True Devices

Flow is an important measurement whose calibration presents some challenges. When a flow measurement device is used in applications such as custody transfer, provision is made to pass a known flow through the meter. However, such a provision is costly and is not available for most in-process flowmeters. Without such a provision, a true cahbration of the flow element itself is not possible. For orifice meters, calibration of the flowmeter normally involves cahbration of the differential pressure transmitter, and the orifice plate is usually only inspected for deformation, abrasion, and so on. Similarly, cahbration of a magnetic flowmeter normally involves cahbration of the voltage measurement circuitry, which is analogous to calibration of the differential pressure transmitter for an orifice meter. 

The stirring produces the end product in the desired divided-sohds form. Hence, it is frequently termed a granulator or a ciystaUizer. A variety of factoiy-made sizes in various materials of construction are available. Initial cost is modest, while operating cost is rather high (as is true of all batch devices), but the ability to process gummy burdens and/or simultaneously effect two unit operations often yields an economical application. 

Practical separation techniques for hquid particles in gases are discussed. Since gas-borne particulates include both hquid and sohd particles, many devices used for dry-dust collection (discussed in Sec. 17 under Gas-Sohds Separation ) can be adapted to liquid-particle separation. Also, the basic subject of particle mechanics is covered in Sec. 6. Separation of liquid particulates is frequently desirable in chemical processes such as in countercurrent-stage contacting because hquid entrainment with the gas partially reduces true countercurrency. Separation before entering another process step may be needed to prevent corrosion, to prevent yield loss, or to prevent equipment damage or malfunc tion. Separation before the atmospheric release of gases may be necessaiy to prevent environmental problems and for regula-toiy compliance. 

A relationship of power consumption to collection efficiency is charac teristic of all particulate scrubbers. Attaining increased efficiency requires increased power consumption, and the power consumption required to attain a given efficiency increases as the particle size of the dust decreases. Experience generally indicates that the power consumption required to provide a specific efficiency on a given dust does not vary widely even with markedly different devices. The extent to which this generahzation holds true has not been fully explored, but the known extent is sufficient to suggest that the underlying collection mechanism may be essentially the same in all types of particulate scrubbers. 

Location of Vacuum Relief Device (Carl Schiappa, Michigan Engineering, The Dow Chemical Company, Midland, Mich., personal communication, March 20, 1992.) If a vacuum relief device is used, locate the device at the highest point on the top of the tank. If the vacuum relief device is not installed in this location and the tank is overfilled with liquid, the relief device will be sealed in liquid and will be ineffec tive in protecting the tank. This is especially true for the part of the tank above the vacuum relief device if it is sealed in liquid, tne liquid level is lowered, and the tank goes into a partial vacuum. 

The ability of a measuring system (device, person, and environment) to measure true values to the accuracy and precision required. 

Volume 1 explains that pumps ean be classified as either positive-displacement or kinetie. The same is true for compressors. In a positive displacement compressor the gas is transported from low pressure to high pressure in a device that reduces its volume and thus inereases its pressure. The most common type of positive displacement eompressors are reeiprocating and rotary (serew or vane) just as was the ease for pumps. Kinetic compressors impart a veloeity head to the gas, which is then converted to a pressure head in accordance with Bernoulli s Law as the gas is slowed down to the velocity in the discharge line. Just as was the case with pumps, centrifugal compressors are the only form of kinetic compressor commonly used. 

Electrical supply systems and equipment are grounded in order to maintain the voltage at any part of the system at a known potential relative to true earth and to provide a path for current flow under earth fault conditions so that protective devices operate correctly. The connection to earth should be such that the flow of fault current to earth does not cause voltages or voltage gradients to be of sufficient magnitude or duration likely to cause danger. 

Displacement, or eddy-current, probes are designed to measure the actual movement, or displacement, of a machine s shaft relative to the probe. Data are normally recorded as peak-to-peak in mils, or thousandths of an inch. This value represents the maximum deflection or displacement from the true centerline of a machine s shaft. Such a device must be rigidly mounted to a stationary stmcture to obtain accurate, repeatable data. See Figure 43.21 for an illustration of a displacement probe and signal conditioning system. 

A reactive polymer (RP) is simply a device to alloy different materials by changing their molecular structure inside a compounding machine. True reactive alloying induces an interaction between different phases of an incompatible mixture and assures the stability of the mixture s morphology. The concept is not new. This technology is now capable of producing thousands of new compounds to meet specific design requirements. 

When symmetry is given, there is no need to consider the flow in a micro device or even a micro channel as a whole, but favorably one can refer to only a small part of it and regard this as a true functional region. A first-approach description for slug flow, according to the above consideration, may therefore refer to the repeti-... 

External numbering-up benefits from true repetition of the fluidic path, and hence preserves all the transport properties and hydrodynamics, determined in advance for a single-device operation. This is commonly believed to result in a... 

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