Test method wall thickness

With this testing method an evaluation is possible within shortest time, i.e. directly after the heat impulse. The high temperature difference between a delamination and sound material is affected - among other parameters - by the thickness of the layer. Other parameters are size and stage of the delamination Generally, a high surface temperature refers to a small wall thickness and/or layer separation [4],... 

The accuracy of the presented methods was verified using test pipes with various diameters and wall thickness of which the wall thickness was measured independently using a slide-rule. Both on film and on the monitor the wall thickness could be determined within an accuracy of ca. 0.2 - 0.3 mm. 

Figure I represents a two-dimensional damage distribution of an impact in a 0/90° CFRP laminate of 3 mm thickness. Unlike in ultrasonic testing, which is usually the standard method for this problem, there is no shadowing effect on the successive layers by delamination echos. With the method of X-ray refraction the exact concentration of debonded fibers can be calculated for each position averaged over the wall thickness. Additionally the refraction allows the selection of the fiber orientation. The presented X-ray refraction topograph detects selectively debonded fibers of the 90° direction.

For pipelines in service in chemical plants, it is not usually convenient to place a radiation source inside the pipe and position it to irradiate each welded joint. The radioisotope source container maybe placed on the outer surface of the pipe. The radiation beams then pass through two pipe wall thicknesses to expose films placed diametrically opposite the radiation source, also on the outside of the pipe wall. Other methods, such as magnetic particle inspection of welds in steel pipe, or ultrasonic inspection of welds in pipes of all materials, supplement x-rays in many critical appHcations. The ultrasonic tests can often detect the thin, laminar discontinuities parallel to the pipe surface or the incomplete fusion discontinuities along the weld... 

As decribed in Chapter 4.3.2, it is increasingly common to design and manufacture such apparatus as monobloc reactors. Furthermore with modem testing facilities with, for example, ultrasonic methods it is possible to check the finished apparatus up to wall-thicknesses of 350 mm. These developments are an excellent contribution for the safe operation of high-pressure vessels. 

C) Disc Method of Hercules Powder Company. In this test procedure, the expl is loaded into steel pipe bombs 1 or 2 in diam and of varying wall thickness from 1/8 to 1/4". Instead of the usual screw cap, a base plate can be welded to the bomb, or omitted, and the assembly can be backed... 

The wall thickness of the prosthesis is measured using a fabric thickness tester as per the ASTM Standard Test Method D1777 under a small but known appHed pressure. In order to remove the crimps the prosthesis is flattened by mounting between two glass sHdes and the thickness, h, is calculated by subtracting the thickness of the slides. 

The first method was employed with both neptunium and plutonium when these metals were tested for superconductivity down to temperatures of about 0.75°K [1]. Brass capsules of 1 mm wall thickness were used which had at one end platinum—glass seals through which the platinum wires for the current-potential measurement were passed. The active specimens were inserted into the capsules inside a glove box in which the electrical contacts were also made and in which the capsule was filled with helium gas and then sealed off. Prior to its introduction into the glove box, the capsule had been covered with a layer of shellac. After sealing off, the capsule was immersed in acetone which dissolved the shellac and in this manner the contamination sticking to the outside of the capsule was removed. 

Measured on an axially symmetrical test bottle with an average wall thickness of 0.7-1 mm, by method of R. Holzmann, Kautex-Werke, Hangelar. 

The statistical analysis procedure most useful in evaluating corrosion on pipes is the extreme value statistical method. The referenced publications provide details on extreme value statistics and their application to pipeline corrosion. The extreme value statistical approach analyzes the maximum pit depth (or minimum wall thickness) per unit length to estimate the range of corrosion data for the pipe. The results, of course, assume that the pipe run is in the same condition as the sample tested. The more samples tested, the greater the accuracy of the result. 

The decision to test is usually driven by unusual chemistry such as a new catalyst, reaction components, or reaction conditions. Immersion/mass loss method is primarily used in conjunction with microscopic examination. Process fluids from production or pilot runs are primarily used to best simulate potential corrosion. The test methods are custom designed based, in part, on cost and the ability to obtain sufficient quantities of test fluids, and handle the process conditions. Process conditions are tested outside the process control limits (e.g., temperatures, pH) to better accentuate the corrosion potential. These extremes have to be tempered by the stability of the products in the stream. For wall thicknesses greater than 0.250 in. (6.35 mm), a uniform loss of less than 10 mil/year (0.26 mm/year) is considered structurally acceptable. Signiflcandy lower levels of uniform loss are of concern for product or process contamination issues. Microscopic examination is used to determine potential localized corrosion concerns, such as pitting or stress cracking. Indications of pitting or stress corrosion in stamped areas of the coupon are of particular concern. U-bend tests are rarely used because of insufflcient test fluid quantities and availability. 

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