Laboratory Testing is a full-service material testing provider with complete in-house resources to turn your order around quickly and reliably. LTI performs destructive and non-destructive weld testing to verify that a welding procedure and welds produced according to the procedure meet requirements. Welding coupons and specimens are also prepared onsite in our machine shop.

The results of all qualification testing are documented in certified reports.

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Welding Procedure Qualification The welding procedure is reviewed in detail, then testing and inspection is performed on welds produced in accordance with the procedure to verify all requirements are met. Weld coupon testing often includes visual examination, mechanical testing, metallographic examination and nondestructive testing. LTI may also assist with preparation of Welding Procedure Qualification as per client or project requirements. Welder Qualification After confirmation that a welding procedure meets a specified standard, welders may be qualified for the procedure.

The welder qualification test is generally required to support welder certification. Contact LTI to discuss your requirements for welding procedure qualification or welder qualification services. Examination for characteristics such as weld size, fusion, penetration, profile, and weld discontinuities is performed at magnifications anywhere between 1X and 50X. The weld test for hardness evaluates the strength of the weld and is performed on a ground and etched sample, similar to the macroetch specimen. This generally involves checking the hardness in all three zones, including weld , HAZ and base according to a pattern prescribed by the referenced specification.

Hardness testing of welds is an extremely common practice and requirement in the oil and gas industry.

When a large number of coupon tests are performed on the same material then the amount of scatter in the mechanical properties is quantified. For example, Fig. The mean property value is , although the measured properties vary from about 72 to Example of the number and types of coupon and element tests used to evaluate a new composite material for an aircraft structure. Representation of statistical variations in the mechanical properties of materials.

Large databases which quantify the amount of scatter in the mechanical properties are essential for safe aerospace design. The databases are used to determine the so-called material allowables that are used in design analysis. The material allowables are often given under the headings of A or B.

The A basis allowable defines the mechanical property values for materials used in safety critical aircraft structures such as the fuselage, wings and undercarriage. The confidence required in the property values for these materials is critical to aircraft safety. The B basis allowable is less stringent, and is applied to components where material failure does not result in the loss or excessive damage to the aircraft. James G. Surface monitors include test coupons placed at strategic points in the Flowline and also more sophisticated techniques that attempt to measure corrosion rates directly resistance devices, polarization devices, galvanic probes, hydrogen probes and iron counts.

In the past, the onset of well problems instigated monitoring.

While waiting for a failure is not recommended, recovering corroded tubing or casing at least provides valuable after-the-fact information, and every opportunity is taken to find out what caused the corrosion and the failure Figure 8. Some downhole monitoring techniques have been adapted to logging pipelines.

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The same surface logging equipment is used, but the logging tools themselves have been made more flexible to pass around sharp bends. Short lengths of pipe may be logged by this method but longer lengths are usually monitored by smart pigs. These are sophisticated instrument packages, which use ultrasonic, flux leakage, and other electromagnetic techniques to check for corrosion.

The data are usually stored in the pig itself for later retrieval. The pig is pumped along a pipeline from a launching station to a purpose-built receiving section of the pipeline. Surveys cover tens or even hundreds of miles.

In corrosion coupon tests, metal coupons of known metallurgy, size, shape and weight are exposed to a corrosive environment with and without the addition of corrosion inhibitors, and are inspected for corrosion after a period of time e. Corroded coupons are subjected to visual and optical or microscopic examination, weight loss measurement, and surface analysis by various surface analytical techniques.

Weight-loss coupons are widely used in REM inhibitor research under variously selected environmental conditions.

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Davo et al. The metallurgical phases responsible for the corrosion and inhibition process were identified with a scanning electron microscope SEM coupled to an energy dispersion spectroscopy system EDS , before and after 1-hour, hour and 1-month immersion in a 3.

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The compounds formed on the alloy surface were analyzed by X-ray photoelectron spectroscopy XPS. Shi et al. The test solutions were produced by dissolving supersaturated cerium cinnamate into 0. The inhibitor film was also observed by an atomic force microscope AFM. XPS was used for the identification of different elements present on corrosion coupon surfaces.

Markley et al. Coupons were polished, cleaned, air dried and immersed in solutions of 0. Blin et al. Ethanol was added to solutions to help the dissolution of the inhibitor, and was evaporated from the solution prior to testing by heating the solution above the boiling temperature of ethanol for several hours. The pH of the test solutions was between 5. Weight loss measurements were performed as a starting point to estimate relative corrosion rates in control and inhibited systems.

ATR-FTIR vibrational spectroscopy was used to examine the nature of the inhibiting complexes attached to the metal surface without the removal of the film. Corrosion coupons are an excellent source of corrosion information if monitoring is carried out correctly and maintained continuously. However, coupon tests have well-known limitations: they are considered to be time consuming and labor intensive.

They may require periodic removal of the test specimen from the corrosive environment, which is cumbersome and may alter the progress of localized corrosion. They only detect the cumulative corrosion damage at the end of the exposure period and provide little information on specific events that may have triggered this damage.

Although the corrosion coupon test appears to be an easy task, there are in fact problems that often lead to unsuccessful and misleading results. An example is the testing for underdeposit corrosion. If a corrosion coupon is fully covered by sand, it would not simulate important galvanic corrosion effects and thus underdeposit corrosion problems would not be detected. The electrical resistance probe monitors corrosion by measuring the electrical resistance of a thin metal wire which increases as the wire becomes thinner because of corrosion dissolution.

An advantage of the probe is that it provides a measure of cumulative metal loss without the need to remove it from the service environment. A major disadvantage of the electrical resistance technique is that it is unable to detect localized corrosion as localized corrosion may neither lead to significant metal dissolution, nor noticeable change in electric resistance. It generally does not respond rapidly to a change in corrosive conditions. For this reason, the electrical resistance probe is not a preferred technique for accelerated laboratory corrosion inhibitor tests.

For the same reason, physics-based corrosion inspection methods such as ultrasonic and radiographical testing are used mainly for field inspection of corrosion damages and cracks; they are rarely used in accelerated laboratory corrosion and inhibitor tests. Ashcroft, P.

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Briskham, in Advances in Structural Adhesive Bonding , Mechanical testing can range from inexpensive coupon tests through testing of structural elements to testing of full prototypes, which may be extremely expensive. In all cases, fatigue testing will be considerably lengthier and more costly than quasi-static testing.

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The coupon tests can fulfil a number of roles. Single material tests may be used to generate material property data whilst joint tests can be used to compare material systems or joint geometries, evaluate performance over a range of loading and environmental conditions, generate design data or provide validation data for predictive models. Typical joint samples are similar to those used in quasi-static testing. Fatigue testing of these joints will generally be carried out with uniaxial, constant amplitude, sinusoidal waveforms. In most cases the waveform will have a positive maximum, such that the sample remains in tension throughout, avoiding buckling of the sample.

As these tests are relatively inexpensive they are often used to explore the effects of contributing factors to the fatigue life of bonded joints, such as test environment, preconditioning, frequency and R -ratio the ratio of minimum to maximum fatigue load. This information can then be used to select the most damaging cases for use in structural element or prototype testing. The structural element tests are designed to represent accurately a particular joint or joints in a structure. Samples will be more complex than the simple coupon tests and loading may now be multiaxial.

The increased cost of these tests means that fewer will be carried out. The final testing is of a prototype in which the bonded joints will only be one part of what is being tested. Testing will be under simulations of severe in-service use. Failure at this point can have significant financial repercussions. The former recommends that at least four samples should be tested at three different stress amplitude values for a given stress mean, such that failure occurs between 10 4 and 10 6 cycles.

This standard also provides advice about statistical analysis of the data. In general, fatigue data exhibit greater scatter than quasi-static data and this needs to be taken into account when using safety factors with fatigue data.

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Further advice on the application of statistics to fatigue data is found in Bs Steven E. A welder is qualified by welding a test coupon in accordance with an approved welding procedure. The main purpose of this qualification test is to prove that the welder has the knowledge, skill and dexterity necessary to produce a weld that meets the requirements of the relevant standard or specification. Welder qualification testing is generally the responsibility of the manufacturer or contractor but some standards require the test to be witnessed by an independent third party examiner.

One of the duties of a welding inspector is to oversee a welder qualification test being carried out and ensure that it is being done in compliance with the requirements of the relevant code or specification. A common question asked is whether a welder who welds a test coupon to qualify a new welding procedure is automatically qualified to weld that procedure even though the coupon has in effect been welded using an unqualified procedure.

If not, it means that the welder would have to weld to the procedure once it was qualified to gain the qualification. The answer is very simple; it depends on what the standard says. European standards will normally permit this but others may not. It is important to be aware of the differences between standards in how welders are qualified.

Many fabricators require their welders to be qualified to both if they are required to comply with the requirements of ASME and the requirements of European directives such as the Pressure Equipment Directive PED. The ideal situation would be to qualify welders to both standards on the same form using the same test coupon, but unfortunately this is not possible because the qualified thickness ranges, pipe diameters and the non-destructive testing and destructive testing requirements are different.