NDT(non destructive testing) is used in a variety of settings that covers a wide range of industrial activity.
Ground Penetrating Radar Applications
A home improvement project has to be thought of clearly to be successful without any confusion. Consider what part of the work you think you can do by yourself, without the help of the constructor, like perhaps the painting of the newly added room. You can also lower home improvement costs by considering less expensive alternatives when additions are being designed. For example, choose between a prefabricated fireplace unit and a traditional masonry. Plan all the work that you can do, before giving the contract to the constructor as additional changes made after the contract only leads to additional charges. It is always better to schedule your home improvement schedule to be completed in an off time period of the year. Like it is cheaper installing central air conditioning in winter and not in summer!
If you intend to take on the home improvement project on your own, you have to make sure you have the essential tools for the respective jobs. It is also necessary to be experienced in using the tools, lest you end up with injuries if the equipment is not used correctly. You may find a few home improvement tips on the Internet; but these tips are only feasible for minor repairs. However, it is very important that you have the skills to do the home improvement job. You should undertake any intricate work or a job that needs a high degree of craftsmanship only if you possess the necessary competence. However, it is always better to hire a professional as they will supervise the job from start to finish, and do it at a much better time than you would have taken to do it on your own!
The first thing that has to be done to get a good contractor is, to look around for a good contractor! Good contractors have a fine reputation, and do not mind entering into a contract. It is always better to have an idea of what home improvement you want to be done, before looking for a contractor. Then get recommendations for contractors through friends, neighbors and co-workers. It is always better to approach not one, but 3 to 4 contractors to get estimates of the job to be done. On meeting them, get written estimates for the same work from all of them, to make comparisons. If you want, you can also get references from them, to be contacted. You can then approach the references to find out how the contractors work is.
Once you are satisfied with the contractor, you have to get a written and complete contract. Include the contractors name, address, the total cost of the job, the start and completion date and a description of the project, including the materials to be used, the changes in the order and a written statement giving you the right to cancel the contract within three business days. Add a broom clause in the contract that makes the contractor responsible for all cleanup work of the job, including spills and stains. If you feel that there is something wrong with the contract, it is better to contact an attorney before signing.
Once the contractor is chosen, you have to choose your finance options. If you have cash, then it is fine. Otherwise, you will have to get a home improvement loan that are available in many banks. Consider the interest rates and the benefits of various banks before actually settling down to a choice for your home improvement project. Once the loan is sanctioned, it is always better to avoid paying cash to the contractor. Instead, pay by check and try to limit the down payment. Then make payments during the length of the project contingent on the completion of a definite amount of work. Always keep the final payment and the signing of the affidavit till you are satisfied with the work done, and that you are sure that all the subcontractors and suppliers have been paid.
Instead of getting the contractor to buy all the material, you can supply the materials. In this way, you can shop for materials that are on sale. You are likeable to find building supply stores having various items like tile or wood flooring on sale at one time or the other, due to overstocks or any other factor. If you have the time you could also consider doing the light demolition, painting, garbage removal and landscaping work of the home improvement project. By doing so, you save the money you would have had to pay for labor. Keep all these home improvement tips in mind as it is greatly going to help you in your next major home improvement project!
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X-rays are made by using external radiation to produce images of the body, its organs, and other internal structures for diagnostic purposes. X-rays pass through body structures onto specially-treated plates (similar to camera film) or digital media and a "negative" type picture is made (the more solid a structure is, the whiter it appears on the film).
When the body undergoes x-rays, different parts of the body allow varying amounts of the x-ray beams to pass through. The soft tissues in the body (such as blood, skin, fat, and muscle) allow most of the x-ray to pass through and appear dark gray on the film or digital media. A bone or a tumor, which is more dense than the soft tissues, allows few of the x-rays to pass through and appears white on the x-ray. At a break in a bone, the x-ray beam passes through the broken area and appears as a dark line in the white bone.
X-ray technology is used in other types of diagnostic procedures, such as arteriograms, computed tomography (CT) scans, and fluoroscopy.
When medical X-rays are being produced, a thin metallic sheet is placed between the emitter and the target, effectively filtering out the lower energy (soft) X-rays. This is often placed close to the window of the X-ray tube. The resultant X-ray is said to be hard. Soft X-rays overlap the range of extreme ultraviolet. The frequency of hard X-rays is higher than that of soft X-rays, and the wavelength is shorter.
Hard X-rays overlap the range of "long"-wavelength (lower energy) gamma rays, however the distinction between the two terms depends on the source of the radiation, not its wavelength; X-ray photons are generated by energetic electron processes, gamma rays by transitions within atomic nuclei.
Since antigen's discovery that X-rays can identify bony structures, X-rays have been developed for their use in medical imaging. Radiology is a specialized field of medicine. Radiographers employ radiography and other techniques for diagnostic imaging. Indeed, this is probably the most common use of X-ray technology.
X-rays are especially useful in the detection of pathology of the skeletal system, but are also useful for detecting some disease processes in soft tissue. Some notable examples are the very common chest X-ray, which can be used to identify lung diseases such as pneumonia, lung cancer or pulmonary edema, and the abdominal X-ray, which can detect ileus (blockage of the intestine), free air (from visceral perforations) and free fluid (in ascites).
In some cases, the use of X-rays is debatable, such as gallstones (which are rarely radiopaque) or kidney stones (which are often visible, but not always). Also, traditional plain X-rays pose very little use in the imaging of soft tissues such as the brain or muscle. Imaging alternatives for soft tissues are computed axial tomography (CAT or CT scanning), magnetic resonance imaging (MRI) or ultrasound. Since 2005, X-rays are listed as a carcinogen by the U.S. government.
Diagnostic x-rays are safe. But who hasnt wondered about them when undergoing a chest x-ray, mammogram, routine dental x-rays, or an x-ray for a broken bone?
The safety of routine X-rays has been called into question following the unexpected discovery that cells exposed to low doses avoid or delay repairing damaged DNA.
Puzzlingly, cells given higher doses of X-rays were faster and more efficient at patching up any damage. But the German researchers who made the discovery say it is not clear whether the sloppy repairs that follow low level exposure is a good or bad thing.
Kai Rothkamm and Markus Brich, at the University of Saarland in Homburg, acknowledge that unrepaired breaks in DNA could well lead to cells becoming cancerous. But it is equally possible, they say, that the failure to repair low-level DNA damage has evolved as a safety measure.
Other experts state that no scientific data indicate any danger. In fact, there is evidence that low doses may actually reduce the chance of cancer. The question about the amount of radiation you receive is difficult for x-ray technicians and doctors to answer because very few x-ray units have an instrument to measure the radiation to the patient.
You may have heard that even the smallest amount of radiation may cause cancer. Based on this unscientific assumption, the risk of causing a fatal cancer from a chest x-ray is 10 times greater than the risk of dying in a commercial airline flight. Or a CT scan of the kidneys has a greater risk of inducing a fatal cancer than a cigarette smoker has of dying from any cancer. These statements produce unnecessary worry. There is no data to show any risk from diagnostic x-rays.
Lastly, radiation during pregnancy may lead to birth defects. Always tell your radiologist or physician if you suspect you may be pregnant.
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Salt spray testing under ASTM B117 conditions subjects the test samples to conditions that are actually more corrosive than usual “real world” exposure. This is because the test uses sodium chloride in de-ionized water and usually lacks the moderating effects of other dissolved salts such as those containing calcium and magnesium, which tend to be somewhat protective.
is the most popular form of testing for protective coatings. These tests have been used for more than 90 years as accelerated tests in order to determine the degree of protection afforded by both inorganic and organic coatings on a metallic substrate. The most widely used salt spray (fog) tests are described below.
The neutral salt spray (fog) test (ASTM B 117): is perhaps the most commonly used salt spray test in existence for testing inorganic and organic coatings, in particular where such tests are used for material or product specifications. The duration of the test can range from 8 to over 3000 hours, depending on the product. A 5% sodium chloride solution containing not more than 200 parts per million (ppm) total solids and with a pH range of 6.5 to 7.2 is used. The temperature of the salt spray chamber is controlled to maintain 35 + 1.1 or – 1.7Þ C (95 + 2 or -3Þ F) within the exposure zone of the closed chamber.
The acetic acid salt spray (fog) test (ASTM G 85, Annex A1): is also used for testing inorganic and organic coatings, but is particularly applicable to the study or testing of decorative chromium plating and cadmium plating on steel or zinc die castings, as well as for the evaluation of product quality. This test can be as short as 16 hours, although it normally ranges from 144 to 250 hours or more. Similar to the neutral salt spray test, a 5% sodium chloride solution is used, but the solution is adjusted to a pH range of 3.1 to 3.3 by the addition of acetic acid. The temperature of the salt spray chamber is controlled to the same temperature range as for neutral salt spray.
The copper accelerated acetic acid salt spray (fog), or CASS test (ASTM B 368): is primarily used for the rapid testing of chromium plating on steel and zinc die castings. It is also useful in the testing of anodized, chromated, or phosphated aluminum. The duration of this test ranges from 6 to 720 hours. A 5% sodium chloride solution is used, with one gram of copper (II) chloride dihydrate added to each 3.8 liters of salt solution. The solution is then adjusted to a pH range of 3.1 to 3.3 by adding acetic acid. The temperature of the salt spray chamber is controlled to the same temperature range as for neutral salt spray and for acetic acid salt spray.
Ultrasonic Testing (UT) uses high frequency sound energy to conduct examinations and make measurements. Ultrasonic inspection can be used for flaw detection/evaluation, dimensional measurements, material characterization, and more. To illustrate the general inspection principle, a typical pulse/echo inspection configuration as illustrated below will be used.
A typical UT inspection system consists of several functional units, such as the pulser/receiver, transducer, and display devices. A pulser/receiver is an electronic device that can produce high voltage electrical pulses. Driven by the pulser, the transducer generates high frequency ultrasonic energy. The sound energy is introduced and propagates through the materials in the form of waves. When there is a discontinuity (such as a crack) in the wave path, part of the energy will be reflected back from the flaw surface. The reflected wave signal is transformed into an electrical signal by the transducer and is displayed on a screen. In the applet below, the reflected signal strength is displayed versus the time from signal generation to when a echo was received. Signal travel time can be directly related to the distance that the signal traveled. From the signal, information about the reflector location, size, orientation and other features can sometimes be gained.
Ultrasonic Inspection is a very useful and versatile NDT method. Some of the advantages of ultrasonic inspection that are often cited include:
As with all NDT methods, ultrasonic inspection also has its limitations, which include:
The above introduction provides a simplified introduction to the NDT method of ultrasonic testing. However, to effectively perform an inspection using ultrasonics, much more about the method needs to be known. The following pages present information on the science involved in ultrasonic inspection, the equipment that is commonly used, some of the measurement techniques used, as well as other information.
Leak testing equipment is used to measure the escape of liquids, vacuum or gases from sealed components or systems. Some configurations require a separate leak detector or sensor as an input. Such types of leak testing equipment are often equipped with various other components such as pumps, calibrators, gauges and cases. Output options include analog voltage, analog current, frequency or modulated frequency, and switch or alarm signal. Some leak testing equipment includes an analog front panel with potentiometers, dials, and switches. Other features a digital front panel that is set up with a keypad or menus. Leak testing equipment with a serial interface, a parallel interface, and/or integral application software is also available.
Leak test method is an important specification to consider when choosing leak testing equipment. Methods include bubble testing, colorimetric development, electronic gas detection, mass flow, mass spectrometry, and hydrogen leak detection. Bubble testing is used for applications which do not require high sensitivity. A pressurized test object is submerged in a water tank so that the emergence of bubbles indicates a leak. Colorimetric development uses a chemical developer which reacts with the leaking fluid, causing a visible color change to occur at the place of leakage. Leak testing equipment that uses electronic gas detection pressurizes the test object with a tracer gas so that a sniffer probe can be used to find the leak. Mass flow devices direct the leakage across a heating element. The temperature change produces an output voltage proportional to mass flow. Mass spectrometers are used with helium leak detection. Leak testing equipment that is designed to detect hydrogen leaks is also available.
