Standard Practice for Phased Array Ultrasonic Testing of Polyethylene Electrofusion Joints

Importancia y uso:

5.1 This practice is intended for the semi-automated or automated ultrasonic examination of electrofusion joints used in the construction and maintenance of polyethylene piping systems.

5.2 Polyethylene piping has been used instead of steel alloys in the petrochemical, power, water, gas distribution, and mining industries due to its reliability and resistance to corrosion and erosion.

5.3 The joining process can be subject to a variety of flaws including, but not limited to: lack of fusion, cold fusion, particulate contamination, inclusions, short stab depth, and voids.

5.4 Polyethylene material can have a range of acoustic characteristics that make electrofusion joint examination difficult. Polyethylene materials are highly attenuative, which often limits the use of higher ultrasonic frequencies. It also exhibits a natural high frequency filtering effect. An example of the range of acoustic characteristics is provided in Table 1.6 The table notes the wide range of acoustic velocities reported in the literature. This makes it essential that the reference blocks are made from pipe grade polyethylene with the same density cell class as the electrofusion fitting examined.

(A) A range of velocity and attenuation values have been noted in the literature (1-9).

5.5 Polyethylene is reported to have a shear velocity of 987 m/s. However, due to extremely high attenuation in shear mode (on the order of 5 dB/mm (127 dB/in.) at 2 MHz) no practical examinations can be carried out using shear mode (6).

5.6 Due to the wide range of applications, joint acceptance criteria for polyethylene pipe are usually project-specific.

5.7 A cross-sectional view of a typical joint between polyethylene pipe and an electrofusion coupling is illustrated in Fig. 1.

FIG. 1 Typical Cross-Sectional View of an Electrofusion Coupling Joint

Subcomité:

E07.06

Referida por:

E0543-21, E0543-21

Volúmen:

03.04

Número ICS:

23.040.60 (Flanges, couplings and joints)

Palabras clave:

electrofusion; phased array; polyethylene; ultrasonic;