Flush Deck Weathertight Small Hatch Cover with Fold-Down Dogs | CB/T 3728 Type D

Product Specification

Flush Deck Weathertight Small Hatch Cover with Fold-Do​wn Dogs | CB/T 3728 Type D

Product Overview

The CB/T 3728 Type D small hatch cover is a flush or recessed deck closure for weather-exposed access openings. The standard drawing identifies it as a quick-acting buried weathertight hatch cover with collapsible dog clips. Its hinged cover plate closes into a welded recessed frame, while perimeter packing is compressed by fold-down dogs to limit water entry under the specified weathertight test condition.

Type D is available in square and rectangular nominal sizes from 530 × 530 mm to 830 × 830 mm. Selection must consider the clear opening, deck cut-out, cover and coaming thickness, number of dogs, hinge side, opening clearance, gasket material, deck reinforcement, and inspection scope. CB/T 3728-2011 is currently listed as an abolished standard; its use should therefore be confirmed for legacy replacement, owner-specified, or project-approved applications. The supplied data supports a weathertight function only. Gas-tight, sound-reduction, fire-rated, pressure-tight, tank-access, or escape-hatch duties require separate design and approval.

Quick Specifications

• Product type: Flush / recessed weathertight small hatch cover → keeps the closed cover close to deck level while providing manual access.
• Standard and type: CB/T 3728-2011 Type D → quick-acting buried arrangement with fold-down or collapsible dog clips; project acceptance must be confirmed because the standard is listed as abolished.
• Nominal size range: 530 × 530, 630 × 630, 630 × 830, and 830 × 830 mm → covers square and rectangular deck access openings.
• Dog quantity: 4 dogs for 530 × 530 and 630 × 630, 6 dogs for 630 × 830, and 8 dogs for 830 × 830 → distributes gasket compression around the perimeter.
• Plate combinations: Cover thickness 4, 6, or 8 mm with coaming thickness 6 or 8 mm according to the listed size variant → affects weight, cut-out dimensions, and installation interface.
• Installation: Welded recessed frame in the deck → deck opening, insert plate, reinforcement, drainage, hinge clearance, and welding distortion must be checked before production.
• Packing options: NBR, high-NBR, or neoprene → final compound and profile should be selected for temperature, weather exposure, oil contact, and project test requirements.
• Tightness verification: Chalk contact check and hose test or agreed equivalent → final procedure and acceptance criteria are subject to shipyard and classification requirements.

Main Technical Parameters

Selection & Inquiry Guide

Step 1: Confirm Type D flush / recessed construction and select the nominal clear opening: 530 × 530, 630 × 630, 630 × 830, or 830 × 830 mm.

Step 2: Select the cover plate and coaming thickness combination, then verify the corresponding cover size, deck cut-out, weight, and fixed dog quantity shown in the table.

Step 3: Confirm deck arrangement: deck plate thickness, recessed frame depth, reinforcement, drainage, hinge on long or short side, opening direction, clear swing area, and whether operation is required from both sides.

Step 4: Confirm material and corrosion protection. Mild steel is the direct basis of the steel hatch standard; stainless steel or aluminium versions require a project-specific drawing, welding details, material compatibility review, and approval.

Step 5: Confirm gasket profile and compound, required weathertight test, service temperature, oil or chemical exposure, and whether any gas-tight or acoustic requirement must be separately engineered and tested.

Step 6: Provide quantity, vessel type, installation position, classification society requirement, approved drawing or reference photo, delivery destination, and required delivery time.

Structure

Flush / recessed cover plate | X-stiffened underside | Fold-down dog clips | Hinges and opening stopper | Continuous perimeter packing | Welded recessed frame / coaming | Deck cut-out interface | Locking or secondary securing provision when required

Sealing, Installation & Quality Advantages

• The recessed Type D arrangement reduces projection above the surrounding deck when closed. This improves passage clearance, but no wheel load, point load, or walk-on rating is declared by the supplied data.
• Four, six, or eight dog clips are positioned according to nominal size so that gasket compression is distributed around the perimeter rather than concentrated at a single securing point.
• Fold-down dog handles reduce protrusion after securing and support quick manual opening and closing. Handle clearance and access from each side must be confirmed on the approved arrangement drawing.
• Frame flatness, cover alignment, hinge geometry, and dog adjustment are critical to uniform gasket contact. Welding sequence and temporary restraint should control distortion during deck installation.
• The packing landing surface and retaining arrangement should be smooth, continuous, and free from weld spatter or coating build-up that could interrupt gasket compression at corners and dog positions.
• Carbon-steel, stainless-steel, and aluminium constructions require different welding consumables, corrosion-control details, and surface treatments. Material substitution should not be treated as a direct one-for-one change.
• For exposed foredeck locations where the applicable class rule adopts IACS UR S26, hinge orientation and an independent secondary securing device may be required in addition to the primary dogs.
• A chalk test can indicate the gasket contact pattern. Final weathertightness should be demonstrated by the specified hose test or an approved equivalent after installation and adjustment.

Custom Attributes

• Standard: CB/T 3728-2011 → legacy Type D dimensional and structural reference; current project acceptance to be confirmed.
• Type: Type D quick-acting buried / flush hatch → recessed deck arrangement with collapsible dog clips.
• Nominal Size and Dogs: 530 × 530 or 630 × 630 with 4 dogs; 630 × 830 with 6 dogs; 830 × 830 with 8 dogs → select by clear opening and deck layout.
• Operation: Hinged cover with fold-down dogs → both-side operation stated in the supplied description must be confirmed by drawing.
• Material: Mild steel standard basis; stainless steel or aluminium by approved project design → grade and welding procedure to be confirmed.
• Packing: NBR / high-NBR / neoprene → compound, profile, hardness, and service limits to be confirmed.
• Surface Treatment: Carbon steel Sa 2½ blast + epoxy shop primer; stainless polished / passivated; aluminium to project coating specification.
• Test and Certificates: Chalk contact check plus hose test / approved equivalent; maker, material, or class documents according to agreed order scope.

How It Works

Lower the hinged cover into the recessed frame → Continuous packing contacts the landing surface → Fold-down dogs are tightened in sequence → Perimeter gasket compression forms the weathertight seal → Dog adjustment and contact are checked → Hose test or approved equivalent verifies the installed closure

Applications

Weather-exposed deck access openings | Dry stores and service compartments | Deck lockers | Machinery or utility-space access subject to escape and fire rules | Newbuilding only when project-approved | Legacy replacement and repair projects

Certifications & Advantages

Certificates and inspection can be arranged according to project requirement, material traceability, approved drawing, test scope, and classification society acceptance. Certificates are not supplied by default and remain subject to class approval.

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

Drawing & Photos

FAQ

Q1: How is the correct Type D hatch cover selected?

A1: Select the nominal clear opening first, then choose the cover and coaming thickness combination. Check the matching cover size, deck cut-out, dog quantity, weight, hinge side, deck reinforcement, and available opening clearance against the vessel drawing.

Q2: Can CB/T 3728-2011 still be used for a new project?

A2: The national standards information platform lists CB/T 3728-2011 as abolished from 12 December 2023. It may still be referenced for legacy replacement or where the owner, shipyard, and class specifically accept it. For newbuilding, confirm the current rule basis and whether GB/T 23426-2009 / ISO 5778 or another approved specification applies. Dimensional interchangeability should not be assumed without drawing review.

Q3: Does the Type D design automatically provide gas-tightness, soundproofing, or two-side operation?

A3: No. The supplied Type D data establishes a weathertight hatch arrangement. Gas-tightness, acoustic performance, fire rating, pressure resistance, and operation from both sides require specific hardware, design details, and acceptance tests shown on the approved project drawing.