Weathertight Mushroom Ventilator with Handwheel, GB 3887 Type B Cargo Hold

Product Specification

Weathertight Mushroom Ventilator with Handwheel, GB 3887 Type B Cargo Hold Ventilation for Ship Decks

Product Overview

The GB 3887 Type B marine mushroom ventilator is a handwheel-operated weathertight ventilation terminal for exposed ship decks. A centrally arranged handwheel drives a screw mechanism that raises or lowers the internal closing cover against its sealing seat. The arrangement allows the ventilation opening to remain open during normal service and to be closed locally when weather conditions, deck operations, emergency procedures, or inspection requirements demand a weathertight closure.

The supplied legacy size range covers DN 400 to DN 900. GB 3887-1983 is an older standard and is mainly relevant to replacement, repair, or vessel drawings that still specify this configuration. For newbuilding projects, the applicable current standard, deck position, coaming height, fire-safety arrangement, material, and classification requirements should be confirmed before production. Installation in Load Line Position 1 or Position 2 is not determined by the ventilator alone; the complete coaming, deck connection, closing device, and surrounding structure must satisfy the vessel specification and approval basis.

Quick Specifications

• Product type: Type B handwheel-operated mushroom ventilator → local opening and closing of a ship ventilation terminal.
• Legacy standard and size range: GB 3887-1983, DN 400–900 → suitable for replacement or drawing-specified projects after standard-status confirmation.
• Closing principle: central handwheel + left-hand screw spindle + movable cover → positive mechanical travel to the open or closed position.
• Weather protection: mushroom hood and gasketed closing cover → helps prevent direct rain and spray entry when correctly closed and maintained.
• Main reference dimensions: overall diameter 710–1,580 mm and height H 280–360 mm → useful for deck-space, access, and interference checks.
• Reference weight: 98.1–357.4 kg → relevant to handling, deck installation planning, packing, and freight estimation.
• Material and finish: mild steel as the normal structural basis; stainless steel or selected copper-alloy parts can be discussed → final material scope must be confirmed by drawing.
• Optional protection: anti-rodent or insect screen can be specified → fire damper or fire-closing function requires a separate, approved arrangement and must not be assumed.

Main Technical Parameters

Selection & Inquiry Guide

Step 1: Confirm whether the order is a GB 3887-1983 replacement, a vessel-drawing requirement, or a newbuilding project requiring review against the current applicable standard.

Step 2: Confirm nominal diameter DN, ventilation duct or trunk size, required airflow basis, deck position, and available operating clearance around the handwheel and hood.

Step 3: Provide the deck arrangement showing coaming height, deck opening, welded or flanged interface, local reinforcement, drainage condition, and access for inspection.

Step 4: Confirm structural material, spindle and fastener material, gasket type, anti-rodent / insect screen, and whether a separate approved fire damper is required.

Step 5: Confirm surface treatment: Sa 2.5 blasting with epoxy shop primer, final vessel coating system, galvanizing feasibility, or stainless-steel finish where specified.

Step 6: State quantity, vessel type, classification society, inspection and certificate scope, installation drawing, delivery destination, and required delivery time.

Structure

Mushroom hood | Central handwheel | Left-hand screw spindle | Movable weathertight closing cover | Sealing gasket and seat | Ventilator body / coaming | Optional anti-rodent or insect screen | Deck connection interface

Weather Protection, Operation & Maintenance Advantages

• The central handwheel provides direct local control of the closing cover without requiring the complete hood to be rotated, which is practical for larger DN 400–900 ventilators.
• The screw mechanism should move the cover through its full travel so the gasket is released during ventilation and evenly compressed when the unit is closed.
• The mushroom hood shields the opening from direct rainfall and spray; verified weathertight performance depends on the cover reaching its seat, gasket condition, spindle alignment, and structural integrity.
• The closing seat, cover edge, spindle, nut, handwheel, and drainage areas should remain accessible for inspection, cleaning, lubrication, and corrosion control.
• For exposed-deck installation, the ventilator coaming must be structurally connected to the deck and checked together with deck thickness, local reinforcement, coaming height, and the lowest possible water-entry point.
• Routine maintenance should include full-stroke operation rather than only partial handwheel rotation, lubrication of the spindle and nut, and inspection of the cover, coaming edge, gasket, screen, and closing-position indication.
• Anti-rodent or insect protection should be treated as a specified screen component. It must not obstruct the required airflow and should be removable or accessible for cleaning.
• A conventional fire damper is not automatically equivalent to a Load Line weathertight closing appliance. Fire-safety and weathertight functions should be confirmed separately when both are required.

Custom Attributes

• Standard Status: GB 3887-1983 legacy configuration → use for confirmed replacement or drawing-specified projects; review current-standard acceptance for newbuilding.
• Type: B → fixed mushroom hood with central handwheel and screw-operated internal closing cover.
• Nominal Diameter: DN 400 / 450 / 500 / 550 / 600 / 650 / 700 / 750 / 800 / 850 / 900 → select according to the ventilation arrangement and vessel drawing.
• Closing Device: Manual handwheel → confirm operating direction, full travel, closing-position indication, and required access.
• Screw Thread: T36×6-left to T44×8-left → varies with nominal diameter as shown in the detailed engineering table.
• Reference Plate Thickness: Separate seagoing and inland-waterway values → final thickness must follow the confirmed standard, vessel category, and approved drawing.
• Weather Seal: Gasketed closing cover → gasket material, compression, temperature resistance, and replacement details should be confirmed.
• Certificate Requirement: Available according to project scope → maker certificate, material traceability, type approval, or class attendance must be agreed before quotation.

How It Works

Handwheel is rotated → Left-hand screw drives the internal cover upward or downward → Open position allows ventilation through the annular passage beneath the hood → Closed position compresses the gasket against the seat → Crew verifies full closure and maintains the operating mechanism

Applications

Exposed ship-deck ventilation terminals | Freeboard-deck or superstructure-deck ventilation openings subject to approved arrangement | Engine-room or machinery-space ventilation trunks where local weathertight closure is specified | Cargo and service-space ventilation | Newbuilding after current-standard review | Repair and replacement of legacy GB 3887 installations

Certifications & Advantages

Certificates and inspection can be arranged according to project requirement, material traceability, approved drawing, test scope, and classification society procedure.

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

Drawing & Photos

FAQ

Q1: Is GB 3887-1983 still the current standard for marine mushroom ventilators?

A1: No. Official Chinese standard records show that GB 3887-1983 was replaced by CB/T 295-1999; the later CB/T 295-2000 was subsequently replaced by CB/T 4444-2017. The GB 3887 Type B page is therefore best used for legacy replacement or projects whose approved drawing specifically retains this type.

Q2: Can this Type B ventilator be installed in Load Line Position 1 or Position 2?

A2: It can be considered only when the complete arrangement satisfies the applicable Load Line and class requirements. Confirmation should cover deck position, minimum coaming height, lowest possible water-entry point, structural connection, permanently attached or readily available closing appliance, and approved weathertight performance.

Q3: Are anti-rat, insect-proof, and fireproof functions included as standard?

A3: The main Type B function is handwheel-operated weathertight closure. Anti-rodent or insect screens can be specified as accessories. Fire protection requires a separately defined and approved fire damper or closing arrangement; it should not be claimed from the mushroom ventilator structure alone.