Open-Type Mushroom Ventilator with Flanged Connection | Cargo Hold and Accommodation Ventilation (Legacy CB/T 295 Type D)

Product Overview

The CB/T 295 Type D mushroom ventilator is an open-type deck ventilation terminal with a broad mushroom hood and a flanged lower connection. It is used to provide natural or fan-assisted air intake or exhaust for cargo spaces, service spaces, galleys, and accommodation-related ventilation systems, subject to the vessel ventilation plan and fire-safety arrangement.

Type D is a non-closing head: airflow is controlled by the connected fan, duct damper, fire damper, or other approved downstream device rather than by the mushroom hood itself. Where the ventilator serves a space below the freeboard deck or an enclosed superstructure, the complete installation must satisfy the applicable coaming height, weather protection, and closing-appliance requirements. A shielded ventilator cabin or weather-protected enclosure can form part of the approved arrangement, but the open mushroom head alone should not be presented as a Load Line closing device.

Quick Specifications

• Product type: Open-type mushroom ventilator with lower flange → terminal fitting for natural or fan-assisted marine ventilation.
• Legacy standard and type: CB/T 295-2000 Type D → the 2000 standard is withdrawn and fully replaced by CB/T 4444-2017; dimensional equivalence requires confirmation.
• Nominal diameter range: DN 250 to DN 1400 → covers small service-space outlets through large cargo-hold ventilation openings.
• Airflow control: By connected fan or separate damper → the Type D mushroom head itself remains open and does not provide weather shutoff.
• Main envelope: Hood diameter D1 from 440 to 2,440 mm and overall reference height H from 220 to 800 mm → important for deck clearance, airflow spacing, and transport planning.
• Weight range: 42 to 701 kg from the supplied table → ventilator weight excludes the connected air duct.
• Installation interface: Flanged duct connection → flange drilling, mating duct, gasket, damper, fan, and flexible connection details must be confirmed by drawing.
• Load Line consideration: Exposed ventilators serving protected spaces require an approved coaming and closing / protection arrangement → open Type D should be used only within a compliant complete installation.

Main Technical Parameters

Selection & Inquiry Guide

Step 1: Confirm whether the project requires legacy CB/T 295 Type D dimensions or the current CB/T 4444 standard, and provide the vessel ventilation drawing.

Step 2: Confirm DN, required airflow, system resistance, intake or exhaust duty, natural or powered ventilation, fan connection, and permissible air velocity or noise requirement.

Step 3: Confirm installation location: cargo hold, galley, accommodation-related space, store, workshop, or other compartment; state whether the opening leads below the freeboard deck.

Step 4: Confirm deck position, required coaming height, weather exposure, shielded cabin / enclosure, closing appliance, damper, fire damper, and Load Line or class requirements.

Step 5: Confirm material grade, flange standard and drilling, mating duct size, gasket, support and reinforcement, coating system, galvanizing or polished finish, and corrosion environment.

Step 6: Provide quantity, class society, inspection scope, drawing or photo, delivery destination, required delivery time, and whether fan, damper, transition, or enclosure is included in the supply scope.

Structure

Mushroom hood | Annular air passage | Central support structure | Cylindrical coaming / trunk | Lower connecting flange | Optional separate fan or damper interface | Deck support and reinforcement | Specified coating or corrosion-resistant finish

Ventilation, Weather Protection & Installation Advantages

• The wide mushroom hood shelters the annular air passage from direct vertical rain and falling debris while allowing airflow around the circumference; it should not be treated as a fully weathertight closure.
• The open head creates a low-obstruction terminal compared with a manually closed mushroom ventilator, making it suitable where continuous airflow is required and weather protection is provided by the complete arrangement.
• A flanged lower connection allows the ventilator to be matched with a fan, shut-off damper, fire damper, transition, or duct section without welding the entire ventilation train into one assembly.
• For cargo-hold use, the ventilator arrangement should be coordinated with cargo type, water-ingress risk, fire plan, hold ventilation rate, fan duty, and any requirement to close the opening remotely or locally.
• For galley or accommodation-related service, the terminal should be coordinated with the approved duct route, fire boundary penetrations, fan control, noise, condensate, and cleaning access. The mushroom head alone is not the complete ventilation system.
• Large DN units require support and deck reinforcement review. The Load Line rules also require special support where a ventilator coaming exceeds the specified height threshold.
• Dissimilar materials such as stainless steel, bronze, or copper should be isolated from carbon-steel deck structure where required to reduce galvanic corrosion and simplify coating maintenance.

Custom Attributes

• Product Type: Open-type mushroom ventilator → continuous annular airflow opening without an integral weather-closing cover.
• Standard Reference: Legacy CB/T 295-2000 Type D → withdrawn; current replacement standard is CB/T 4444-2017.
• Nominal Diameter: DN 250-1400 → final selection follows airflow calculation and duct arrangement, not diameter alone.
• Connection: Lower flange → flange drilling, mating flange, gasket, and fasteners to be confirmed.
• Airflow Control: Separate fan / damper / fire damper as required → not built into the open mushroom head unless included by project design.
• Weather Protection: Mushroom hood plus approved complete installation → Load Line compliance depends on coaming, location, enclosure, and closing arrangement.
• Material: Mild steel / stainless steel / bronze / copper options → exact grade and component allocation require confirmation.
• Surface Treatment: Sa 2.5 blasting + epoxy shop primer, galvanizing, polished finish, or project coating → selected according to base material and vessel coating specification.
• Customization: Diameter, flange, coaming height, support, and connected equipment can be adapted to an approved project drawing.
• Certificate Requirement: Available according to project scope → material traceability, dimensional inspection, welding records, and class witnessing should be agreed before quotation.

How It Works

Air is drawn or discharged through the connected duct → Fan or natural pressure difference drives the airflow → Air passes through the flanged trunk → Flow turns through the annular opening below the mushroom hood → Separate damper or approved closing arrangement controls or secures the ventilation system when required

Applications

Cargo-hold ventilation | Galley and service-space ventilation terminals | Accommodation-related ventilation systems | Stores and workshops | Fan-assisted deck ventilation | Natural ventilation openings | Newbuilding and legacy replacement projects

Certifications & Advantages

Material certificates, welding records, dimensional inspection, coating records, functional inspection of supplied dampers, and class witnessing can be arranged according to the project specification and agreed supply scope. The ventilator should not be described as class-approved or Load Line compliant by itself unless the complete installation and certificate scope have been approved.

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

Drawing & Photos

FAQ

Q1: Is CB/T 295-2000 still the current standard for ship mushroom ventilators?

A1: No. The official Chinese standards platform lists CB/T 295-2000 as withdrawn and CB/T 4444-2017 as the current standard that fully replaced it. Legacy Type D dimensions can still be used for replacement or compatibility when specified, but direct dimensional equivalence with the current standard should be confirmed.

Q2: Can an open Type D mushroom ventilator be used directly for cargo-hold ventilation on an exposed deck?

A2: Only as part of an approved complete arrangement. The open head is not a weathertight closing appliance. The coaming height, deck position, shielded cabin or enclosure, closing appliance, fire-safety arrangement, and Load Line / class requirements must be confirmed for the vessel.

Q3: How should the nominal diameter be selected?

A3: DN should be selected from the required airflow, allowable velocity, pressure loss, fan duty, duct size, noise target, opening location, and weather-protection arrangement. The standard dimension table confirms the product envelope but does not replace the ventilation-system calculation.