are in mm. The coaming dimensions a and b have a tolerance of 0 / -2 mm; cover dimensions a1 and b1 have a tolerance of +/-2 mm.

Engineering note: Cover sizes exceeding 830 x 830 mm require additional stiffening in accordance with the applicable Load Line requirement and approved structural design.

Selection & Inquiry Guide

Step 1: Confirm ISO 5778 nominal size and whether the hatch is for loading access, a storage compartment, or a dry cargo hold.

Step 2: Confirm installation position, Load Line position 1 or 2 where applicable, coaming height, deck opening, surrounding reinforcement, drainage, and available opening clearance.

Step 3: Confirm material grade, cover and coaming thickness, stiffener arrangement for larger sizes, hinge orientation, opening direction, hold-open device, and whether a counterbalance is required.

Step 4: Confirm gasket material and service temperature, wing-nut and toggle-bolt materials, corrosion resistance, thread standard, depth stops, and required spare gasket or fasteners.

Step 5: Confirm surface treatment, final coating, galvanizing or stainless-steel option, gasket-seat masking, thread protection, and shipyard touch-up requirements.

Step 6: Confirm hose or equivalent weathertightness test procedure, class witnessing, certificate scope, quantity, destination, required delivery time, and provide the vessel drawing or reference photo.

Structure

Steel coaming | Hinged steel cover plate | Two oval-hole hinges | 45 x 20 mm resilient hatch seal | Seal retaining bar | Wing nuts | Toggle bolts and pins | Closing lugs | Compression depth stops | Optional hold-open or counterbalance arrangement

Weathertight Sealing, Closing & Fabrication Advantages

• The wing-nut and toggle-bolt arrangement allows normal closing force to be applied by one person without tools, supporting frequent operational access.

• Two hinges with oval holes permit controlled seal compression as the closing devices are tightened, reducing the risk of hinge geometry preventing full gasket contact.

• Compression depth stops limit gasket compression to 4 mm, helping reduce over-compression, permanent set, and premature seal damage.

• The 45 x 20 mm resilient seal is retained mechanically and bonded with marine-suitable adhesive, supporting repeatable sealing when the coaming edge and cover remain correctly aligned.

• Rounded or chamfered coaming edges protect the gasket during repeated opening and closing and reduce exposed sharp edges around the access opening.

• Coaming, cover, and fittings should be free from distortion and rough edges; correct registry and continuous contact between the coaming edge and gasket should be checked during assembly.

• For 1,030 x 1,030 and 1,330 x 1,330 sizes, cover stiffening and deck support require particular attention because the nominal size exceeds 830 x 830 mm.

• A hold-open arrangement and counterbalance can be incorporated where required to improve safe handling, but the final arrangement must follow the approved drawing.

Custom Attributes

• Standard: ISO 5778:1998 → current standard for small weathertight steel hatches; GB/T 23426-2009 is an identical current Chinese adoption.
• Nominal Size: 630 x 630 to 1,330 x 1,330 mm → based on the inside dimensions of the upper coaming.
• Application: Storage compartments / dry cargo holds / loading operations → not suitable for tank access or escape routes.
• Closing Device: Wing nut + toggle bolt → threads follow ISO 262 selected metric sizes in the standard design.
• Hinges: Two per hatch with oval holes → allow gasket compression during closing.
• Hatch Seal: 45 x 20 mm resilient packing → material selected for marine ageing, sealing, and resealing performance.
• Steel Requirement: Weldable steel with minimum tensile strength stated by ISO 5778 → exact project grade and certification to be confirmed.
• Toggle Bolts and Pins: Corrosion-resistant material → exact alloy and mechanical properties to be confirmed before quotation.
• Testing: Hose test or equivalent test according to the regulatory body → chalk testing can support contact checking but does not automatically replace the required weathertightness test.
• Certificate Requirement: Available according to project scope → material traceability, dimensional inspection, test record, and class witnessing should be agreed before quotation.

How It Works

Cover rotates on two hinges → Resilient seal aligns with the rounded coaming edge → Toggle bolts are engaged → Wing nuts are tightened progressively → Oval hinge holes allow controlled gasket compression → Depth stops prevent over-compression → Hose or equivalent testing confirms the agreed weathertightness

Applications

Storage compartments | Dry cargo holds | Loading-access openings | Deck stores | Shipboard service spaces approved for weathertight access | Newbuilding projects | Replacement of ISO 5778 / GB/T 23426 hatches

Certifications & Advantages

Material certificates, dimensional inspection records, coating records, hose or equivalent test reports, maker documentation, and class witnessing can be arranged according to project requirements and the agreed order scope. Certificates are not presented as automatically included with every delivery.

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

Drawing & Photos

FAQ

Q1: Can an ISO 5778 hatch be used as tank access or as an escape hatch?

A1: No. ISO 5778 specifically excludes access to any kind of tank and prohibits use as an escape hatch. A separate tank manhole, watertight hatch, or approved escape closure should be selected for those duties.

Q2: Can the hatch be installed in Load Line position 1 or position 2?

A2: The possibility must be assessed for each installation. Coaming height, cover strength, closing devices, deck structure, exposure, and class requirements must be checked. Additional cover stiffening is required where necessary, particularly for nominal sizes above 830 x 830 mm.

Q3: Is a 0.2 MPa hose test at 2 m an ISO 5778 requirement?

A3: The accessible ISO text requires a hose test or equivalent test acceptable to the regulatory representative, but it does not state those exact parameters in the published requirement reviewed for this page. The 0.2 MPa / 2 m value should therefore be treated as a customer or project test reference until confirmed by the purchased standard, class procedure, or approved inspection plan.

Main Technical Parameters:

Drawing of ISO 5778 Small Weathertight Steel Hatch Cover With Wing Nut Marine Outfitting