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NAKAKITA SEISAKUSHO NS-967F AIR PURGE UNIT – Complete Technical Guide for Marine Draft Gauge & Tank Level Measurement Systems

Posted onJune 13, 2026

Introduction

The NAKAKITA SEISAKUSHO NS-967F Air Purge Unit is a critical component used in marine draft gauge and tank level measurement systems onboard commercial vessels. Designed and manufactured by Japan's renowned Nakakita Seisakusho, the NS-967F provides reliable pneumatic pressure generation for accurate draft and tank level monitoring.

These units are widely installed on bulk carriers, tankers, container vessels, LPG/LNG carriers, offshore support vessels, and other commercial ships where precise draft measurements are essential for navigation safety and cargo management.


NAKAKITA NS-967F Air Purge Unit

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What is the NS-967F Air Purge Unit?

The NS-967F Air Purge Unit is a pneumatic device that continuously supplies compressed air into draft measuring pipes or tank sounding pipes.

By maintaining a constant airflow, the system measures the hydrostatic pressure exerted by seawater or liquid inside a tank. This pressure is then converted into draft or level readings displayed on bridge indicators and cargo monitoring systems.

The technology is simple, reliable, and highly accurate, making it one of the most trusted methods for marine draft measurement.


Main Functions of the NS-967F

Continuous Air Supply

Maintains a steady airflow through draft sensing lines.

Draft Measurement Support

Provides pressure reference for draft gauge systems.

Tank Level Monitoring

Used in ballast and service tank measurement systems.

Pressure Stabilization

Ensures accurate hydrostatic pressure measurement.

Marine Automation Integration

Works with vessel monitoring and automation systems.


Working Principle

The NS-967F operates using the well-established pneumatic bubbling principle.

Step 1

Compressed air enters the Air Purge Unit.

Step 2

The unit regulates airflow and pressure.

Step 3

Air is sent through sensing tubes installed below the waterline or inside tanks.

Step 4

Air bubbles exit from the tube opening.

Step 5

The pressure required to release the bubbles corresponds to the liquid height.

Step 6

Pressure signals are transmitted to draft indicators and monitoring systems.

Step 7

The bridge receives accurate draft or tank level readings.


Marine Draft Measurement Applications

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Key Features

High Reliability

Designed for continuous operation in harsh marine environments.

Japanese Engineering

Manufactured by NAKAKITA SEISAKUSHO of Japan.

Long Service Life

Robust construction ensures years of reliable service.

Corrosion Resistance

Suitable for marine engine room and cargo environments.

Easy Installation

Simple integration with existing draft gauge systems.

Low Maintenance

Requires minimal servicing when operated correctly.

Stable Air Output

Provides accurate measurement results.


Applications on Ships

The NS-967F Air Purge Unit is commonly used on:

Bulk Carriers

Draft monitoring during cargo loading and unloading.

Oil Tankers

Ballast and cargo level measurement.

Chemical Tankers

Tank level monitoring systems.

Container Vessels

Draft indication and ballast management.

Offshore Vessels

Marine tank monitoring systems.

General Cargo Ships

Hydrostatic pressure measurement applications.


Importance of Draft Measurement

Accurate draft measurement is essential because it helps operators:

  • Prevent overloading
  • Ensure safe navigation
  • Comply with SOLAS regulations
  • Monitor ballast conditions
  • Improve fuel efficiency
  • Optimize cargo operations
  • Maintain vessel stability

Typical Draft Gauge Installation

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Main Components Associated with NS-967F

A complete draft measurement system may include:

Air Purge Unit

NS-967F

Draft Sensors

Pressure Transmitters

Draft Indicators

Tank Level Displays

Monitoring Controllers

Pneumatic Tubing

Junction Boxes


Common Problems and Troubleshooting

No Draft Reading

Possible Causes

  • Air supply failure
  • Blocked tubing
  • Internal valve malfunction

Solution

  • Check air source
  • Inspect tubing
  • Verify purge operation

Unstable Reading

Possible Causes

  • Water ingress
  • Air leakage
  • Damaged tubing

Solution

  • Check piping integrity
  • Replace damaged components
  • Verify pressure stability

Low Air Flow

Possible Causes

  • Blocked filter
  • Regulator issue
  • Internal contamination

Solution

  • Clean filters
  • Inspect regulator
  • Service purge unit

Maintenance Guidelines

Monthly

  • Visual inspection
  • Leak checking

Quarterly

  • Air pressure verification
  • Tubing inspection

Annually

  • Complete functional testing
  • Internal cleaning
  • Calibration verification

Proper maintenance significantly increases service life and measurement accuracy.


Advantages of the NS-967F System

Compared with alternative technologies, the NS-967F offers:

  • Proven pneumatic technology
  • High reliability
  • Easy maintenance
  • Long operating life
  • Accurate measurement
  • Low operating cost
  • Global service acceptance
  • Marine industry approval

Marine Tank & Draft Monitoring Systems

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Frequently Asked Questions (FAQ)

What does the NS-967F Air Purge Unit do?

It supplies regulated air for draft and tank level measurement systems.

Is it used only for draft gauges?

No. It can also be used in tank level monitoring applications.

Which ships use NS-967F?

Bulk carriers, tankers, container ships, offshore vessels, and general cargo ships.

Is calibration required?

Periodic verification is recommended to maintain accuracy.

Can it be integrated with automation systems?

Yes. It can work alongside various marine monitoring and automation systems.


Available Documentation

Typical documentation includes:

User Manual

  • Installation Instructions
  • Operating Procedures
  • Safety Information

Technical Manual

  • Pneumatic Diagrams
  • Specifications
  • Maintenance Procedures

Service Documents

  • Spare Parts List
  • Troubleshooting Guide
  • Calibration Instructions

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Available Condition

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