150-350 mm Weathertight Marine Mushroom Ventilator | GB 3887-83 Type A

Product Specification

150-350 mm Weathertight Marine Mushroom Ventilator | GB 3887-83 Type A

Product Overview

The GB 3887-83 Type A marine mushroom ventilator is a manually operated, weathertight closing ventilator for ship weather-deck openings. It is intended for small independent compartments, accommodation service spaces, store rooms, and similar spaces where the vessel drawing specifies a compact DN150-DN350 mushroom-type vent with a deck coaming.

The mushroom cap is opened or closed by rotating it along the threaded spindle. When fully lowered, the sealing packing is compressed against the seating surface; a side stop screw retains the selected position. The standard arrangement also shows an anti-rat / anti-insect screen, spindle, handle, and ventilator coaming. For procurement, the key checks are the governing standard, DN and deck opening, coaming height, operating access, material combination, surface treatment, sealing-packing requirement, screen specification, and class inspection scope.

Quick Specifications

• Product type: Manually operated weathertight marine mushroom ventilator → closes an exposed deck ventilation opening without electric, pneumatic, or hydraulic actuation.
• Standard and type: GB 3887-83 Type A → mainly relevant to replacement, repair, and project-specific vessel drawings using the legacy GB configuration.
• Nominal size range: DN150 / 200 / 250 / 300 / 350 → compact range for smaller ventilation openings and independent compartments.
• Opening mechanism: Rotating mushroom cap with left-hand threaded spindle → provides controlled raising, lowering, and compression of the closing packing.
• Position retention: Side stop screw / locking screw → helps retain the cap at the selected open or closed position.
• Sealing and screening: Rubber sealing packing plus anti-rat / anti-insect screen → packing condition and screen mesh should be confirmed for the operating environment.
• Material options: Mild steel, stainless steel, bronze, or copper → exact material grade and compatibility of cap, spindle, screen, fasteners, and coaming are to be confirmed.
• Deck integration: Coaming, weld interface, operating clearance, and support arrangement must match the vessel drawing; the standard note calls for support brackets when the coaming height above deck exceeds 900 mm.

Main Technical Parameters

Selection & Inquiry Guide

Step 1: Confirm that the order is for GB 3887-83 Type A and state whether it is a replacement item, a repair project, or a new vessel requirement. For new designs, confirm the current governing standard with the shipyard, owner, and classification society.

Step 2: Select DN150-DN350 according to the approved ventilation drawing, deck opening or duct diameter, required airflow, and available installation envelope. Airflow capacity is not stated in the supplied data and should not be inferred from DN alone.

Step 3: Provide the installation position, compartment served, weather-deck location, coaming height, deck thickness, weld / flange interface, support bracket requirement, and available access for rotating the cap and operating the side locking screw.

Step 4: Confirm the closing arrangement: sealing-packing material, seating-surface finish, anti-rat / anti-insect screen mesh, any separately required fire-screen function, and the required inspection or hose-test procedure.

Step 5: Confirm material and surface treatment: mild steel, stainless steel, bronze, or copper; Sa 2.5 blasting plus epoxy shop primer for carbon steel; galvanized, polished, or project-specific finish where applicable.

Step 6: State quantity, vessel type, class society requirement, material certificate scope, delivery destination, required delivery time, and provide the original standard drawing, shipyard installation drawing, or reference photo if available.

Structure

Mushroom cap | Sealing packing | Side stop screw | Anti-rat / anti-insect screen | Left-hand threaded spindle | Operating handle | Ventilator coaming | Optional support bracket according to coaming height

Weather-Deck, Sealing & Maintenance Advantages

• The manual screw mechanism uses few moving parts and does not require a power supply, which is suitable for local deck ventilation points that are opened and closed by crew.
• Closing travel is generated through the threaded spindle, allowing the cap to compress the sealing packing against the seating surface rather than relying only on the cap self-weight.
• The side stop screw provides a simple means of retaining the cap position; its engagement, corrosion condition, and accessibility should be checked during routine maintenance.
• The anti-rat / anti-insect screen protects the ventilation opening while allowing airflow. The screen must remain removable or accessible for cleaning and should not be painted or clogged during maintenance.
• The compact DN150-DN350 range supports replacement of older vessel fittings where the deck opening and coaming arrangement have already been fixed by the original drawing.
• For carbon-steel construction, blasting and shop primer protect the fabricated surfaces before installation. Final coating, sealing faces, threads, and moving parts require different treatment controls to avoid obstructing operation.
• The ventilator must be integrated with the vessel's coaming and deck structure. Coaming height, support, weld detail, and weather-deck closing requirements remain part of the ship design and class approval, not only the ventilator supply.

Custom Attributes

• Standard: GB 3887-83 → legacy Type A geometry for replacement and project-specific orders; the governing current standard is to be confirmed for new projects.
• Type: A → compact mushroom ventilator with manually operated cap, sealing packing, locking screw, screen, spindle, handle, and deck coaming arrangement.
• Nominal Size: DN150 / 200 / 250 / 300 / 350 → select against the approved deck opening, duct connection, airflow calculation, and installation space.
• Operating Method: Manual rotation on a left-hand threaded spindle → cap position is adjusted locally by crew.
• Sealing: Rubber packing at the cap / seating interface → packing material, compression, replacement access, and test requirement are to be confirmed.
• Screen: Anti-rat / anti-insect screen → mesh, material, removability, and any fire-screen requirement depend on the project.
• Material: Mild steel / stainless steel / bronze / copper → exact grade and component-by-component material combination are to be confirmed before quotation.
• Surface Treatment: Sa 2.5 blasting + one layer epoxy shop primer, galvanized, polished, or customized → treatment must suit the selected material and vessel coating system.
• Installation: Weather-deck coaming connection → coaming height, deck weld or flange detail, support, and operating clearance follow the vessel drawing.
• Certificate Requirement: Available according to project requirement → maker certificate, material traceability, class attendance, and test documentation must be agreed before order.

How It Works

Ventilation duct connects to the deck coaming → Mushroom cap is rotated on the left-hand spindle to raise the cap → The annular opening allows airflow while the hood sheds rain and spray → Cap is rotated downward to compress the sealing packing → Side stop screw retains the selected position

Applications

Small independent compartments | Accommodation service spaces | Store rooms | Utility rooms | Weather-deck natural ventilation points | Duct-connected ventilation openings | Ship repair and replacement projects based on GB 3887-83 drawings

Certifications & Advantages

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

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

Drawing & Photos

FAQ

Q1: Is GB 3887-83 still the current standard for new ship designs?

A1: GB 3887-1983 is a legacy standard. It remains useful for replacement and repair when the vessel drawing specifies this Type A configuration. For a newbuilding or redesign, the shipyard should confirm whether the current CB/T 4444-2017 standard or another project standard applies.

Q2: How should the correct DN be selected?

A2: Match the DN to the approved deck opening or duct connection and verify the required airflow, pressure loss, installation envelope, coaming height, and crew operating access. The supplied table contains dimensions and weights, but it does not provide airflow capacity, so DN should not be selected from dimensions alone.

Q3: What should be checked before accepting the weathertight closure?

A3: Check the packing material and condition, seating-surface flatness, cap travel, thread engagement, side locking screw, screen installation, coaming connection, and the project-specified closing test. Any class witness or hose-test requirement should be agreed before production.