Inspectioneering

Magnetic Particle Testing (MPT)

Magnetic Particle Testing (MPT), also referred to as Magnetic Particle Inspection, is a nondestructive examination (NDE) technique used to detect surface and slightly subsurface flaws in most ferromagnetic materials such as iron, nickel, and cobalt, and some of their alloys. Because it does not necessitate the degree of surface preparation required by other nondestructive test methods, conducting MPT is relatively fast and easy. This has made it one of the more commonly utilized NDE techniques.

MPT is a fairly simple process with two variations: Wet Magnetic Particle Testing (WMPT) and Dry Magnetic Particle Testing (DMPT). In either one, the process begins by running a magnetic current through the component. Any cracks or defects in the material will interrupt the flow of current and will cause magnetism to spread out from them. This will create a “flux leakage field” at the site of the damage.

The second step involves spreading metal particles over the component. If there are any flaws on or near the surface, the flux leakage field will draw the particles to the damage site. This provides a visible indication of the approximate size and shape of the flaw.

There are several benefits of MPT compared to other NDE methods. It is highly portable, generally inexpensive, and does not need a stringent pre-cleaning operation. MPT is also one of the best options for detecting fine, shallow surface cracks. It is fast, easy, and will work through thin coatings. Finally, there are few limitations regarding the size/shape of test specimens.

Despite its strengths, the method is not without its limits. The material must be ferromagnetic. Likewise, the orientation and strength of the magnetic field is critical. The method only detects surface and near-to-surface defects. Those further down require alternative methods. Large currents are sometimes required to perform this method, thus “burning” of test parts is sometimes possible. In addition, once MPT has been completed, the component must be demagnetized, which can sometimes be difficult.

 

Related Topics

Acoustic Emission Testing (AET) Advanced Ultrasonic Backscatter Technique (AUBT) Eddy Current Array (ECA) Electro Magnetic Acoustic Transducers (EMAT) Guided Wave Ultrasonics (GWUT) Infrared Thermography (IT) Infrared Thermometry Liquid Penetrant Examination (LPE) Magnetic Flux Leakage (MFL) Meandering Winding Magnetometer Array (MWMA) Pulse Reflectometry Pulsed Eddy Current (PEC) Radiography Thermography Ultrasonic Testing (UT)

STAY INFORMED WITH RELEVANT INDUSTRY CONTENT

Join 10,000+ subscribers and receive weekly updates on industry content, news, and events straight to your inbox. Enter your information below:

Articles
  • September/October 2016 Inspectioneering Journal
    By Kimberley Hayes at Olympus

    Detecting, quantifying, and sizing indications characterized as a “crack” in critical equipment have long been the global benchmark of asset integrity programs. Therefore, the increased precision that inspection programs obtain using advanced technologies can dynamically improve the overall assessment.

  • Blog
    June 1, 2015 By Nick Schmoyer at Inspectioneering

    Nondestructive Testing (NDT) makes up the majority of testing performed in our industry. There many different types of nondestructive testing techniques. Each method has its own advantages and disadvantages; each can detect different types of flaws. Some are simple to perform, others are difficult. Some are used on several different types of equipment, others are more restricted.

  • September/October 2014 Inspectioneering Journal
    By Ana Benz at IRISNDT, Dr. Donald H. Timbres at D. & E. Consulting, Inc. , and Matt Stroh

    A small leak from top tubesheet-to-tube welds prompted further inspection of the 1¼Cr- ½Mo Ammonia Converter Boiler Feed Water (BFW) Exchanger during a planned shutdown. Further cracks were identified in the top channel to tubesheet butt weld that operated at 700 °F.

  • January/February 2014 Inspectioneering Journal
    By Marc McConnell, P.E. at Versa Integrity Group, Josh Yoakam at Holly Refining and Marketing - Tulsa, LLC, and Frank Dean at Ion Science, Ltd.

    This is the second of two articles published in Inspectioneering Journal discussing the value of hydrogen bake-outs. Our first article was published in the May/June 2013 issue and received a great response from the Inspectioneering community. In this piece, we will continue the discussion and touch on some new technologies used to enhance the bake-out process.

  • May/June 2012 Inspectioneering Journal
    By Jason Butz at SAIT Polytechnic

    Over the past 100 years, Nondestructive testing has made tremendous advances. New NDT methods have been introduced, while old "tried and true" methods continue to be improved. Although some NDT methods have drastically changed or "evolved" over time, the principle behind each method has remained the same; "To ensure the safety and integrity of manufactured items or goods."

  • Partner Content

    Facilities are facing increasing challenges, including justifying inflated budgets, managing contractor hours, ensuring regulatory compliance and qualifying the work being completed. To help facilities manage evolving inspection requirements, PinnacleART offers Fixed-Price Inspection (FPI), meaning we will develop and execute a comprehensive Risk-Based Inspection plan for one fixed-price. Yes, you read that right – one fixed-price.

  • September/October 2004 Inspectioneering Journal
    By Greg Alvarado at Inspectioneering Journal

    Exactly two years ago, an interview with John Nyholt appeared in the “IJ”. New ground will be covered in this interchange. We at the IJ thought it might be valuable to spend some time chatting about his background, challenges he has faced recently and what he feels are some of the biggest challenges ahead for the Inspectioneering® community.

    Videos
      White Papers
        Downloads & Resources
          Events
            Related News

              Inspectioneering Journal

              Explore over 20 years of articles written by our team of subject matter experts.

              Company Directory

              Find relevant products, services, and technologies.

              Job Postings

              Discover job opportunities that match your skillset.

              Case Studies

              Learn from the experience of others in the industry.

              Event Calendar

              Find upcoming conferences, training sessions, online events, and more.

              Industry News

              Stay up-to-date with the latest inspection and asset integrity management news.

              Blog

              Read short articles and insights authored by industry experts.

              Asset Intelligence Reports

              Download brief primers on various asset integrity management topics.

              Videos

              Watch educational and informative videos directly related to your profession.

              Expert Interviews

              Inspectioneering's archive of interviews with industry subject matter experts.