non-destructive examination

CISR2 offers several methods of non-destructive examination to measure thickness of metal plate and examine welded joints during fabrication and after a working time period of equipment (usually once every six years)

Non-destructive examination (NDT) is technical term describing examinations that allows to examine and detect of metal structure and welded joints without destruction of examined entities.

Most popular method NDT are :

1. Ultrasonic test – UT.

2. Radiographic test – RT.

3. Penetrant test-PT.

4. Magnetic particle test – MT.

The first and the second ones are used to detect defects inside a metal wall; third and fourth - surface defects. You can find more technical details here.

1. Ultrasonic test

UT is the most popular and low cost method. A ray of ultrasound is transmitted through metal structure. Reflected ray from surface of defect and boundary is recorded. By analyzing this signals, we can retrieve size and position of defect as well as thickness of metal plate.

With equipment of newest generation in Vietnam and competent technicians, CISR2 have overwhelm advantage in ultrasonic examination.

2. Radiography test

As being named, in this method, metal structure is photographed with X-ray or gamma ray. Because these rays can transmit through the structure, not only surface but the structure itself also is recorded on film. While result of UT much depends on experience of the technician and his recording, RT result is an image and can be analyzed, discussed by some technicians and stored for later use.

The disadvantage is that RT involves radio hazard and high cost.

CISR2 can now offer fastest and most reliable RT with reasonable price.

3. PENETRANT TEST (PT):

One of the most popular methods to detect surface cracks of metal structures and welded joins is penetrant test, specially for non-magnetized material. In this method, the dying liquid is prayed on the tested surface. This liquid is well penetrating. If there is crack on surface, the liquid can penetrate through and stay event in the smallest crack which can not be visible for human eyes. After waiting several minutes, the dying liquid will be removed and the second liquid (developer) is prayed on the tested surface. This one will show color (usually red) on the surface where the first liquid stays in the crack.

To apply this test, the tested surface must be very clean, dry and smooth. This method is not suitable for rough surface. Although, PT does not require expensive equipment, it depends much on the person who do these test. This person must be trained and have adequate experience.

CISR2 usually uses PT as a additional test to detect cracks on the welding joins and structures of cranes ...ect

4. MAGNETIC PARTICLE TEST (MT):

Although MT can't be applied for non-magnetized materials such as stainless steels, it has higher reliability and sensibility than PT. Furthermore, tested surface is not required clean and smooth.

In this method, magnetic powder is prayed on tested surface while this surface is magnetized by two magnetic poles. If there is no crack on the surface, magnetic powder distributes along line of magnetic force. Otherwise, powder concentrate in cracks due to interruption of line of magnetic force. By analyzing the distribution of magnetic powder, any defects on the surface can be detected. In fact, a white substance is prayed as background contrasting dark magnetic powder. Sometime, ultraviolet light is used to increase sensibility.

CISR2 uses MT to examine boiler and pressure vessel which have high risk of crack after a period of working time such as ammoniac stored tanks, clocking mechanic of PV with quick opening closure, de-aerator, steam drum of boiler...etc. Besides, we also use MT as additional test for welding joins and entities after heat treatment.