Magnetic Particle Testing

Wide range of dredge ball joints introduced by Dredge Yard

In order to provide customer with the best suitable solution and lowest cost, Dredge Yard specialists designed the dredge ball joints in 6 different types, giving variations of tilting angle from 15 to 18 degrees and duties for operating from 10 bar to 30 bar. All the details about the sizes can be found on Dredge Yard site www.dredgeyard.com. The materials used for the production depends on each part of the dredge ball joints. Because the case and the ball need a high elongation and impact value, cast iron of a manganese alloy is used. The material needs for the gland are cast iron of a chromium, nickel and molybdenum alloy that provides a high tensile strength, high yield point and high hardness values. For wear resistant properties of the liner, ductile manganese iron or hard chromium iron is used. The production of dredge ball joints is done at a high quality and experienced foundry with the latest production facilities to ensure high quality casting and quick delivery time. To ensure that all parts are identical and interchangeable, the patterns are made from aluminum or hard wood. All castings of dredge ball joint are heat treated according to ISO and ASTM standards and they are measured and tested before machining. After machining and before releasing for the transport, all the products are measured and tested again. During and after production all products undergo a systematically testing including chemical composition and mechanical properties test, measurement test of all dimensions after casting, ultra sonic test, magnetic particle test, surface roughness test and dye penetrant inspection for critical parts, measurement test of all dimensions after machining, hardness test, assembly and interchange ability test, and visual inspection for all parts. This wide range of dredge ball joints bring a lot of benefits such as easy assembly or dis-assembly, low required maintenance, quick fix and release of locking.

Magnetize to Find Discontinuities with Magnetic Particle Inspection

Magnetic particle inspection successfully detects surface and near surface defects in ferromagnetic materials such as steel and iron. This is just one of a few types of nondestructive testing "http://www.labtesting.com/services-nondestructive-testing.php" or NDT inspection methods often performed at testing laboratories such as Laboratory Testing Inc. Any of the nondestructive testing methods allow materials and products to be tested or inspected without damage. Some other nondestructive testing processes include liquid penetrant inspection, ultrasonic testing, radiographic or X-ray inspection, visual inspection and hydrostatic pressure testing. Magnetic particle inspection "http://www.labtesting.com/services-magnetic-particle.php" is performed by spreading fine magnetic particles over the surface of a test piece as it is being magnetized, causing a buildup of particles at a discontinuity such as a crack, lap, inclusion or seam. These particles have high magnetic permeability, so they are easily magnetized and attracted to small magnetic leakage fields caused by discontinuities. A trained and experienced nondestructive testing technician will interpret the indications that might be observed during the inspection. Dry particles are most commonly used for convenience in field inspections. Fluorescent wet inspection is considered best for detecting very small discontinuities because much smaller particles are used and the liquid carrier allows the particles to flow easily to small leakage fields to form indications. A wet magnetic particle inspection has an advantage over a dry inspection because the equipment used in this process can quickly and easily spray a uniform layer of particles over the surface of the material or part to be inspected. The magnetic field can be produced by the use of direct current (DC) circuits or by alternating current (AC) circuits. AC circuits produce fields that are confined to the near surface of the test sample and are useful in finding surface cracks. DC circuits provide magnetic fields that penetrate a shallow distance into the test sample and are useful for also finding discontinuities below the surface. At Laboratory Testing, the most common method used for magnetic particle inspection is the fluorescent wet continuous method using full wave direct current (FWDC). The part is placed into one of our three wet fluorescent horizontal units and then the magnetic field is applied while the suspension of magnetic particles is sprayed or poured over the test sample. The horizontal magnetic particle inspection units range in size from 6 ft. to 12 ft. long. Larger size parts are inspected using cables, yokes and portable equipment. There is relatively no limit to the size of parts that can be inspected using the magnetic particle inspection method, except for limitations due to the capacity of the test equipment. High currents are usually needed to inspect large parts. Inspections need to be performed in two directions to insure detection of discontinuities in the longitudinal and circumferential directions. No extensive or elaborate pre-cleaning of parts is required before inspection; usually only solvent degreasing is needed to remove oils. Paint, heat-treat scale, grease, etc. should be removed to provide the most accurate test results. Magnetic particle inspections can be performed before and after plating. It is standard practice to demagnetize parts following inspection and post-clean the parts to remove magnetic particles. A variety of standards and specifications are used as the basis for performing magnetic particle inspection. These include sections of American Society of Materials Engineers (ASME) Codes, Aerospace Material Specifications (AMS), Society of Automotive Engineers (SAE) Specifications, American Society for Testing and Materials (ASTM) Standards, various military standards, and the American Society for Nondestructive Testing (ASNT) Recommendations.

Magnetic Particle Testing Equipment

Magnetic Particle Testing Welding

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