Does Magnetic Particle Size Matter?

  •  

Breaking down the definitions of particle, micron, and the debate if magnetic particle size has an effect in magnetic particle inspection

By Tim Blasius, Chemical Product Manager

What is a fluorescent magnetic particle?

A fluorescent magnetic particle is a mixture of three elements in which each component serves a particular purpose:

  1. Iron: provides ferrous material to force particle movement when electrically charged by magnetic fields
  2. Fluorescent pigment: what glows brightly underneath ultraviolet lights
  3. Resin: binds these two materials together and keeps them from breaking apart over time, ensuring that fluorescent material does not leak into the bath and cause excess background

Different types of particles are created by altering the properties of a particle by controlling various aspects of these three ingredients. The quality, amount, and blending method can all impact particle performance and characteristics. Magnaflux regulates the proprietary formulas and processes for creating fluorescent magnetic particles to ensure consistently excellent performance in every batch.

 

No magnetic particle product on the market is a single particle size.

Here is an example of one of our products, MG-410, magnified to see the details of the particles. Some areas are pigment (yellow - what makes it glow!), the metallic is iron (what makes it attract to indications), and the resin that holds each piece together. Note that the resulting particles vary in size from small fragments to larger clusters of material.

No magnetic particle product on the market is a single particle size – they all have a range of particle sizes, with some being smaller on average and others being larger on average. Typically, what is reported on product data sheets is the product's mean particle size, but particles can vary widely in size around that mean.

Here is a microscope image of 14A magnified to 400X. Notice the distinct differences between these particles and compare it to MG-410. These differences are not just limited to mean particle size but also particle size distribution, type of iron and fluorescent pigment ingredients, and ratios of pigment / iron / resin. Additionally, the process to create these particles varies as well. All of that in combination results in two particles that both perform excellently, but for often different purposes and applications.

 

How big is a micron?

Mean particle size for magnetic particles is typically a measurement in microns or micrometers. To understand how small these things are, here is an image showing a 6-micron filament lying on top of a human hair. See how thin that filament is? That 6-micron diameter is around the typical mean particle size claimed on most fluorescent magnetic particle datasheets. You can see how small these particles are and how tightly you have to control the process to get even 1-2 micron differences in mean particle size.

This carbon filament is 6 microns in diameter, while it rests on a human hair that is 50 microns thick.

 

Does particle size matter?

Controlling mean particle size is undoubtedly a critical factor in magnetic particle performance; however, it is not the only characteristic that matters. Particle size distribution, quality and quantity of pigment, the ratio of resin used, and quality and quantity of iron are all essential factors that can alter the performance of a fluorescent magnetic particle. Selecting a particle purely based on a mean particle size listed on a product data sheet is unlikely to get you the best performing particle for your application.

We ran some of the top-selling fluorescent magnetic particles on the market through an experiment on a Tool Steel Ring to test this. We magnetized the ring and applied material in the same way for every product and then counted the number of visible indications on the ring for each, per ASTM E1444 standards. We found that particle size has no correlation with performance, and smaller particles don't necessarily get you better results. The chart below shows the resulting data:

Note the R-squared value of 0.0508, which suggests that only ~5% of the variation in Sensitivity is determined by the variation in claimed mean Particle Size. Here we define "Sensitivity" as the number of visible indications on the Tool Steel Ring. It is clear from this chart that, based on our test results, particle size does not determine the performance of fluorescent magnetic particle. Also, note that some of the -performing particles claim to have very small particle sizes (2-3 microns). To check whether differences in how particle size is measured between manufacturers may have skewed our data, we ran the particles on a Horiba Laser Particle Size Distribution Analyzer and plotted that against our Sensitivity data:

Here again, there is no real correlation between the variables based on this data. This suggests that purely selecting products based on particle size will not give you the best performing fluorescent magnetic particle.

 

So, how do I find the fluorescent magnetic particle that is right for me?

Our test data showed that particle size is not the only factor that determines the performance of a fluorescent magnetic particle. But you may be asking, well, if that is the case, how do I find the correct particle for the job?

As we mentioned earlier, many aspects of a particle factor into its performance. Additionally, the importance or impact of those differences can be different depending on the application and types of parts in a test. That is why we recommend that the best way to find the correct particle for the job is to test it on actual parts in application conditions. With so many variables that go into how a particle performs, application testing is truly the preferred method for finding the best match.

 

 

Published January 11, 2022

 


 

Have a question? Please fill out the contact form below. 

Please wait while we gather your results.

Related Blog Articles

4 Reasons to Upgrade Your MPI Wet Bench

4 Reasons to Upgrade Your MPI Wet Bench

To get a new wet bench or maintain the one you have? That is the debate. Learn the four most significant differences between Magnaflux wet benches developed in the 2000s.

How to Calibrate Your MPI Equipment in 5 Steps

How to Calibrate Your MPI Equipment in 5 Steps

In this article, we will go over the five key factors to successfully calibrate your Magnetic Particle Equipment in reference to ASTM E1444, ASTM E3024, ISO 9934, or Nadcap AC7114/2

360° Sprayer on WCP-2 White Contrast Paint Aerosol [Video]

360° Sprayer on WCP-2 and 7HF Aerosols

Apply our product at any angle with the upgraded 360° Sprayer on our WCP-2 White Contrast Paint and 7HF Magnetic Particle aerosol cans

Magnetic Particle Inspection Demo

How to Do Visible Magnetic Particle Inspections

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

New Magnaflux Magnetic Particle Wet Bench for High Speed Inspections

New Magnaflux Magnetic Particle Wet Bench for High Speed Inspections

Universal WE is a multi-directional wet bench designed to meet the speed requirements of high volume production facilities.

Differences of Using Multi-Directional and Uni-Directional

Differences of Using Multi-Directional and Uni-Directional

In this experiment, we compare the speed of a multi-directional magnetic particle wet bench to a traditional uni-directional method.

Lightweight and Heavy Duty Magnetic Particle Inspection Yoke [New Product]

Lightweight and Heavy Duty Magnetic Particle Inspection Yoke

The Y-2 is an AC electromagnetic yoke for magnetic particle inspection that improves inspector productivity through a lightweight, ergonomic design. The Y-2 is the next generation of hand-held yokes that is more robust to survive harsh environments better than its predecessors.

3 Reasons to Try the Y-2 Yoke

3 Reasons to Try the Y-2 Yoke

Explaining mag particle scenarios in the field, and how they can be changed depending on the yoke selection

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

Magnaflux Semi-automated System

Magnetic Particle Equipment for OCTG Couplings

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

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

Mobile Power Packs Demo

Adaptable Mobile Power Packs for Magnetic Particle Inspection

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

Mag Particle Settling Volume Test

Mag Particle Carrier Settling Test Performance

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

Magnetic Particle Equipment Demo

Multi-directional Mag Particle Inspection Equipment

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 Fluorescent Mag Particle Inspections

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

In this article, we explain what a P-Series portable power packs are capable of

3 Ways Magnaflux Improved Power Pack MPI Application

In this article, we explain what a P-Series portable power packs are capable of, and their next generation.

5 Things to Consider When Choosing a Mag Particle Yoke [Checklist]

4 Habits of NDT Aerosol Safe Handling

Safety is a make-or-break factor in a technician's world – we list details around hazards, storage, recycling, and shipping of NDT aerosols

4 Level III Daily Responsibilities

4 Level III Daily Responsibilities

Defining the different types of Level IIIs and some aspects of what their job entails

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.

5 Things to Consider When Choosing a Mag Particle Yoke [Checklist]

5 Things to Consider When Choosing a Mag Particle Yoke [Checklist]

In this article we outline some key factors to consider when selecting the right electromagnetic yoke or contour probe for magnetic particle testing

5-Point Guide to Yoke Best Practices

5-Point Guide to Yoke Best Practices

Learn how daily checks and maintenance can improve the lifespan of a yoke for a safer work environment

We explain why each Magnetic Particle Inspection accessory is needed to validate MPI systems

8 System Performance Tools for Magnetic Particle Inspection

In this article, we list and explain why each Magnetic Particle Inspection accessory is needed to validate the system performance of an inspection

In this article, we review the Nadcap requirements for proper magnetization

9 Magnetic Particle Technique Requirements to Document for Nadcap [Checklist]

In this article, we review the Nadcap requirements for proper magnetization and the importance of documentation for auditors

Understand the difference between magnetic particle inspection standards ASTM E709, ASTM E1444 and A

A Guide to ASTM E3024 Standard Practice for Magnetic Particle for General Industry

Understand the difference between magnetic particle inspection standards ASTM E709, ASTM E1444 and ASTM E3024

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.

A Primer on System Performance Checks for High Volume NDT Inspections

This article explores a few of the approaches most Magnetic Particle Inspectors practice to check their system performance at regular intervals

ASTM E1444: Key Changes and Updates

ASTM E1444: Key Changes and Updates

The next revision of ASTM E1444 is out for the final ballot, and a lot is changing. Here are five significant changes that you should know about for 2021.

Breaking Down How to Use Magnetic Flux Indicators and QQIs

Breaking Down How to Use Magnetic Flux Indicators and QQIs

In this article, Magnetic Particle Inspection Flux Indicator Strips and Quantitative Quality Indicators (QQI) are defined and given a user manual approach to find artificial flaw standards

Carrier II Comparison to Water Baths Effect on Mag Particle Wet Bench Lifespan [Case Study]

Carrier II Comparison to Water Baths Effect on Mag Particle Wet Bench Lifespan [Case Study]

A brief overview of the 4 advantages of using a petroleum suspension vehicle bath to protect your magnetic particle wet bench investment.

Does Magnetic Particle Size Matter?

Does Magnetic Particle Size Matter?

Breaking down the definitions of particle, micron, and the debate if magnetic particle size has an effect in magnetic particle inspection

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

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.

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

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.

Importance of Using Magnaflux Authorized Service Centers

Importance of Using Magnaflux Authorized Service Centers

Explaining the who, what, when, where, why, and how of Authorized Service Centers, and why they are best for NDT maintenance and repairs

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

Magnetic Field Safety Guidelines for Pacemakers

Magnetic Field Safety Guidelines for Pacemakers

This article reviews the limitations of operators with cardiac pacemaker’s exposure to magnetic particle inspection equipment.

Customized Solutions for Unique Needs

Magnetic Particle Equipment – Customized Solutions for Unique Needs

In this article, we show two examples how Magnaflux can customize magnetic particle equipment

Use the ROI Calculator to learn how multi-directional magnetic particle equipment can save

Magnetic Wet Bench Saves $75,833 a Year with Improved Speed and Efficiency [Case Study]

Use the Universal WE ROI Calculator to learn how multi-directional magnetic particle equipment can save you time and money

Multidirectional Magnetization for Magnetic Particle Inspection

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

Overview of Liquid Penetrant Inspection and Magnetic Particle Inspection Specifications

Overview of Liquid Penetrant Inspection and Magnetic Particle Inspection Specifications

Understanding ASTM and SAE/AMS specifications to select the corresponding Magnaflux product for Liquid Penetrant and Magnetic Particle Inspections

Proactive Ergonomics for MT Field Inspection

Proactive Ergonomics for MT Field Inspection Can Improve Your Bottom Line [SlideShare]

Learn about the most effective risk-reduction measure to increase safety for field inspectors

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

System Performance Check for Mag Particle Benches

System Performance Check for Mag Particle Benches

According to ASTM E1444 and ASTM E3024 daily system performance checks are required. This article explains how to perform those checks.

Understanding Safety Data Sheets

Understanding Safety Data Sheets: Do You Know What’s in the Chemicals You Handle?

We highlight the 5 major sections to understand on a Safety Data Sheets (SDS) in accordance with US OHSHA Hazcom 2012 GHS regulations

Understanding the Magnaflux Shelf Life Statement for NDT Chemicals

Understanding the Magnaflux Shelf Life Statement for NDT Chemicals

Answering popular questions regarding shelf life for magnetic particle and liquid penetrant products used in nondestructive testing

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.

What You Need to Start-up In-house Testing [Checklist]

What You Need to Start-up In-house Testing [Checklist]

Step-by-step process listing everything from the equipment needed in magnetic particle testing and liquid penetrant testing to preparation for NDT audits

Magnetic Particle Inspection Demo

Y-2 AC Electromagnetic Yoke for Non-destructive Testing

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

JOIN OUR MAILING LIST TO RECEIVE THE LATEST NDT INSIGHTS AND ARTICLES FROM MAGNAFLUX

Magnaflux

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

Select Your Country North America Mexico Brazil China Europe Russia India New Zealand, Australia, Japan, Southeast Asia
© 2021 Magnaflux - all rights reserved.
top

We have placed cookies on your computer to give you the best possible experience with our website. These cookies are also used to ensure we show you advertising that is relevant to you. If you continue without changing your settings, you are agreeing to our use of cookies to improve your user experience. You can click the cookie settings link on our website to change your cookie settings at any time.