Internally Operated Marine Mushroom Ventilator | CB/T 295-2000 Type A, DN150-350

Product Specification

Internally Operated Marine Mushroom Ventilator | CB/T 295-2000 Type A, DN150-350

Product Overview

The CB/T 295-2000 Type A marine mushroom ventilator is an internally operated hood ventilator for open-deck ventilation trunks. An internal handwheel turns the screw rod to raise or lower the mushroom hood, allowing the opening area to be adjusted from inside the duct or compartment. It is used in natural or mechanically assisted ventilation arrangements where the vessel drawing specifies a Type A internally operated configuration.

The assembly includes the hood, sealing packing, locking arrangement, screen, screw rod, air pipe, and handwheel. Standard nominal diameters cover DN150 to DN350. The air-pipe height h is project-specific, and the stated ventilator mass excludes the air pipe. CB/T 295-2000 is a legacy standard that has been replaced by CB/T 4444-2017; the required edition and approved drawing should therefore be confirmed for newbuilding, repair, or replacement orders.

Quick Specifications

• Product type: Internally operated marine mushroom ventilator → the hood opening is adjusted by a handwheel located inside the ventilation trunk.
• Standard and type: CB/T 295-2000 Type A → suitable for legacy drawings and replacement projects; confirm CB/T 4444-2017 for current-standard requirements.
• Nominal diameter range: DN150 / 200 / 250 / 300 / 350 → five standard sizes for matching the vessel ventilation duct or coaming.
• Opening mechanism: Screw rod with internal handwheel → provides progressive opening adjustment and controlled closure of the hood.
• Main selection dimensions: D1, H, H1, thread d, operating length L, and thickness t → used to check deck clearance, duct connection, and operating space.
• Air-pipe height: h is project-specific → support ribs should be included when the air pipe height above deck exceeds 900 mm.
• Material options: Mild steel, stainless steel, bronze, or copper → exact grade, component compatibility, and approved material combination must be confirmed.
• Surface treatment: Sa 2.5 blasting plus epoxy shop primer, galvanizing, polishing, or a project coating system → select according to material and vessel corrosion-protection specification.

Main Technical Parameters

Selection & Inquiry Guide

Step 1: Confirm the governing standard and configuration: CB/T 295-2000 Type A for a legacy or replacement order, or CB/T 4444-2017 when the current edition is required.

Step 2: Confirm nominal diameter DN, deck opening or duct size, available hood clearance, air-pipe height h, and whether support ribs are required when h exceeds 900 mm.

Step 3: Confirm the ventilation duty and arrangement: natural or mechanical ventilation, supply or exhaust service, compartment served, and required screen type.

Step 4: Confirm material and component requirements, including body material, screw rod, handwheel, sealing packing, screen material, and any corrosion or galvanic-compatibility restrictions.

Step 5: Confirm surface preparation, primer or final coating, galvanizing or polishing requirement, inspection scope, material traceability, and classification-society requirement.

Step 6: Provide quantity, vessel type, installation position, approved drawing or reference photo, delivery destination, and required delivery time.

Structure

Mushroom hood | Sealing packing | Locking / brake pin | Rodent- and insect-proof screen or fire screen as specified | Screw rod | Air pipe | Internal handwheel | Support ribs when required

Ventilation, Operation & Quality Advantages

• Internal handwheel operation allows the opening to be adjusted from a sheltered position below deck, reducing the need to access the exposed weather deck for routine opening and closing.
• The screw mechanism provides progressive hood movement rather than only a fixed open or closed position, helping the crew regulate the free opening area according to the ventilation requirement.
• The mushroom-shaped hood shields the vertical duct opening from direct rain entry during normal ventilation. The required closed-position tightness and any hose or weather test should be confirmed by the project specification.
• Sealing packing provides a defined contact surface when the hood is lowered. Packing material, compression, replacement access, and temperature or fire requirement should be confirmed before production.
• Smooth hood edges, aligned screw movement, and controlled fabrication reduce binding, distortion, and sharp local surfaces that could affect operation or inspection.
• For tall air pipes, the support-rib requirement should be coordinated with the deck structure and installation drawing so that local vibration and movement are properly controlled.

Custom Attributes

• Standard: CB/T 295-2000 → legacy marine mushroom ventilator standard; confirm the required edition against CB/T 4444-2017.
• Type: A, internally operated hood ventilator → opening and closing are controlled by the handwheel inside the ventilation trunk.
• Nominal Diameter: DN150 to DN350 → select according to the vessel ventilation duct, deck opening, and approved drawing.
• Operating Method: Screw rod and handwheel → raises or lowers the hood to adjust the ventilation opening.
• Air-Pipe Height: h to be confirmed → support ribs are required when the height above deck exceeds 900 mm according to the referenced Type A arrangement.
• Material: Mild steel / stainless steel / bronze / copper → exact grade and component combination must be confirmed before quotation.
• Surface Treatment: Sa 2.5 blasting + epoxy shop primer / galvanized / polished / project coating → final system depends on material and vessel specification.
• Certificate Requirement: Available according to order scope → maker certificate, material certificate, class certificate, or witness inspection must be agreed before production.

How It Works

Internal handwheel rotates → Screw rod raises the mushroom hood → Air passes through the annular opening around the hood → Handwheel adjustment changes the free opening area → Screw rod lowers the hood onto the sealing packing for closure

Applications

Accommodation ventilation trunks | Galley ventilation trunks | Service-space ventilation | Natural ventilation inlets or outlets | Mechanical ventilation duct terminations | Open-deck newbuilding and replacement projects

Certifications & Advantages

Certificates can be arranged according to project requirement, material traceability, inspection scope, and classification-society approval procedure. Availability is subject to the agreed order scope and class approval.

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

Drawing & Photos

FAQ

Q1: What is the main operating feature of CB/T 295 Type A?

A1: Type A is operated from inside the ventilation trunk. Turning the handwheel moves the screw rod and raises or lowers the hood, so the opening area can be adjusted without operating the unit from the exposed deck side.

Q2: Is CB/T 295 Type A automatically a certified weathertight ventilator?

A2: The hood and sealing packing provide a closable weather-protective arrangement, but the exact tightness designation, test method, and acceptance criteria should be confirmed from the governing standard edition, vessel specification, and approved drawing.

Q3: What information is required for quotation?

A3: Confirm standard edition, Type A, DN, air-pipe height h, material grades, screen type, sealing requirement, surface treatment, quantity, certificate scope, installation drawing, destination, and required delivery time.