Ultrasonic flaw detectors: instructions, diagram, characteristics, manufacturers, verification

The study of physical bodies by ultrasonic waves began to be introduced at the beginning of the last century. The measuring instrument was called the "ultrasonic flaw detector". Immediately after the discovery, the method took on a wide popularity among engineers and people involved in research.

General information about the machine

Ultrasound penetrates through the layers of solid material and can fix even the presence of a tiny crack located in the interior of the object. The device allows to determine the defect at a depth of 7-50 mm with an accuracy of ± 1 mm.

Ultrasonic flaw detectors have different levels of sensitivity. Such an indicator is determined by the small size of the defects. The scope of use of aggregates is very wide. For example, the production of metals.

A clear interface of the device ensures an efficient and unified use of the device. The device is distinguished by its accuracy, which makes it possible to obtain a high-level result and to detect the present defects.

Fields of application

Ultrasound-based ultrasonic flaw detection can be applied to almost any building material to detect the presence of hidden cracks, pores, slags and other flaws.

The most common areas include:

• Welding seams. This is the main application area of the unit.
• Primary metals in bridge beams, uneven bars, rods, pipe billets.
• Infrastructure. Bolted connections, rails for trains, metal structures.
• Petrochemical industry. Inspection of pipelines of tanks, load-bearing structures.
• Monitoring the operation of wheels and shafts of train wagons, aircraft chassis, engine suspensions, crane arrows, drive shafts, tanks and pressure vessels.
• Area of production. Turned seams of welding, soldered seams, cast products, control of endurance of composite materials.
• Checking the materials of aircraft parts, wind turbines, engines.

Application of flaw detectors abroad

In the industry, ultrasonic flaw detectors began to be used in the 1950s. Then the first row of lamp devices was created. Over the past time, extensive experience in the application of the ultrasound method has been accumulated.

In European countries, flaw detection took a firm position. It accounts for one third of the total volume of product inspection. It is also noted that, despite the automation of labor, this method is given the most attention.

This is attributed to the fact that large amounts of work are carried out at such facilities as nuclear power plants, pipelines with different purposes, metal structures, vehicles, etc. A distinctive feature of all the above-mentioned designs is their diversity, which makes the use of automation difficult.

Application of devices in the domestic industry

In the domestic industry ultrasound control occupies a leading position. This is indicated by the number of specialists who are engaged in such work. For example, from 1994 to 2000, according to the Ural Center of Attestation, 1475 defectoscopists were checked. Of these, 38% became professional ultrasound specialists. Distinctive is that the overwhelming number of workers is based on the control of welding seams.

Principle of operation of the apparatus

The work of the ultrasonic flaw detector is based on pulsed radiation. Reflected ultrasonic waves are fixed and make it possible to find defects. Short radio waves are changed by means of piezo-plastics B1-I3. They pass through a layer of contact fluid through the material in the form of a beam with a transverse direction.

The reflected oscillations of ultrasound have an effect on the piezoelectric plates B1 B3. There is an activation of the EMF, which becomes stronger, changes and enters the flaw detector.

Basic methods of control

There are different methods of control. To the most widespread, having high efficiency, it is possible to carry:

• Echo method;
• Method on a mirror-shadow basis;
• Shadow reception.

What does the flaw detector consist of?

What does an ultrasonic flaw detector consist of? The scheme is presented:

• An impulse generator ;
• The defect indicator;
• Broadband amplifying device;
• Device for time equalization of amplitude;
• Stabilizer of supply voltage;
• Converting device.

Scheme of the unit

Electrical circuits of devices such as ultrasonic flaw detectors are quite complex.

The principle of operation of the device can be understood more easily if you carefully read its structure. How to work with a device such as an ultrasonic flaw detector, the instructions will tell you.

The main units of the modern device function according to the following principle:

• A generator that generates sounding pulses generates electrical oscillations that excite ultrasonic waves in the converter device.
• The ultrasonic signals reflected from the defect are received by the same converter (combined circuit or another separate circuit). The signals change into electrical pulses arriving at the input of the amplifier.
• The adjustment of the gain in time is regulated by means of a time control system for sensitivity (SST).
• The signal raised to the desired value is fed to the input of an electric beam indicator and an automatic defect detector (ASD).
• The synchronizing device provides the necessary time sequence for the operation of all nodal areas of the device simultaneously with the start of the pulse generator (or with some specified delay). It facilitates the beginning of the work of the generator of scanning of the electro-beam indicator.
• The sweep makes it possible to distinguish between the arrival time signals of the objects of reflection, which are located at different distances from the converter. The synchronizer is also responsible for controlling the VCR and ASD blocks.
• The devices are stuffed with instruments that measure the amplitude and arrival time of the reflected pulse. The scheme of their inclusion is made in different variations. The measuring device processes signals received from the amplifier taking into account the time of passage of the signal from the synchronizing device, and provides digital indicators on the electro-radiation indicator or a separate scoreboard.

Set up your device

The ultrasonic flaw detector setup begins with the setting of a stable generation in the voltage converter. A resistor R39 is assembled. Then the desired repetition frequency (120-150 imp / s) is obtained, a resistor R2 is assembled.

Amplitude in 70-80 imp / s is achieved by a selection of the diode V1. Then, the capacitors C22 and C26 are selected, which set the limits of variation with the rotating sliders of the resistors R30 and R35 and the pulse duration of the delay monovibrators (10-25 μs) and the controlled zone (7-45 μs).

Verifying the device

Checking the ultrasonic flaw detector is done in various ways:

• The first is the inclusion in the circuit of a special simulation device emitting a test signal. The downside of this device is interference in the device circuit and inability to test the acoustics unit.
• Known and the method conducted by simulating echoes, their radiation in the sample setup. After the reception, the whole electroacoustic path of the flaw detector is checked. There are included the radiating and receiving parts of the electrical unit of the device, which correspond to the PET and electric cables connecting the PES with the unit. The downside of such a check is the use of the method only for flaw detectors with continuous emission of ultrasonic vibrations and for processing signals based on the Doppler effect. Such a decision is unacceptable for the control of most modern models of devices distributed throughout the world.
• Checking the ultrasonic flaw detector is also carried out in a different way. It is based on the fact that the acoustics unit is mounted on the sample setup by applying contact liquid to the sample surface. In this way, an acoustic link is provided between the sample and the acoustics unit. The acoustic unit emits ultrasonic waves into the sample. The echo signals reflected from the internal reflector are received in the sample and amplified. There is a temporary selection, which is fed to the indicators of the device. The quality of the unit is judged by the level of operation of the indicators. To implement this method, metal or organic glass devices with internal reflectors are used. Similar devices are used by all the leading manufacturers of flaw detectors around the world.

Popular models of flaw detectors

From a wide list of devices that are of high quality, we can mention ultrasonic flaw detectors of such manufacturers as OmniScan, Epoch, Sonic, Phasor. And among domestic devices, you should pay attention to the brands UD-2, UD-3, "Peleng", devices series A1212. They are reliable.

Domestic appliances series UD can be attributed to universal, because they not only have a wide range of measurements and technical capabilities, but also can operate in a variety of modes, depending on the conditions and specific purposes. The presence of a wide screen light and sound indicator makes it easier to work with the device.

Foreign manufacturers of ultrasonic flaw detectors produce devices that are characterized by flexible settings. They have a light, durable body, small in size. These are not just flaw detectors, but universal adaptations for the ordinary worker.

For example, the basis of the OmniScan device, which has a rich set of functions, is a phased array. This makes it possible to expand the measurement capabilities and obtain an accurate result.

A wide range of devices should not lead the buyer into confusion. After all, the technical characteristics of ultrasonic flaw detectors are different, and each device has its own advantages and is effective when used under certain conditions.

A universal ultrasonic flaw detector, a device with small dimensions, a device operating at low frequencies, a device equipped with a protective housing - such a rich series makes it possible to find a suitable instrument designed to control elements from a wide variety of materials.

What to look for when buying?

When buying the device, pay attention to the following indicators:

• Portability of the device. Optimal indicator is the light weight of the device. If the device is compact, then it is doubly good.
• Ease of use. The fewer additional settings, the easier it is to work with the unit.
• Reasonable interface. This is very important, because often without special preparation a newcomer can not understand it. The interface really should be understandable, so that there are no problems when you turn on an option.
• Warranty card and service. Be attentive to suppliers and sellers of equipment.
• The device must be suitable for piezoelectric transducers produced abroad. The same is important when buying a domestic device.
• Availability of an understandable, well-laid-out operational instruction.