Application of Couplant in Ultrasonic Testing
Ultrasonic couplant is a kind of crucial material in contacting ultrasonic measurement. It is used for remove the air between the probe and the workpiece, making it easy to penetrate the tested workpiece and achieve the target of measurement. If poor coupling results in an air layer between the probe and the inspected workpiece, it can interfere with the effective transmission of ultrasound and make routine inspection impossible.
Why Do We Need High-Temp Couplant
High-temperature workpiece should be selected with high-temperature coupling agent is because the room temperature coupling agent in contact with high-temperature objects, will be instantly evaporated or dried off, resulting in ultrasonic waves difficult to reach the measured workpiece.
Especially in the case of high-temperature detection, detection time is very short, high-temperature probe can only be in the high-temperature measurement of the surface of the workpiece for a short time (generally 5-10 seconds), otherwise it will reduce the service life of the probe or even damage the probe. Therefore, such harsh conditions must have a high-temperature coupling agent can be resistant to high temperatures to ensure that the probe and the workpiece between the good coupling and protection of the probe, to achieve the desired purpose of detection. The coupling agent should be used in the right amount, coated evenly, the coupling agent should be coated on the probe.
How To Choose Correct Couplant
High temperature couplers are specially designed for ultrasonic testing in higher temperature environments and have good thermal insulation properties. It is suitable for ultrasonic testing of workpieces at higher temperatures (e.g. above 60℃ or even higher).
But as a continuous measurement at high temperatures with the coupler, in addition to the above should have the main performance of the ordinary coupler, should also meet the following requirements:
a.with a wide range of operating temperature range, viscosity with the temperature change is small,the couplant is not easy to be evaporated under high-temperature environment.
b.weak volatility, which means that it is conducive to long-term work at high temperatures.
c.the composition is stable, high temperature long-term work physical and chemical properties do not change.
We selected several high-temperature coupling agents from several domestic and foreign manufacturers for comparative testing. The tests address several aspects of high temperature coupling agents, including temperature resistance, sound transmission, odor and cleaning treatment.
1#, domestic, nominal temperature up to 550°C
2#, Ushi Pioneer, nominal temperature up to 540 ° C
3#, imported, the nominal temperature up to 600 ° C
4#, imported, the nominal temperature up to 675 ℃
The Result Of Comparision
The above test situation shows that 2# YUSHI HUC-2 high-temperature coupling agent performs well in terms of temperature resistance, sound transmission, as well as odor and cleaning treatment.
★ Sound transmission effect is better, coupling loss is small, in favor of ultrasonic measurement.
★YUSHI high-temperature coupling agent among several liquid coupling agents has the best temperature resistance, it has good fluidity, does not solidify and dry up, and is able to maintain measurement.
★After heating, the odor is mild and not pungent, and the residue is easy to clean and dispose of.
This high-temperature coupling agent HUC-2 capacity 50ml/bottle, temperature range 25 ~ 540 ℃, ferrous metal rustproof grade of 90, biodegradable, non-toxic, harmless, irritating odor is small.
The above test shows that when measuring at high temperature, 1# and 3# are more resistant to temperature, but the sound transmission is not good, high degree of curing leads to not good coupling, not suitable for high temperature measurement. 4# at a temperature of 300 ℃ sound transmission is better, can be used for high temperature measurement. When the temperature reaches 450 ℃, in the selection of high-temperature coupling agent need to pay special attention to the ignition point, that is, the spontaneous combustion temperature. Never use a couplant at temperatures higher than the auto-ignition temperature. For critical or delicate components, couplants from trusted manufacturers that meet NDT requirements are recommended.