• Non-destructive testing・Printing and marking

How to apply magnetic particles to test objects

In magnetic particle testings, it is important to spray (apply) magnetic particles on the testing surface evenly so that magnetic particles are adsorbed in flaws.
It is necessary to determine appropriate applying method of magnetic particles depending on the test object and inspecting environment.

How to apply magnetic particles

Applying methods are mainly divided into “wet method” and “dry method”.

Wet method

Prepare and use the inspection liquid (magnetic particle liquid) in which magnetic particles have been dispersed.

• It is possible to apply magnetic particles evenly on testing surfaces with complicated shapes, and it is easy to grasp the applying condition.
• Testing operation is easy and test results tend to be stable.
• It is necessary to regularly manage the condition and performance of the inspection liquid (magnetic particle liquid).
• Post-processing according to the dispersion medium is necessary as the test object gets wet with liquid.

Dry method

Use magnetic particles as powder itself

• It is possible to inspect parts with high temperature such as welding groove surface and to test objects for which getting wet with liquid is unfavorable.
• Sensitivity to a flaw inside the test object is relatively high.
• As it is a powder, test conditions are hard to stabilize and results tend to vary.
• Unsuitable for detailed inspections and test objects with complicated shapes.

Types of wet method

In “wet method”, it may be possible to improve efficiency and accuracy of testing by selecting a liquid for dispersing magnetic particles that is suitable to the contents of the test.

“Water dispersion” using water

A method often adopted for its easiness in procurement, cost, and safeness.
It is necessary to beware of the occurrence of rust on the test object, as water is used.

“Oil dispersion” using liquid oil such as kerosene

No rust occurs on the test object.
It is necessary to manage the Fire Service Law, etc. as flammable liquid is used.

Preparation of inspection liquid (magnetic particle liquid)

In the magnetic particle testing with wet method, the condition of inspection liquid (magnetic particle liquid) affects the test result greatly.

Especially the amount of magnetic particles (concentration of magnetic particle liquid) contained in the inspection liquid is important, and the concentration of magnetic particle liquid suitable for the testing varies by test objects, flaws intended to be detected, types of magnetic particles applied, etc.

It is recommended that customers check and manage the range of concentration of the magnetic particle liquid that can generate valid inspection results.
Also, it is important to get magnetic particles dispersed evenly in the inspection liquid.
When preparing the inspection liquid of water dispersion type with which magnetic particles are likely to create lumps, please refer to the following in preparation of the inspection liquid.

Inspection liquid preparation method for magnetic particles in powder type (Super Magna LY-10 to 40, etc.)

In the case of magnetic particles in powder + liquid-type dispersant (BC-700, EC-4, etc.)

• Measure the powder and dispersant, each in a small container.
  Slowly add the dispersant into the magnetic particles, and knead well to form a paste.
• Add the pastelittle by little while stirring waterin the tank.
• Wash thepastestuck inside the small container with waterin the tankand put it in the tank.
• After 5 to 10 minutes,confirmsuspensionof the inspection liquid, and start testing.

Preparation method for the inspection liquid of concentrated magnetic particle liquid type (Conc.) (Eco Magna LY-10 to 40 Conc.)

• Shake the container of Eco Magna LY-Conc.well up and down andmeasure it in a smallcontainer.
• AddEco-Magna LY-Conc.while stirring water in the tank.
  (Wash LY-Conc.stuck inside the small containerwith waterin the tank and put it in the tank)
• After 5 to 10 minutes, confirm suspension of the inspection liquid, and start testing.
  

* When preparing the inspection liquid with LY-Conc., please refer to the table below and put in the amountaccording to the concentration of the magnetic particle liquid.

<Example of preparation of inspection liquid (in the case of 100 L)>