Norwegian Oil and Gas Association, Recommended Guidelines for NDT of GRP pipe systems and

tanks

No.: 055 Date effective: 01.03.97 Revision no: Date revised: Page: 16

(Table 2.1, cont.'d:)

DEFECT TYPE DESCRIPTION SUITABLE NDT TECHNIQUES ANNEX

SPOOL / JOINT DEFECTS:

GRP MATERIALS

DEFECTS:

Delaminations Area where plies within GRP

laminate become separated

Visual inspection

Ultrasonics

Thermography

Radiography

Acoustic emission

A

B

C

D

F

Fractures and cracks Cracking through the GRP wall

thickness, fiber breakage

Visual inspection (e.g. dye

penetrants)

Acoustic emission

(propagating cracks)

Ultrasonics

Radiography

A

E

C

D

Matrix cracking Cracking in resin-rich layers,

without fiber breakage

Visual inspection(e.g. dye

penetrants/felt-tip pen)

Acoustic emission

(propagating cracks)

A

E

Microcracking (crazing) Fine hairline cracks at or under

the surface of the laminate.

Visual inspection A

Incorrect volume fraction

of fibers

Insufficient strength from too few

fibers; dry spots where the

reinforcement has not been

wetted by resin.

Radiography

Pressure testing

Microscopic examination (of

cross-section)

E

B

Improper fiber

alignment/poor

distribution

Microradiography E

Incorrect cure of matrix Barcol hardness

DSC

Acoustic emission

G

H

F

Porosity, voids, and

inclusions in matrix

Air, outgassing during cure,

foreign matter cured into the

laminate

Radiography

Ultrasonics

Acoustic emission

E

C

F

Erosion

Internal, localised material

removal by abrasive erosion or

cavitation

Visual inspection (internal)

Ultrasonics

Thermography

Radiography

A

C

D

E