Sampling rotating drum

Studies of relatively slow segregation in closed sample configurations, such as the rotating drum, are perhaps the easiest granular experiments to perform by MRI. Measurements can be made with the sample stopped the process can continue to evolve between the measurements. As mentioned above, MRI is much easier to perform on stationary systems as opposed to systems undergoing motion. 

A thinner and more uniform slice of the surface can be collected with the Harvey [11] rotating drum sampler. This consists of a floating drum which is rotated by an electric motor, the film adhering to the drum being removed by a windshield wiper blade. The thickness of the layer sampled depends... 

The experiments of Kistiakowsky and Kydd [1] were done by single-pulse photolysis with a 500-J flashlamp, the reaction vessel contents being sampled via a pinhole leak into the electron ionization source of a Bendix time-of-flight (TOF) mass spectrometer. Mass spectra were obtained by pulsed extraction of ions from the ion source at 50-fis intervals after the flash. The signal from the electron multiplier detector was displayed on a cathode ray tube, which was photographed with a rotating drum camera. 

Fig. 10 Rotating drum avalanche data from a TSI Aero-Flow automated powder flowability analyzer. The first frame shows the data output for lactose, which passed through a 38-pm screen (less than 38-pm). The output data for the original lactose sample (notscreened) is shown in the middle frame. The last frame shows the flow data for the lactose sample remaining on the 38- j,m screen (greater than 38-pm). (From Ref l)...

Chase machine Friction sample ( - 25.4 mm square pad) rubbing against the inner diameter of a rotating drum Used to conduct SAE J661 tests for friction edge code determination... 

Daumas et al. (1976) have compared the operation of the rotating drum and screen types of samplers in the field. A detailed examination of their results shows clearly that the surface excesses of different substances analysed in microlayers collected with each device on the same water surface are not equal but vary considerably. There are even cases where some species are enriched in one type of microlayer and depleted in another. This is not so difficult to understand the very wide diversity in surface concentrations in the same patch of water at the same time is well-known (e.g., Parker and Zeitlin, 1972). This type of surface heterogeneity should be borne in mind when the results of different studies are compared. It is possible, nevertheless, that some of this variation arises firom a disturbance of the original surface film by one or both of the sampling devices, i.e., they lose some of the film or its components in an unknown and irregular way. 

Particulate carbohydrates and protein in screen and rotating drum microlayer samples and subsurface seawater, after Daumas et al. (1976)... 

Another grinding tool that is often used to grind soHd samples is the ball miU. A ball mill is a ceramic drum within which is placed the sample and many small balls made of hard ceramic. To grind the sample, the drum is then rotated, and a very fine powder is produced. Ball mills are often used on softer solids, as the time it takes for grinding is directly proportional to the hardness of the material. 

To circumvent the various limitations of the basic technique, several continuous zone refining methods have been developed in which feed enters at one point in the sample while the product and waste leave at other points (Figure 4). The effect of countercurrent movement of solid and liquid phases is achieved by the movement of molten zones. In addition to the horizontal continuous refiner, the zone void vertical refiner and zone transport refiner are other modifications of this class. Cross-flow zone refiners and rotating drum multistage crystallizers based on the above principle are mainly used in growing single crystals rather than in purification of materials. 

The National Bureau of Standards (NBS) Abrader is a frequently used abrasion tester. Test samples are pressed under a specified load against a rotating drum covered with abrasive paper. The number of revolutions of the drum required to wear away a specified thickness of the test specimen is recorded and compared to the number of revolutions required to wear away the same thickness of a standard reference material (ASTM D 1630). 

Therefore, in practice the term sea-surface microlayer has been defined as that thin layer of water that adheres to sampling devices, such as wiremesh screens (Fig. 1-3), glass plates. Teflon disks and rotating drums. For a comparison and discussion of the large variety of different surface film samplers with regard to their sampling efficiencies reference is made to Van Vleet and Williams (1980), Huhnerfuss (1981) or Hardy et al. (1988). 

Figure 1.5. In the free-fall tumblii mixer, a powder to be sampled is homogenized in a sample jar which tumbles chaodcally in a rotating drum. After the tumbling, any sample taken at random from the powder is a representative sample. It is convenient to take random samples using a sampling cup mounted to the lid of the jar [43, 44].

In that test, a mixture of stone chippings and water passes over geotextile samples installed in a rotating drum. The standard test is composed of two abrasion phases at 16 rpm at 40,000 revolutions each, changing direction every 5000 revolutions. If the samples are not degraded after the first 40,000 revolutions (visual inspection), new stone chippings are filled in and the second phase is carried out. If the samples have not been destroyed after 80,000 revolutions, samples are taken and their tensile... 

A rotary drum filter is used to filter a slurry. The drum rotates at a rate of 3 min/cycle, and 40% of the drum surface is submerged in the slurry. A constant pressure drop at 3 psi is maintained across the filter. If the drum is 5 ft in diameter and 10 ft long, calculate the total net filtration rate in gpm that is possible for a slurry having properties as determined by the following lab test. A sample of the slurry was pumped at a constant flow rate of 1 gpm through 0.25 ft2 of the filter medium. After 10 min, the pressure difference across the filter had risen to 2.5 psi. The filter medium resistance may be neglected. 

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