Typical retest steel material

An upgrade or retest material are normally retest mechanical properties, chemical composition and supplementary testing as agreement between the fabricator and supplier.

The reason of the testing may be based on the unknown material (lost markings),an unlisted approval vendor list, or re-verification of material, etc.

These material shall be subjected to test under supervision of quality department and Client’ representative inspector.

re-test material steel

Which methods are normally request to retest?

  • Destructive Test: Tension test, chemical analysis, guided bend test/flattening test, proof test, hardness test (mock up/internal survey) , CVN test, etc.

  • Non-Destructive Test: Visual/dimensional inspection, wall thickness, RT/UT for weld same, MT/PT on all surface, eddy current test alternative for hydrotest, PMI, etc.

Which material are normally subjected to re-test?

Pipe, plate, or larger fitting are considered the test. Which fittings are long enough to prepare the test specimens like tension test.

How to test on small pipe fitting ASME B16.9?

The testing are based on the agreement between Fabricator and their Client. Mechanical test may be alternated the test by proof test and this purpose to reconfirm after forming without leakage/ withstand the design pressure.

In order to small fitting may be subjected to proof test by caped the end of fitting. The test coupon shall be tested after welding, PWHT.

The test medium may be portable water or rust inhibitor.

Re-Test for Pipe and Plate

Representative pipe segment shall at last 200 mm in length or enough length for the test. If small ID pipe (NPS1" and under) shall be tested with full length.

Method of testing may be re-verified the MTC or as agreed between fabricator and their Client. Sampling of piece shall be selected each heat number or product number, lot number/batch number or project specifications.

  • Mechanical properties: tension test (longitudinal / transverse), bending/flattening test,

  • Chemical composition: chemical analysis,

Supplementary requirements: wall thickness verification, visual/dimensional inspection, nondestructive test, hardness survey, etching tests, grain size determinations (stainless steel), intergranular corrosion test (stainless steel), etc.

Re-Test for flanges and flanged fittings

No recommendation for testing because of higher fees of re-test are compared with order new one, I recommend to purchase a new product.

If flanges and flanged fittings are required to the test, the test sample shall be destroy from product to enough size to jaw on the machine, in case of length of sample was less then the requirement, it may be extent the sample by welded. Sampling of piece shall be selected each heat number or product number, lot number/batch number or project specifications.

  • Mechanical properties: tension test,

  • Chemical composition: chemical analysis,

Supplementary requirements: visual/dimensional inspection, nondestructive test, hardness survey, etching tests, grain size determinations (stainless steel), intergranular corrosion test (stainless steel), etc.

Re-Test for pipe fittings

Pipe fitting had wrought from pipe accordance to ASME B16.9 as above metions.

The larger sample may be destroy to size and conduct the test as above example retest for pipe and plate.

The smaller samples or larger sample may be subjected to proof test.

The mechanical test and composition analysis refer to the example of retest for pipe/plate. Below is example burst test:

Design proof test

The test shall be taken to rupture or held at or above the computed minimum proof pressure for a period of at least 3 min. The test is successful if for each of the tests, the fitting withstands without rupture a proof test pressure at least equal to the computed minimum.

Test pressure P = 2.S.t.f / D

where:

  • D = specified outside diameter of pipe,
  • f = testing factor (refer to ASME B16.9 para. 9.3)
  • P = computed minimum proof test pressure for fitting,
  • S = actual tensile strength of the test fitting, determined on a specimen representative of the test fitting, which shall meet the tensile strength requirements of the applicable material (MTC must be available for reviewing),
  • t = nominal pipe wall thickness of the pipe that the fitting marking identifies

Sampling of test: as agreement between Fabricator and their Client by lot/batch number; or product number; range, thickness or grade; or at least three specimen tests for each fitting, joint size, or configuration are recommended as below:

  • No of test = 1 ; test factor f = 1.1;
  • No of test = 2 ; test factor f = 1.05;
  • No of test = 3 ; test factor f = 1.00;

Note: liquid-filled pressure gauges for protection against vibration, pulsation and suddenly drooping pressure.

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