Table 5-4. Couplant Materials for Contact Inspection.
Approximate Surface Roughness
(microinches, m in)
SAE 10W motor oil
SAE 20-20W motor oil
SAE 30W motor oil
SAE 40W motor oil
Guidelines for Inspector Familiarization.
Familiarization with the methods and equipment can be obtained by:
a. Performing the familiarization tests included in the instrument manuals.
b. Performing the calibration procedures given in Section 5.2.
c. Making distance amplitude correction curves and establishing transfer on some specimens as described
in paragraph 22.214.171.124.1..
d. For surface wave familiarization, perform the tests given in paragraph 126.96.36.199.3.
All these familiarization tests and procedures should be followed in detail by the new operator. It is recommended that
the procedures be run through several times. The operator should experiment with various combinations of specimens
and search units to become familiar with different ultrasonic inspection procedures and equipment.
Contact and Immersion.
Ultrasonic inspections can be separated into two basic categories: contact inspection and immersion inspection
(paragraph 5.1.3). Immersion inspections are no longer confined to a tank of water in a laboratory or factory.
Bubblers, squirters, or water columns enables the use of immersion techniques with portable ultrasonic scanning
equipment in field inspections.
Common Inspection Methods.
Straight Beam Method.
This method uses longitudinal waves (paragraph 188.8.131.52).