Frequently Asked Questions About NDT Carrier Fluid


Learn what an NDT-approved carrier is, and what sets it apart from commonly used, non-approved base oils such as Isopar M or kerosene 

August 15, 2017  |  by Cheri Stockhausen, Product Applications Manager

Magnaflux Carrier II Application


Many people, even some NDT experts, do not realize what an important role NDT carrier fluid plays in the performance and dependability of a magnetic particle inspection. 

In this article, we explain what an NDT-approved carrier is and what sets it apart from commonly used, non-approved base oils.


What is an NDT carrier fluid?

An NDT carrier fluid is the fluid in which fluorescent and nonfluorescent magnetic particles are suspended to facilitate their application.

Also known as a petroleum-base suspension vehicle.


What makes an oil carrier categorized as NDT material?

  • An NDT-approved carrier is a light petroleum distillate that imparts magnetic particle suspension stability and mobility.

  • It is virtually non-fluorescent so it will not interfere with the detectability of fluorescent magnetic particle indications.

  • NDT-approved carrier oil prevents corrosion of most alloy parts, and prevents corrosion of equipment components in magnetic particle testing machines.

  • Viscosity promotes good magnetic particle movement. Per ASTM E709 Standard Guide for Magnetic Particle Testing, the viscosity of an NDT-approved carrier vehicle should not be higher than 3.0 cSt at 100°F / 38°C and not more than 5.0 cSt at the lowest temperature the carrier is used at.


What makes an NDT carrier fluid different from a non-NDT petroleum-base oil like kerosene or Isopar M?

A NDT Carrier fluid is:

  • Very low odor: for operator safety and comfort

  • Nonfluorescent: so oil does not produce excessive fluorescent background that will interfere with fluorescent indications formed by fluorescent particles

  • High flash point: for safety

  • Low viscosity: less than 5 centistokes for proper particle mobility and indication formation


What is the safe zone a carrier’s flash point should be within?

NDT carrier fluid should have a flash point above 200°F / 93.3°C. This high flash point is safe for use in most facilities, while promoting a safe work environment for NDT operators.

Why is it important to have a high flash point?

A high flash point improves operator and plant safety, and helps prevent fires. OSHA typically requires a flash point at or above 200°F / 93.3°C for fluids that are used in open tanks. 

What are the dangers of using an oil with a lower flash point?

  • Fire

  • Damage to the mag particle testing equipment

  • Injury to operators

  • Down time

  • Costly repairs and replacement


What are dangers of not using an NDT-approved carrier?

  • Less inspection reliability: Fluorescent carrier oil may interfere with inspection

  • Poor particle mobility: Viscous (above 3.0 cSt at 100°F / 38°C) carrier oil will impede particle mobility and formation of indications

  • Clumping of magnetic particles: NDT carrier fluid offers good magnetic particle suspension stability and good particle mobility which enhances indication detection

  • Corrosion of your magnetic particle unit: Using a NDT carrier fluid will protect equipment components on the mag particle unit from corrosion, leading to less maintenance and repair of the mag particle equipment and lower maintenance and repair costs. MPI units that use NDT carrier fluid look virtually new even after several years of use

  • Higher background fluorescence: Difficult inspection (fluorescent indications formed by fluorescent magnetic particles will not jump out against strong fluorescent background)

  • Low flash point: Low flash point oils are unsafe. Fires can happen when using low flash point oils. Low flash point oils are not safe for the NDT operators.

  • Poor working conditions for operators: Strong odors, flammable oils (fire, safety), difficult inspection due to excessive fluorescent background caused by fluorescent oil



Do you have a story about how a non-NDT-approved carrier impacted an inspection?
Share your knowledge in the comments section below.

Subscribe to Magnaflux News:

Want to stay up on the latest NDT insights and articles from Magnaflux? 

Subscribe to Magnaflux updates above to get fresh news delivered to your inbox once a week.

Please wait while we gather your results.

Related Blog Entries

The most common incorrect assumptions about magnetic particle inspection

10 Misunderstandings about Magnetic Particle Testing

This article discusses the most common incorrect assumptions about magnetic particle inspection and gives you some solutions to combat these misunderstandings


A Primer on Magnetic Particle Inspection

A Primer on Magnetic Particle Inspection [SlideShare]

A 4-minute mag particle primer to help you understand why this simple, quick, and effective method is still widely used today.


Why carrier oil is a critical part of the MPI process

Importance of Using the Correct Oil for Magnetic Particle Inspection

In this article, we explain why carrier oil is a critical part of the MPI process and which characteristics to look for when choosing an NDT carrier fluid


Carrier II SlideShare

Understanding Wet Method Magnetic Particle Testing Carrier II [SlideShare]

Learn about Magnaflux's NDT-approved petroleum base suspension vehicle for Wet Method Magnetic Particle Testing, and how it compares to competitors.


Technique Management Challenges

How Integrated Techniques Can Ease the Pain of Part Variability

This article explores issues many magnetic particle inspection operators face when testing diverse parts that require specific standards and acceptance criteria in a world that does not accept mistakes


Magnaflux Semi-automated System

Magnetic Particle Equipment for OCTG Couplings [Video]

See how Magnaflux's semi-automated magnetic particle testing system simplifies Oil Country Tubular Good coupling inspection.


Magnaflux Database System for NDT Control

Database System for Mag Particle Wet Benches [Video]

Learn how this process-control and efficiency upgrade for mag particle testing helps NDT pros improve quality with less time.


Magnetic Particle Crack Comparison

How Brightness and Contrast Impact NDT Inspections

How perception and vision can have a significant impact on probability of detection in non-destructive testing inspections.


Mobile Power Packs Demo

Adaptable Mobile Power Packs for Magnetic Particle Inspection [Video]

Learn how to use M-Series magnetizing equipment to perform Magnetic Particle Inspections on a variety of large, heavy parts.


NDT Carrier Oil Fluid for Mag Particle Testing

Frequently Asked Questions About NDT Carrier Fluid

In this article, we explain what an NDT-approved carrier is and what sets it apart from commonly used, non-approved base oils


Mag Particle Settling Volume Test

Mag Particle Carrier Settling Test Performance [Video]

See how three common magnetic particle testing carriers perform in a standard ASTM E1444 settling volume test.


Aerospace MRO NDT

Reducing Particle Loss During Mag Particle Testing [Case Study]

In this case study, we help an aerospace MRO customer resolve fluctuations in their magnetic particle concentration


Magnetic Particle Inspection Demo

5 Quick Tips for Mag Particle Testing [Infographic]

Some handy tips for beginners who are new to magnetic particle testing or NDT pros who want an easy reference guide.


Magnetic Particle Equipment Demo

Multi-directional Mag Particle Inspection Equipment [Video]

Watch the versatile MD-Series multi-directional mag particle inspection equipment in action. Learn how this wet bench can help you save time and money.


Magnetic Particle Inspection Demo

How to Do Visible Magnetic Particle Inspections [Video]

See an overview of visible, dry-method magnetic particle inspection method according to ASTM E1444.


Magnetic Particle Inspection Demo

How to Do Fluorescent Mag Particle Inspections [Video]

Watch a demonstration of the magnetic particle inspection method according to ASTM E1444 with basic steps for NDT using fluorescent magnetic particles.


How to Do Preventative Maintenance for Magnetic Particle Equipment

Read how regular upkeep on mag particle equipment is critical for non-destructive testing to safe guard inspections & reduce downtime.


Multidirectional Magnetization for Magnetic Particle Inspection

Learn about multi-directional magnetization applications and how mag particle inspections can benefit from multi-vector magnetization.


The following required items were not provided or are in the wrong format. Please provide the required responses and submit again:

  Please enter your name
  Please enter a valid email
Comment Title
Comment: 250 characters left
  Please enter a comment

Subscribe to Magnaflux News:


155 Harlem Avenue
Glenview, IL 60025, USA
Telephone: +1 847-657-5300
Fax: +1 847-657-5388
Contact Magnaflux Customer Service

Select Your Country North America Mexico Brazil China Europe Russia India New Zealand, Australia, Japan, Southeast Asia
© 2016 Magnaflux - all rights reserved.