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NACE MR0175 and the evaluation and acceptance criteria for the Four Point Bend (FPB) test

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QUESTION:
This inquiry for help with interpretation concerns the clause NACE MR0175/ ISO 15156-2 B.4.2.3 Evaluation and acceptance criteria for FPB test specimens.
1) It is written “Damage developed on the tensile side of a specimen in the form of blisters less than 1 mm below the surface, or on the compression side regardless of the depth of the blister, may be disregarded for the assessment of SOHIC/SZC but shall be reported”
Question : Does this means that Damage developed on the tensile side of a specimen in the form of blisters MORE than 1 mm below the surface has to be considered as not allowed/not acceptable or should only be reported as “blisters more than 1 mm below the surface”? (See below) Example 1: No blisters deeper than 1mm in the tension side are allowed (?)
2) It is written “No ladder-like HIC features nor cracks exceeding a length of 0.5 mm in the through thickness direction are allowed”
Question: Are cracks developed inside an area affected by a blister disregarded for the assessment (cf. example 2 picture)? In other words: Shall the damage in example 2 be reported as:
A) a blister?
B) a crack?
C) a blister and a crack?
ANSWER:
Question 1: “Damage developed on the tensile side of a specimen in the form of blisters less than 1 mm below the surface, or on the compression side regardless of the depth of the blister, may be disregarded for the assessment of SOHIC/SZC but shall be reported”. Does this means that Damage developed on the tensile side of a specimen in the form of blisters MORE than 1 mm below the surface has to be considered as not allowed/not acceptable or should only be reported as “blisters more than 1 mm below the surface”?
Answer 1: Blisters greater than 1 mm below the surface are not acceptable.
Question 2: “no ladder-like HIC features or cracks exceeding a length of 0.5 mm in the through thickness direction is allowed”. Are cracks developed inside an area affected by a blister disregarded for the assessment (cf. example 2 picture)? In other words: Shall the damage in example 2 be reported as:
A) a blister?
B) a crack?
C) a blister and a crack?
Answer 2: if both cracks and blisters are present as defined Clause B.4.2.3, they both need to be reported.
This question is in relation to NACE MR0175/ISO 15156-2 B.4.2.3
Reference: ISO 15156 Maintenance Panel Inquiry #2016-12

UPDATE: A new standard for Four Point Bend has been published by NACE. NACE TM0316 2016 addresses four point bend testing for sour service. Read a review of the document following this link:

NACE TM0316, a new standard for Four Point Bend testing for Oil & Gas applications

Contact us to discuss Four Point Bend testing requirements.

 

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