Firstly,  the professional QC do the tests and inspection as per customers’ requirement or standards

Items:

Visual Inspections
a. Inspect and take measurements of the thickness of the pipes and ensure the numbers conforms to design specifications.
b. Inspect for indentations, pitting, cracks, uneven surfaces

Mechanical Inspection
a. Perform the impact resistance test to determine the impact strength
b. Test the tensile strength of the pipes to determine how the material reacts to forces being applied in tension.
c. Perform the deflection temperature test to ensure the pipe sample deforms under a specified temperature and conforms to international standards

Packaging Inspections
a. Check packaging materials by comparing them with approved samples and specifications.
b. Inspect necessary packaging marks including model number, quantity per packaging, name, place of distributor's business, country of origin, logos and marks from standards organizations, stacking, and handling marks.
c. Check the safety markings for clarity, size, color, conspicuousness, etc.

Secondly, the third party from the SGS, Bv, DNV, LR, etc. Appointed by customers

Required Documents for Third Party Inspector Review;
Third-Party Inspection for Line Pipe - Material Inspection;
Third-Party Inspection for Line Pipe - Manufacture;
Third-Party Inspection for Line Pipe Inspection during Manufacturing;
Third-Party Inspection for Line Pipe Hydrostatic Testing;
Third-Party Inspection for Line Pipe Visual and Dimensional Examination;
Third-Party Inspection for Line Pipe Marking;
Third-Party Inspection for Line Pipe - Reporting;
Third-Party Inspection for Line Pipe - Release Note;
Third-Party Inspection for Line Pipe Packing, Marking, and Shipping;
Third-Party Inspection for Line Pipe Documentation.

Thirdly, End-user(Clients) confirm the final quality 

1. Related report check and review, such as mill test certificate, 3rd party inspection report;

2. Visual review: welding, surface, straightness, package, marking;

3. Tool test: sizes(out diameter, wall thickness, length) with relative tools, hardness;

4. Machine retest: hydrostatic, pressure;

5. Professional experienced persons in charge check.