Magnetic Particle Testing -VII: Magnetic Particle Testing Equipment.

Magnetic Particle Testing Equipment.

The following should be considered when selecting Magnetic Particle Testing

1. Is Equipment for Wet or Dry method.
2. Magnetization requirement.
3. Demagnetization- Incorporated or separated unit?
4. Amperage Required.
5. Line Voltage Requirements.
6. Accessories Needed or Required.

Wet Horizontal Equipment

To obtain Circular Magnetization, the specimen is clamped between the Head and Tail Stocks.

For Longitudinal Magnetization, the coil is moved so that the area to be tested is encircled by the coil.

A typical Wet Horizontal Unit usually accommodates both AC and HWDC Magnetization.  The Wet continuous field method has three basic steps;

1. Flow bath through nozzle and over entire surface of part.
2. Stop bath flow.
3. Apply current at the instant bath flow is stopped. 
   

 

Dry continuous-field method

With this method the powder is usually applied from a shaker, bulb, or blower and follows these steps:

1. Apply magnetizing current
2. Blow powder particles over magnetized area.
3. Blow excess powder off part.
4. Shut off magnetizing current.

The powder should float to the magnetized area so the particles will be attracted to any flux leakages. The dry powder method is typically used with both mobile and portable equipment which will be discussed on the following.

Mobile Equipment

In many cases it is necessary to bring the equipment to the specimen.

Typical Mobile Equipment

 Typical Mobile Equipment such as the one above usually operates on 220/440 volts AC and will produce about 4000 amperes. Mobile equipment will usually produce both AC & HWDC magnetizing current.

The Cables used on the above vary from 15 feet to 100 feet. Shorter cable will permit the maximum current output.

Prods and Cables are usually used with the mobile equipment. It often takes two technicians to manipulate the Prods & apply the magnetic powder.

However, Longitudinal Magnetization can be produced by wrapping the cable into a coil. It is also possible to use a central conductor clamped between the two cables to produce Circular Magnetization.

Typical Mobile equipment uses the Dry Powder Method but can be use with Aerosol cans or External Tanks.

 

Portable Equipment

Portable Equipment is lighter and less expensive than the other types of magnetic particle testing equipment.

Typical Portable Equipment

 Typical Portable Equipment as shows above operates on 110/200 volts AC with an output of between 500 & 1200 amperes. These units usually have a choice of either AC or HWDC.

As with mobile equipment, the cables can be used for prods, wrapping into a coil or connecting to a central conductor.

Portable Equipment also used the Dry Powder Method for most application.

Demagnetizing Equipment

The most common type of Demagnetizing Equipment consists of an open coil through which AC is flowing.

A typical unit is shows below and includes a track that will carry the part through the coil. As the part is carried away from the coil the magnetic field is reduced. The continuously AC current in the coil completes the demagnetization.

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Magnetic Particle Testing