Quality

Quality testing

A.D. TUBI INOSSIDABILI S.P.A.’s strong point is the quality of the products we supply to our customers. From the very first days of our company we’ve always paid utmost attention to our quality system and quality department and with two in-house laboratories, fully equipped both for destructive and non-destructive testing we are in the position to immediately assess the quality of our production and to investigate any condition of material.
Following the most stringent requirements of standards ruling production of our welded tubes we pride ourselves to manufacture high quality products for the most demanding markets.

Duly certified as per ISO 9001- ISO 14001 - BS OHSAS 18001 plus AD2000 W0-W2, PED, NACE, GOST R, Lloyd’s, Rina, DNV, Norsok we can grant complete suitability of our products to our customers’ needs.

All manufactured tubes are technologically tested according to QCP linked to every production. All tests are performed IN HOUSE thus having immediate results allowing us to assess the quality of our products.

Destructive tests

Flattening test

EN ISO 8492 / ASTM A370

Used to test the transverse weld ductility on the outside surface. A specimen is flattened in a press to evaluate distance between the platens. Standard distance between the platens for A.D. Tubi is 20% greater than what prescribed by standards. Cracked samples are rejected. Testing frequency is according to production standard; however, one test is performed at least every two hours.

Drift Expanding test

EN ISO 8493

This test is used to determine the ability of metallic tubes of circular cross-section to undergo plastic deformation in drift expansion. We expand the end of the specimen by a conical mandrel until the maximum outside diameter of the expanded tube reaches the value specified in the relevant product standard. A.D. Tubi standard expansion is always greater than 20% for duplex steels and nickel alloys and greater than 25% for austenitic steels. Upon customer request, for special alloys, expansion can be greater than even 40-50%. Cracked samples are rejected. Testing frequency is according to production standard; however one test is performed at least every two hours. 

Reverse Flattening test

ASTM A370

Used to test the transverse weld ductility on the ID surface, thus determining properties required in the product specification. The specimen consists of a length of tubing approximately 100mm long which is slit longitudinally 90° on each side of the weld. The sample is then opened and flattened with the weld at the point of maximum bend.  Cracked samples are rejected. Testing frequency is according to production standard; however one test is performed at least every two hours.

Flange test

ASTM A370

Used to test longitudinal weld ductility of the tubes and their ability to withstand the operation of bending into a tube sheet. A section of tube shall be capable of having a flange turned over at a right angle to the body of the tube to the width required by the applicable material specification without cracking or showing imperfections. Testing frequency is according to production standard; however, one test is performed at least every two hours. 

Flaring Test

ASTM A370

This test consists of driving a tapered mandrel having a slope of 60° into a section cut from the tube and thus expanding the specimen until the inside diameter has been increased to the extent required by the applicable material specifications. As per drift expanding test the A.D. Tubi standard is greater than ASTM standard. Cracked samples are rejected. Testing frequency is according to production standard, however one test is performed at least every two hours. 

Reverse Weld Bend test

EN ISO 5173 / ASTM A370

Test is done to assess the welding strength of the tubes. Cracked samples are rejected. Testing frequency is according to production standard; however, one test is performed at least every two hours. 


Mechanical testing

Hardness test

ASTM E92 / UNI EN ISO 6507

Hardness, while technically not a material property, is used to quickly determine if the material is suitable for its intended use. Hardness test (HV10) is performed on each lot produced. One test is performed on each production beginning. Frequency of test is defined by related production standard.

Microhardness test

EN ISO 6507 / ASTM E384

From 0,3HV to 10HV both on base metal, HAZ and Welded Metal.

Microhardness test is performed upon customer request. A.D. Tubi can perform microhardness test from 0,3HV to 10HV on base metal, heat affected zone and welded metal. To see typical micro-hardness test values, see material technical sheet for further information.

Tensile Test

ASTM E8 / EN ISO 6892-1

A sample of tube is subjected to a controlled longitudinal tension force until it breaks, allowing us to measure ultimate tensile strength, breaking strength and maximum elongation. A tensile test is performed on each lot produced. Frequency of test is defined by related production standard. A.D. Tubi records values of Rp0,2, Rp1, Rm and elongation% for each test carried out.

Hot Tension Test

EN ISO 6892-2 / ASTM E21

By this method we test the material properties at an elevated temperature.

Burst test

Burst test is a test that can be carried out upon customer request to determine the burst pressure of tube. It is a test useful to find the admissible stress (σAD), which, starting from burst pressure, can be find with the Barlow’s equation.

P = 2St /D

P = pressure
S = allowable stress
t = wall thickness
D = outside diameter

Other Tests

  • Residual Circumferential stresses test
    ASTM E1928 Thirkell test
    This test estimates the approximate residual circumferential stress in our tubes from the change in outside diameter that occurs upon splitting a length of the tube. A specimen with a length of approximately 100mm is longitudinally split and then diameter is measured at 90° from splitting. A.D. Tubi tubes have a very low residual stress.
  • Residual longitudinal stresses test
    Tongue Test
    The tongue test is performed if the order requirements foresee an evaluation of the residual stresses embedded longitudinally in the material due to mechanical work performed during the production of the tube itself. Three sides of a rectangle are cut from the tube and the opening of this “tongue” is measured and related to longitudinal stresses.
  • Welded seam measurement
    Height of the weld seam can be measured using a special gage. Internal height of the weld seam from inside bead rolled tubes, for common tubes, is typically under 0,05mm. External weld seam, when grinded, is close to zero.

Non destructive testing

Operators qualified acc to ISO 9712 and SNT-TC-1A (III level and II level)

Dimensional Control Test

Our operators perform diameter, wall thickness and length control according to a frequency set in production standard. All measurement gauges are certified and periodically calibrated. Upon customers’ request also internal diameter can be measured using specific gauges.

Eddy Current Testing

EN ISO 10893-1 / EN ISO 10893-2 / ASTM E426 / ASTM E309 / ASTM E571

Eddy current testing is performed in-line on 100% of tubes produced according to EN 10893-1/10893-2 or ASTM E426-E573-E309. Eddy current calibration and verification is performed by A.D. Tubi level II and III qualified staff according to EN473 and EN- ISO9712. Non conform tubes are automatically segregated in non-conform area.

Ultrasonic Test (UT)

EN ISO 10893-10 / EN ISO 10893-11 / ASTM E213

UT can be performed on 100% of produced tubes. Test is carried out in-line on finished tubes before cutting and after eddy current. Calibration and verification is performed by A.D. Tubi level II qualified personnel according to EN ISO 9712.

Air Under Water Test (AUW)

ASTM A1016

A.D. Tubi can perform AUW on its tubes according to EN1779 and/or ASTM/ASME A/SA 1016. AUW can be performed on 100% of tubes upon customer request. Each tube with an internal surface clean and dry, shall be internally pressurized to 150 psi (1000 kPa) minimum with clean and dry compressed air while being submerged in clear water. After holding the pressure for not less than 5 seconds after the surface of the water has become calm, the entire external surface of the tube is inspected. Any tube showing leakage is rejected.

Differential Air Pressure Test

ASTM A1047 / EN1779

DPT is carried out according to ASTM A1047/1047M-05 Pr.A and EN1779.
A.D. TUBI performs leak testing using DPT because of its higher sensibility and its objective result compared with HT and AUW.

Other Tests

  • Visual Examination Test
    EN ISO 17367
    Visual Examination is constantly performed by our operators. Operators examine the welded seam, surface condition, internal and external cleanliness of the tubes.
  • Hydrostatic Test (HT)
    ASTM A450 / EN 10217-7
    Hydrostatic Testing is the a most commonly used method of leak testing to determine and verify the integrity of the tube. A.D. Tubi can perform HT on 100% of tubes upon customer request up to pressure of 250bar.
  • Dye Penetrant Test (PT)
    EN ISO 10893-4 / ASTM E165
    Liquid penetrant testing methods indicate the presence, location and to a limited extent, the nature and magnitude of the detected discontinuities. It is based on the ability of a liquid to be drawn into a “clean” surface discontinuity by capillary action. The penetrant liquid is applied on the tube surface (suitably cleaned). Then it’s necessary to wait for a suitable time so that the liquid owing to capillary action goes inside the discontinuities. Then the excess of liquid is removed from the surface. At this step a developer is applied to the tube covering the whole surface.
    Finally, the penetrant containing a contrasting colour, which persists inside the discontinuities can be observed.

Corrosion tests

Various corrosion tests can be performed in our laboratories in order to evaluate tubes corrosion resistance to intergranular, pitting and crevice corrosion or to detect the presence of intermetallic phases.

  • EN ISO 3651-1 (Huey Test)
  • EN ISO 3651-2 Pr.A - Pr.B - Pr.C

EN standard to determine the resistance to intergranular corrosion of stainless steels, ferritic, austenitic and duplex materials.

  • ASTM A262 Pr.A - Pr.B - Pr.C - Pr.E - Pr.F
  • ASTM A763 Pr.X – Pr.Y – Pr.Z
  • ASTM A923 Pr.A, Pr.B and Pr.C

These standards specify Intergranular Test used to detect sensitization from slow cooling rates, insufficient annealing, or carbon and nitrogen contamination.

  • ASTM G28 Pr.A and Pr.B
  • ASTM G48 Pr.A - Pr.B - Pr.C - Pr.D - Pr.E - Pr.F

These tests are acid based pitting and crevice corrosion tests that are intended to mimic potential applications.
ASTM G28 (also known as green death) is the standard test method for detecting susceptibility to intergranular corrosion in nickel-rich, chromium-bearing alloys.

ASTM G48 is the standard method for pitting and crevice corrosion resistance of stainless steels and related alloys by use of ferric chloride solution.

Other Tests

  • Weld decay test
    A249 S7
    Weld decay test is the standard method for evaluating welding corrosion rate in stainless steels.

Other non destructive testing

Austenite/ferrite balance

ASTM E562 / ASTM E1245

Austenite/Ferrite balance test is carried out to verify the percentage of austenite phase and ferrite phase in duplex steels. Test is performed according to ASTM E562 (systematic manual point count) or ASTM E1245 (automatic image analysis). In A.D. Tubi's laboratory it is possible to check the correct balance of the two phases, both in base metal, heat affected zone and welded metal. A.D. Tubi's standard percentage of austenite in welded metal is between 40% and 60%, depending on the raw material percentage. 

Roughness measurement

EN ISO 4287

Roughness measurement is performed upon customer request to evaluate the roughness of tubes produced. Test is carried out with calibrated profilometer. Roughness values depend strictly on raw material surface condition, so special tubes roughness values must be agreed on.
A.D. Tubi personnel can measure following surface parameter:

  • Average roughness (Ra, AA, CLA)
  • Root-mean square roughness (Rq, RMS)
  • Maximum peak to valley height (Ry, Rmax)
  • Ten point height (Rz)

Grain Size Determination

ASTM E112

Grain size determination is a test carried out to check the micro-structural grain dimension. Test is carried out according to ASTM E112. Grain dimension depends on grade and heat treatment performed. The focus of the test is determining the grain size number G corresponding to a certain average grain area. Typical A.D. Tubi tubes grain size of welded metal and heat affected zone is very close to metal base grain size.

Positive Material Identification (PMI)

Positive material identification is a test to verify the material grade. It is not a chemical analysis. A.D. Tubi perform PMI for every incoming strip to verify the grade. Upon customer request this test can be performed even on finished tubes.

Macrographic analysis

ASTM E381

This analysis is carried out to evaluate the shape and penetration of the weld which is evidenced by cutting a sample from the tube, polishing and etching one of its transversal sides.

Micrographic analysis

ISO 17639 / ASTM E3 / ASTM E407

Micrographic analysis is carried out to check the quality of the weld or to verify other characteristic's such as absence of intermetallic phases. A portion of tube is embedded in resin and then polished. After polishing, the sample is etched with an adequate etchant (different for every grade and scope) and then observed under the optical microscope. Microstructure, presence of micro-porosity and intermetallic phases can be verified.

SEM Analysis and EDS analysis

A.D. Tubi can perform special analysis using its scanning electron microscope. SEM analysis is very useful to check some particular aspects out, like segregations of second phases, micro-porosity, presence of unwelcomed elements. For example, it is very useful to control the presence of molybdenum segregations in 6%Mo alloys. (However, the application field of SEM is so wide that it cannot be summarized here.)

Ultrasonic wall thickness measurement

Wall thickness can even be measured using a ultrasonic device for special applications.

Product Analysis

ASTM E1999

Standard test method for Analysis of material by Optical Emission Spectrometry giving us the chemical composition of the product.

Other Tests

  • Chloride salt test determination
    A/SA 688
    Chloride salt determination test is carried out to detect eventual chloride residuals on finished tubes. Test is performed according to ASTM/ASME A/SA 688. The content of Cl-ions is evaluated in deionized water in contact with a sample of finished tube. Typical values are less than 1ppm of Cl- ions.