Marine Non-Weathertight Small Steel Hatch Cover | CB/T 3728 Type F Single-Point Closure

Product Overview

The CB/T 3728 Type F small steel hatch cover is a hinged marine access cover for openings where a weathertight or watertight boundary is not required. The arrangement combines a steel cover, welded coaming, rubber packing, hinge assembly, and a single dog or butterfly-nut closing point for simple local access. It is intended for protected or otherwise approved locations and should not be specified as a primary exposed-deck weathertight hatch without project approval.

The rubber packing can reduce local splash, dripping, and metal-to-metal contact, and a water-pouring check may be agreed for workmanship verification. Such a check does not change the product classification to weathertight. The vessel designer, shipyard, and classification society should confirm the opening location, protected-space function, coaming height, deck connection, drainage, test scope, and acceptance basis before production.

Quick Specifications

• Product type: Non-weathertight hinged small steel hatch cover → access closure for locations where a certified weathertight boundary is not required.
• Standard reference: CB/T 3728-2011 Type F → used for legacy drawings, replacement work, or project-specific reference; current acceptance should be confirmed.
• Nominal size range: 450 × 630 to 830 × 830 mm → five standard opening formats cover rectangular and square access requirements.
• Clear opening range: 420 × 600 to 800 × 800 mm with R100 corners → supports access planning and cut-out verification against the vessel drawing.
• Coaming height options listed in the supplied data: 100 / 150 / 200 mm → selection depends on deck arrangement, access needs, and project approval.
• Closing arrangement: One dog or one butterfly nut, with M16 / M20 sizes shown in the supplied table → final hardware and compression setting must match the drawing.
• Material options: Mild steel or stainless steel → exact grade, welding consumables, galvanic compatibility, and finishing requirement to be confirmed.
• Type F weight: 22.2 to 54.5 kg excluding coaming → useful for handling, installation planning, packing, and freight estimation.

Main Technical Parameters

Selection & Inquiry Guide

Step 1: Confirm CB/T 3728 Type F, nominal size, clear opening, and whether the request is for a newbuilding, retrofit, or like-for-like replacement.

Step 2: Confirm the installation position, protected-space function, deck cut-out, coaming height, deck plate condition, surrounding reinforcement, hinge side, and opening direction.

Step 3: Confirm that a non-weathertight closure is acceptable. State any required water-pouring check, leakage criterion, survey attendance, or alternative test procedure.

Step 4: Confirm material grade, gasket material, cover and coaming thickness series, closing hardware, corrosion allowance, surface treatment, and final coating compatibility.

Step 5: Confirm certificate scope before quotation: mill / material certificate, maker certificate, class inspection, traceability, NDT, or witness points as required.

Step 6: Provide quantity, application vessel type, installation drawing or photo, delivery destination, required delivery time, and packing or marking requirements.

Structure

Hinged steel cover plate | Welded hatch coaming | R100 clear-opening corners | Rubber packing and seating surface | Single dog or butterfly-nut closure | Hinge pins and brackets | Welded deck interface | Specified corrosion-protection system

Cover, Coaming & Closure Advantages

• The single-point closing arrangement supports quick local access and a simple component layout where uniform multi-dog gasket compression is not required.
• The non-weathertight designation is stated clearly, preventing the cover from being incorrectly selected as a Load Line weathertight or watertight boundary.
• R100 clear-opening corners provide a defined opening geometry and avoid sharp rectangular cut-out corners; the surrounding deck structure still requires drawing review.
• Multiple cover-size and thickness-series options allow the hatch to be matched to the coaming configuration, but the exact t / t0 combination must be confirmed from the standard drawing.
• Gasket seating flatness, hinge alignment, dog position, and controlled compression are key workmanship points for repeatable closing and reduced local water entry.
• For mild-steel supply, blast cleaning and shop primer can support shipyard coating integration; stainless-steel or galvanized options require material and moving-part compatibility checks.
• The welded coaming interface allows integration with the deck structure, while weld detail, distortion control, drainage, and local reinforcement remain project-specific engineering items.

Custom Attributes

• Standard: CB/T 3728-2011 reference → official status is withdrawn; use for legacy, replacement, or specifically approved project requirements.
• Type: Type F → non-weathertight small steel hatch cover with a simple single-point closing arrangement.
• Nominal Size: 450 × 630 / 530 × 530 / 630 × 630 / 630 × 830 / 830 × 830 mm → select against the required clear opening and vessel cut-out.
• Coaming Height: 100 / 150 / 200 mm as supplied → final height must suit the installation position and approved vessel arrangement.
• Closing Type: Hinged cover with one dog or one butterfly nut → M16 / M20 mapping and hardware material to be confirmed.
• Material: Mild steel or stainless steel → exact plate grade and welding requirement to be confirmed before production.
• Packing Material: Neoprene / NBR / HNBR → select according to temperature, oil exposure, aging resistance, and project specification.
• Surface Treatment: Sa 2.5 blast cleaning + one layer epoxy shop primer, polishing, galvanizing, or specified system → final finish depends on material and vessel coating plan.
• Certificate Requirement: Mill / material certificate and inspection documents available according to order scope → class approval is not assumed unless specified.

How It Works

Operator releases the single dog or butterfly nut → Hinged cover opens for local access → Cover is returned onto the rubber packing and seating surface → Closing point is tightened to the agreed compression → Visual and project-specified water-pouring checks are completed

Applications

Protected deck access openings | Internal or sheltered access points | Void spaces where a weathertight boundary is not required | Service and machinery-space access subject to vessel design approval | Legacy replacement projects using CB/T 3728 Type F geometry

Certifications & Advantages

Inspection and certificate documents can be arranged according to project requirement, order scope, material traceability, and classification-society approval procedure. They are not included by default unless stated in the quotation.

Certification: CCS, NK, BV, ABS, DNV, LR, KR, IRS, RS, RINA, CRS, Makers Test Certificate — available upon request and subject to project / class approval.

Drawing & Photos

FAQ

Q1: Is CB/T 3728 Type F a weathertight hatch cover?

A1: No. Type F is described as non-weathertight. Rubber packing and a water-pouring workmanship check may reduce local water entry, but they do not convert the cover into a certified weathertight or watertight closure.

Q2: Can this non-weathertight cover be installed at a Load Line Position 1 or Position 2 opening?

A2: Exposed Position 1 and Position 2 hatchways are generally subject to weathertight closure requirements. Type F should therefore be used only where the vessel design, protection arrangement, Administration, and classification society accept the specific location and space served.

Q3: What information is required for an accurate quotation?

A3: Confirm Type F, nominal size, clear opening, coaming height, cover and coaming thickness series, one-dog or butterfly-nut arrangement, material grade, gasket, surface treatment, installation location, certificate and test scope, quantity, destination, and delivery schedule.