The methods of magnetic particle testing

Magnetic particle testing (MT),also known as magnetic particle inspection(MPI),is a nondestructive inspection method.Magnetic particle testing is a method of observing defects by using magnetic powder as display medium.According to the type of magnetic powder medium applied during magnetization,the detection methods can be divided into wet and dry methods.

Magnetic particle testing for large diameter elbow welds

Magnetic powder suspension in oil,water or other liquid medium is called wet method.It distributes magnetic suspension evenly on the surface of the work piece in the detection process,and shows the shape and size of the defect by using the fluid flow and magnetic leakage field to attract magnetic powder.In wet test,due to the dispersion of magnetic suspension and suspension performance,the magnetic powder particles can be used are smaller.Therefore,it has high detection sensitivity.It is especially suitable for detecting small surface defects,such as fatigue cracks and grinding cracks.Wet process is often used in conjunction with fixed equipment,as well as mobile and portable equipment. The magnetic suspension used in wet process can be recycled.

Dry method is called dry powder method. In some special cases,wet method cannot be used to detect,but special dry magnetic powder is directly applied to the magnetized work piece according to the program.The defects of the work piece show magnetic marks.Dry inspection is mostly used for local inspection of large castings,forgings,large structural parts and weld it is usually used in conjunction with portable equipment.

large diameter elbow after magnetic particle testing

Advantages of magnetic particle inspection:

Magnetic particle inspection can only be used to detect defects on the surface or near the surface of ferromagnetic materials.Because the discontinuous magnetic traces accumulate on the detected surface,the discontinuous shape,position and size can be visually displayed,and its properties can be roughly determined.This method is simple and convenient,low detection cost,high sensitivity to surface and near surface defects of ferromagnetic materials,is the preferred method for surface defect detection.

Haihao Group manufacture flange products more than 30 years,our quality inspection department can carry out the magnetic particle testing as per clients requirement.If you have any questions,please email us:sales@haihaogroup.com