Marine Mushroom Ventilator with Axial Fan | GB 3887 Type C Weather Deck Ventilation

Product Overview

The GB 3887 Type C marine mushroom ventilator is a weather-deck ventilation terminal configured with an externally operated weather-tight closing cover and an axial-flow fan for mechanical supply or exhaust service. The mushroom-shaped hood limits direct rain entry while the raised cover provides an airflow path around the hood. The assembly is normally connected to a deck ventilation trunk or fan foundation and should be coordinated with the vessel ventilation plan, deck opening, coaming arrangement, fan duty, and maintenance access.

This page covers the user-supplied GB 3887-83 Type C dimensional range DN400 to DN1200. GB 3887-1983 is a legacy standard reference and remains relevant for replacement equipment, old vessel drawings, and like-for-like supply. For newbuilding projects, the governing standard, approved drawing, current CB/T requirement, fan specification, material grade, closing test, and classification scope should be confirmed before production.

Quick Specifications

• Product type: Marine mushroom ventilator with axial-flow fan → combines a weather-deck air terminal, closable cover, and mechanical airflow source in one coordinated assembly.
• Standard and type: GB 3887-1983 Type C, legacy reference → intended for projects that specifically identify this type; current-standard acceptance should be confirmed for new construction.
• Supplied dimensional range: DN400–DN1200 → eleven listed sizes for matching existing deck trunks, replacement drawings, and ventilation openings.
• Ventilation mode: Mechanical supply or exhaust → fan airflow, static pressure, rotation direction, and motor data must be selected from the vessel ventilation calculation.
• Closing arrangement: External handwheel / screw-operated weather-tight cover → allows opening and closing from the exposed deck without entering the ventilated space.
• Material options: Mild steel, stainless steel, bronze, or copper as project options → exact grades, component combinations, and galvanic compatibility require confirmation.
• Surface treatment: Sa 2½ blast cleaning plus epoxy shop primer for carbon-steel construction as a reference → galvanizing, polished finish, or project coating can be specified.
• Quality focus: Hood and trunk geometry, smooth edges, weld quality, sealing-face contact, screw operation, fan alignment, vibration control, and dimensional inspection.

Main Technical Parameters

Selection & Inquiry Guide

Step 1: Confirm the governing basis: GB 3887-83 Type C for replacement / legacy drawing supply, or the current project standard for a newbuilding. State the required DN and provide the vessel or yard drawing when available.

Step 2: Provide the ventilation duty: supply or exhaust, required airflow, external static pressure, fan model, motor power, voltage, frequency, phase, enclosure / IP requirement, insulation class, rotation direction, and any hazardous-area requirement.

Step 3: Confirm the deck and duct interface: opening size, D / D1 / D2 dimensions, ventilation trunk or coaming height, welded or flanged connection, support brackets, drainage arrangement, and available maintenance clearance.

Step 4: Confirm the closing arrangement: external handwheel location, screw thread, cover travel, position indication, sealing packing, closing direction, access for lubrication, and required hose / weather-tightness test.

Step 5: Confirm material and finish: exact material grades for hood, trunk, cover, shaft, screen, and fasteners; carbon-steel coating system; galvanizing; stainless-steel finish; or copper-alloy construction with galvanic-isolation details.

Step 6: Provide quantity, vessel type, installation position, classification society requirement, inspection and certificate scope, delivery destination, required delivery time, and reference photos or existing nameplate information.

Structure

Mushroom-shaped weather hood | Weather-tight closing cover | Sealing packing | External handwheel and left-hand operating screw | Opening-position indication | Protective screen | Ventilation trunk / deck interface | Axial-flow fan assembly | Coating or specified finish

Ventilation, Weather-Tightness & Manufacturing Advantages

• The mushroom hood and closable cover combine weather protection with a controlled airflow opening, making the unit suitable for exposed-deck ventilation terminals where ventilation must also be shut when required by the vessel operating condition.
• External operation allows deck personnel to raise or lower the closing cover from outside. The listed left-hand trapezoidal screw sizes should be matched to the correct DN and checked for smooth travel, lubrication access, and positive position indication.
• Sealing performance depends on the cover geometry, sealing-face flatness, packing material, compression, and operating mechanism. The required hose test, pressure test, or class witnessing should be stated in the order rather than assumed.
• The axial fan must be selected against the actual duct resistance and required airflow. No airflow, pressure, speed, power, noise, or motor rating is inferred from the ventilator DN table.
• Fabrication control should cover circularity of the hood and trunk, dimensional accuracy, vertical alignment, smooth exposed edges, continuous weld quality, fan-to-trunk concentricity, and vibration after fan installation.
• For large DN units, transport lifting points, center of gravity, deck support, local reinforcement, and installation sequence should be reviewed from the approved drawing because the supplied ship weights increase from 113 kg to 689.4 kg.
• Alternative stainless steel, bronze, or copper construction should be engineered as a complete material system, including fasteners, shaft components, fan interface, isolation from carbon steel, and the vessel corrosion-control plan.

Custom Attributes

• Standard: GB 3887-1983 Type C → legacy dimensional reference for old vessel drawings, replacement supply, and project-specific procurement.
• Product Configuration: External opening / closing weather-tight mushroom ventilator with axial fan → mechanical ventilation terminal for exposed deck installation.
• Nominal Diameter: DN400 / 450 / 500 / 550 / 600 / 700 / 800 / 900 / 1000 / 1100 / 1200 → select according to duct size, ventilation calculation, and approved drawing.
• Fan Duty: To be confirmed → airflow, pressure, speed, motor, electrical supply, rotation, noise, and hazardous-area data are not provided in the dimensional table.
• Material: Mild steel / stainless steel / bronze / copper option → exact grade and component-level material schedule should be confirmed before quotation.
• Surface Treatment: Sa 2½ blasting + epoxy shop primer as a carbon-steel reference → final marine coating, galvanizing, pickling / passivation, or polishing follows the project specification.
• Installation: Weather-deck ventilation trunk or fan foundation → deck opening, coaming, welding / flange interface, support, drainage, and local reinforcement require drawing confirmation.
• Certificate Requirement: Available according to order scope → material traceability, maker inspection, class inspection, and fan certificates should be agreed before production.

How It Works

Axial fan starts in the selected supply or exhaust direction → Air moves through the ventilation trunk → Raised closing cover creates an annular flow path beneath the mushroom hood → Hood limits direct weather entry → External handwheel lowers the cover onto the sealing packing when ventilation is to be shut

Applications

Weather-deck mechanical ventilation terminals | Machinery-space ventilation systems | Workshops and general service compartments | Stores and technical spaces according to vessel design | Newbuilding projects subject to current approval | Replacement of legacy GB 3887 Type C units

Certifications & Advantages

Inspection and certification can be arranged according to the project specification, fan supply scope, material traceability, test plan, and classification society approval procedure. Certificates are not assumed to be included unless stated in the quotation and purchase order.

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

Drawing & Photos

FAQ

Q1: Can GB 3887 Type C be used for a newbuilding project?

A1: GB 3887-1983 is a legacy reference. It can be relevant for replacement work or when an existing approved vessel drawing specifically calls for it. For a newbuilding, confirm whether CB/T 4444-2017, another current standard, or a shipyard-specific drawing governs, and obtain class / design approval before production.

Q2: What fan information is required before quotation?

A2: Provide supply or exhaust duty, airflow, external static pressure, fan type and model, speed, motor power, voltage, frequency, phase, IP / enclosure requirement, insulation class, rotation direction, noise limit, hazardous-area requirement, and whether the fan is included in the supply scope.

Q3: Is the ventilator automatically weather-tight when closed?

A3: The Type C arrangement uses a closable weather-resistant / weather-tight cover, but actual sealing performance depends on the approved structure, packing, contact pressure, workmanship, and test requirement. The inspection method and acceptance criterion should be confirmed in the project specification.