Both-Side Operated Weathertight Small Steel Hatch Cover with 4 Dog Clips | CB/T 3728 Type B

Both-Side Operated Weathertight Small Steel Hatch Cover with 4 Dog Clips | CB/T 3728 Type B

Product Overview

The CB/T 3728 Type B small steel hatch cover is a hinged weathertight access closure operated from both sides of the opening. Four individually operated dog clips compress the sealing gasket against the coaming landing surface, allowing routine access while maintaining the specified weather-exposed closure function when the cover, gasket, dogs, hinges, coaming, and surrounding structure are correctly selected and installed.

This page is limited to the four-dog Type B arrangements for nominal sizes 450 × 630, 530 × 530, 630 × 630, and 630 × 830. The larger 830 × 830 and 830 × 1230 arrangements use six and eight dogs respectively and should be treated as separate configurations. Coaming height, plate thickness, opening direction, gasket compound, material grade, test scope, and classification requirement must be confirmed against the vessel drawing and the approved project specification.

Quick Specifications

• Product type: Hinged weathertight small steel hatch cover → compact access closure for weather-exposed shipboard openings.
• Operation: Opened and closed from both sides → crew can operate the dog clips from either side of the served opening; emergency-escape suitability requires separate approval.
• Closing arrangement: Four individual wedge-handle dog clips → distributed gasket compression around the cover perimeter and simple local adjustment.
• Four-dog nominal sizes: 450 × 630 / 530 × 530 / 630 × 630 / 630 × 830 mm → separates this page from the six-dog and eight-dog Type B variants.
• Cover plate options: 4 / 6 / 8 mm in the supplied data → select with the coaming thickness, opening size, installation location, and approved drawing.
• Coaming height: Decided by the final user or ship designer → reference heights listed in the supplied data are 100 / 150 / 200 / 250 / 450 / 600 mm.
• Gasket options: Neoprene / NBR / Hi-NBR → final compound should match seawater exposure, oil contact, temperature, and project requirements.
• Inspection options: Hose test and chalk test according to the agreed procedure → test pressure, nozzle distance, duration, and acceptance criteria remain project-specific.

Main Technical Parameters

Main webpage data for the four-dog CB/T 3728 Type B configurations. Dimensions are in mm unless otherwise stated. Weight is exclusive of the coaming.

Selection & Inquiry Guide

Step 1: Confirm CB/T 3728 Type B, the four-dog closing arrangement, and nominal size 450 × 630, 530 × 530, 630 × 630, or 630 × 830 according to the vessel opening and access requirement.

Step 2: Confirm installation position, weather exposure, opening orientation, hinge side, available swing clearance, and whether the hatch is for newbuilding or replacement.

Step 3: Confirm clear opening, coaming height, cover plate thickness, coaming plate thickness, deck or superstructure reinforcement, and welding interface from the approved drawing.

Step 4: Confirm material grade for cover and coaming, dog and hinge material, gasket compound, corrosion-protection system, and any stainless-steel or galvanizing requirement.

Step 5: Confirm inspection scope before quotation: dimensional inspection, operation check, hose test, chalk test, material traceability, maker certificate, class attendance, or other project requirement.

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

Structure

Formed / stiffened steel cover plate | Continuous sealing gasket | Welded steel coaming | Four individually operated dog clips | Both-side operating handles | Hinge assembly | Inside opening-assistance tube / lever | Shop-primer, galvanized, polished, or specified finish

Sealing, Operation & Engineering Advantages

• Four dog clips apply compression at distributed positions around the cover perimeter. Correct dog adjustment is essential; excessive tightening should not be used to compensate for a distorted cover, uneven landing surface, or damaged gasket.
• Both-side operation allows the clips to be released and secured from either side of the opening. The final handle arrangement, internal clearance, and anti-entrapment requirement should be checked against the vessel safety plan.
• The formed or stiffened cover plate helps control local flexing so that gasket compression remains more uniform around the perimeter under normal service and handling conditions.
• The coaming top and gasket landing surface should remain flat, smooth, and free from weld distortion, coating build-up, sharp edges, and local damage that may interrupt the sealing line.
• Hinge alignment, pin condition, opening angle, and the inside opening-assistance tube / lever affect practical operation. These parts should be checked for interference before final welding and coating.
• Neoprene, NBR, and Hi-NBR offer different resistance to weathering, oil, fuel splash, temperature, and ageing. The gasket compound should therefore be selected by service exposure rather than by hatch size alone.
• Hose testing and chalk testing provide different checks: the chalk test indicates gasket contact continuity, while the hose test checks leakage resistance under the agreed test procedure. Neither test should be described without project-specific acceptance criteria.

Custom Attributes

• Standard Reference: CB/T 3728-2011 Type B → manufacture to this dimensional arrangement when it is specifically required by the contract or replacement drawing.
• Closing Type: Four individual dog clips → suitable for the four nominal sizes listed on this page; larger Type B sizes use additional dogs.
• Operation: Both-side opened / closed → individual clips can be operated from either side of the served opening.
• Nominal Size: 450 × 630 / 530 × 530 / 630 × 630 / 630 × 830 → select by clear opening, access requirement, and available installation space.
• Material: Mild steel or stainless steel → exact grade and compatibility of dogs, hinges, fasteners, and welding consumables to be confirmed.
• Packing Material: Neoprene / NBR / Hi-NBR → final seal compound follows exposure, temperature, and owner specification.
• Surface Treatment: Sa 2.5 blasting + one layer epoxy shop primer as reference → galvanizing, polishing, or project coating can be discussed when technically suitable.
• Certificate Requirement: Available according to order scope → maker certificate, material certificate, inspection record, and class certificate are subject to project requirement and approval procedure.

How It Works

Close the hinged cover onto the gasket landing surface → Engage the four dog clips from the accessible side → Tighten the clips in a balanced sequence → Gasket compression forms the weathertight sealing line → Release the clips and use the hinge / opening-assistance arrangement for access

Applications

Weather-exposed deckhouse openings | Superstructure access openings | Dry stores | Service compartments | Routine access positions on cargo ships, workboats, tugboats, barges, and service vessels | Newbuilding and replacement projects

Certifications & Advantages

Inspection and certification can be arranged according to the agreed material traceability, test scope, classification society procedure, and project approval requirement.

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

Drawing & Photos

FAQ

Q1: Which Type B sizes belong to the four-dog configuration?

A1: The standard arrangement shown for this page uses four dogs for nominal sizes 450 × 630, 530 × 530, 630 × 630, and 630 × 830. The 830 × 830 and 830 × 1230 arrangements use six and eight dogs respectively and should not be mixed into the four-dog product page.

Q2: What determines whether the hatch remains weathertight after installation?

A2: Weathertight performance depends on the complete sealing system: cover stiffness, coaming flatness, continuous gasket contact, dog adjustment, hinge alignment, welding distortion control, coating condition, and the agreed inspection procedure. A hose test or chalk test should follow the project-specific method and acceptance criteria.

Q3: Can CB/T 3728-2011 Type B be used for a new project or emergency escape?

A3: CB/T 3728-2011 can still be quoted as a legacy dimensional arrangement when specifically required, but its current acceptance should be confirmed with the ship designer and classification society. The hatch should not be promoted as an emergency escape, liquid-tank access, fire-rated hatch, or watertight/submersible closure unless those functions are separately designed, tested, and approved.

Main Technical Parameters:

Drawing of CB/T 3728 Type B Weathertight Small Steel Hatch Cover with 4 Dogs Marine Outfitting