NAKAKITA AIR PURGE UNIT

Product Introduction

The Nakakita Air Purge Unit is one of the most reliable pneumatic devices used onboard commercial vessels to protect pressure sensing lines from seawater, sludge, oil, and contamination. It continuously supplies clean compressed air into sensing pipes, ensuring accurate pressure transmission for various marine monitoring systems.

For decades, Nakakita Seisakusho of Japan has supplied highly dependable marine pneumatic equipment to shipyards and vessel operators worldwide. Their Air Purge Units are widely installed on cargo ships, tankers, bulk carriers, offshore vessels, container ships, LPG/LNG carriers, and passenger vessels.

The actual units shown in our stock are professionally inspected by SM MARINE SERVICE™ and are available as quality reconditioned equipment suitable for replacement during dry dock, emergency repairs, or routine maintenance.

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Manufacturer

Nakakita Seisakusho Co., Ltd.

Country of Origin

Japan

Product Type

Marine Pneumatic Air Purge Unit

Marine Applications

• Draft Measurement Systems
• Ballast Tank Monitoring
• Fuel Oil Tank Gauging
• Service Tank Monitoring
• Bilge Tank Monitoring
• Pressure Measurement Systems
• Marine Automation Systems
• Engine Room Instrumentation
• Remote Tank Level Systems

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What Is a Nakakita Air Purge Unit?

An Air Purge Unit is a pneumatic instrument designed to deliver a continuous, low-volume flow of clean compressed air through a sensing tube submerged in liquid. The air pressure required to overcome the liquid head corresponds directly to the liquid level, allowing transmitters or indicators to calculate tank level accurately.

Unlike conventional level sensors placed inside tanks, the air purge method minimizes direct exposure of sensitive instruments to corrosive liquids, sludge, fuel oil, seawater, and chemicals.

Because of this simple yet highly reliable principle, air purge systems remain one of the most trusted level measurement technologies in the marine industry.

SM MARINE SERVICE™ supplies replacement Air Purge Units for vessels requiring dependable marine automation spare parts.

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Working Principle

The Nakakita Air Purge Unit operates using clean, dry compressed air supplied from the ship's instrument air system.

The air passes through:

• Internal pressure regulator
• Flow control mechanism
• Air outlet connection
• Purge tubing
• Pressure sensing line

A continuous stream of air exits the submerged tube inside the tank. The back pressure created by the liquid column is measured and transmitted to the tank gauging instrument. This pressure is proportional to the liquid level, allowing accurate level indication without exposing sensors directly to the liquid.

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Main Features

• Rugged marine construction
• High corrosion resistance
• Stable air flow
• Compact installation
• Long operational life
• Minimal maintenance
• Reliable level measurement
• Excellent repeatability
• Suitable for harsh marine environments
• Compatible with marine automation systems
• Japanese engineering quality
• Easy servicing
• Proven onboard reliability
• Excellent spare parts availability

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Main Components

A typical Nakakita Air Purge Unit consists of:

• Cast aluminum housing
• Air inlet connection
• Air outlet fitting
• Precision pressure regulator
• Needle valve
• Flow control assembly
• Internal filter
• Pressure adjustment mechanism
• Mounting base
• Identification plate
• Inspection port
• Sealing gaskets

Each component is designed for continuous operation in demanding marine engine room environments.

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Marine Applications

Nakakita Air Purge Units are commonly installed in:

• Ballast Tanks
• Fuel Oil Tanks
• Diesel Oil Tanks
• Heavy Fuel Oil Tanks
• Fresh Water Tanks
• Bilge Tanks
• Service Tanks
• Sludge Tanks
• Draft Gauging Systems
• Engine Room Automation
• Pressure Monitoring Systems
• Offshore Platforms
• FPSO Facilities
• Marine Process Systems

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Common Problems & Troubleshooting

No Air Flow

Possible Causes

• Blocked filter
• Air supply failure
• Damaged regulator
• Closed isolation valve

Solution

Inspect the air supply, clean filters, and replace damaged pneumatic components.

Incorrect Tank Level

Possible Causes

• Blocked sensing tube
• Air leakage
• Regulator malfunction
• Pressure transmitter fault

Solution

Check tubing integrity, purge the sensing line, and calibrate associated instruments.

Excessive Air Consumption

Possible Causes

• Loose fittings
• Damaged needle valve
• Internal leakage

Solution

Replace worn seals and tighten pneumatic connections.

Fluctuating Readings

Possible Causes

• Moisture inside tubing
• Unstable air pressure
• Contaminated regulator

Solution

Dry the system and verify the instrument air pressure.

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Maintenance Tips

Regular maintenance significantly improves reliability.

Recommended practices include:

• Inspect air lines weekly.
• Drain moisture from the air system.
• Check pressure settings regularly.
• Replace worn seals.
• Clean internal filters.
• Inspect mounting bolts.
• Test air leakage.
• Verify pressure calibration.
• Keep instrument air dry and oil-free.
• Replace damaged fittings immediately.

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Why Ships Still Use Nakakita Air Purge Units

Although modern radar and ultrasonic level gauges are widely available, the air purge principle remains extremely popular because it is:

• Simple
• Reliable
• Cost-effective
• Easy to maintain
• Highly accurate
• Resistant to contamination
• Suitable for hazardous liquids
• Proven over decades of marine service

Many vessels built in Japan continue to operate with Nakakita Air Purge Units because of their excellent durability and dependable performance.

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Frequently Asked Questions (FAQ)

Is the Nakakita Air Purge Unit still available?

Yes. SM MARINE SERVICE™ supplies both reconditioned and replacement units depending on customer requirements.

Can it be repaired?

Yes. Most units can be overhauled by replacing internal pneumatic components and seals.

Does it require calibration?

Yes. Periodic pressure verification and functional testing are recommended.

Is it suitable for ballast tanks?

Yes. It is widely used in ballast, fuel oil, freshwater, and service tank monitoring systems.

Can SM MARINE SERVICE™ supply spare parts?

Yes. We support worldwide sourcing of marine automation spare parts, repair services, and technical assistance.

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Short Product Description

The Nakakita Air Purge Unit is a high-quality Japanese marine pneumatic device designed for continuous pressure sensing and tank level measurement. Its robust construction, reliable airflow regulation, and long service life make it an ideal solution for marine automation systems installed on commercial vessels worldwide.

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User Manual & Technical Resources

Engineers should refer to:

• Nakakita Air Purge Unit Operation Manual
• Marine Tank Gauging System Manual
• Instrument Air System Maintenance Guide
• Pneumatic Pressure Calibration Procedure
• Ship Automation Maintenance Manual
• Tank Level Measurement Technical Documentation

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SM MARINE SERVICE™

SM MARINE SERVICE™ is a trusted supplier of New and Reconditioned Marine Automation Equipment for vessels worldwide.

We specialize in:

• Marine Automation Systems
• Navigation Equipment
• Engine Room Instrumentation
• Tank Gauging Systems
• Pneumatic Control Equipment
• Repair & Calibration Services
• Spare Parts Sourcing
• Worldwide Export & Technical Support

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Samir Market, DT Road, Pahartali, Beside CDA Market, Chattogram, Bangladesh

China Warehouse & Support Center
Shanghai, China

Website
www.smmarineservice.com

Email
info@smmarineservice.com

WhatsApp
+8801818929292

Marketing Contact
Nazmul Hasan Bhuiyan

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