Clearance, annular

Labyrinth Seals The labyrinth is one of the simplest of the many sealing devices. It consists of a series of circumferential strips of met extending from the shaft or from the bore of the shaft housing to form a cascade of annular orifices. Labyrinth seal leakage is greater than that of clearance bushings, contact seals, or filmriding se s. 

BROWN et al.i95) have given data on the performance of 1.5 m diameter sulphonators and nitrators of 3.4 m3 capacity as used in the dyestuffs industry. The sulphonators were of cast iron and had a wall thickness of 25.4 mm the annular space in the jacket being also 25.4 mm. The agitator of the sulphonator was of the anchor type with a 127 mm clearance at the walls and was driven at 0.67 Hz. The nitrators were fitted with four-bladed propellers of 0.61 m diameter driven at 2 Hz. For cooling, the film coefficient hb for the inside of the vessel was given by ... 

If the acceptance criteria given in 1.2.4 are not met, the stiffness or damping coefficients, or both, used in the natural frequency calculation shall be adjusted to produce agreement between the calculated and measured results. The coefficients of one type of element, annular clearances with L/D < 0.15, annular clearances L/D >0.15, impeller interaction, and bearings shall be adjusted with the same correction factor. Once agreement is reached, the same correction factors shall be applied to the calculation of the rotor s natural frequencies and damping for the pumped liquid, and the ro-... 

Note Of the coefficients used in rotor lateral analysis, those for damping in annular clearances have the highest uncertainty and are therefore usually the first to be adjusted. The stiffness coefficients of annular clearances typically have low uncertainty and, therefore, should be adjusted only on the basis of supporting data. Adjustments of bearing coefficients require specific justification because the typical values are based on reliable empirical data. 

The equivalent diameter of the annular jacket geometry is the jacket clearance. If the wall thickness is 0.003 m and the thermal conductivity of the metal is 45 J s 1 K-1 m-2, the overall heat transfer coefficient for the circulating water system is U = 700 J s 1 K 1 m-2. 

For single-flighted screws, Am (indicated in Fig. 6.48 by the dotted area) equals the full cross-sectional area of the annular space between the root of one screw n(Df — 11)11 less the area corresponding to the overlap of the flanks of the flights. Thus neglecting flight clearance, we get... 

Two types of cross-head dies are used for wire and cable coating. The first type is an annular flow or tubing die, where a thin-walled tube is extruded and the molten tube drawn onto the conductor by vacuum after it leaves the die. The vacuum is applied through the clearance between the conductor and the guide, which is usually of the order of 0.2 mm. Tubing dies are commonly used for jacketing cables or coating very thin wires with polymer melts that are very viscous. 

In common design practice, the riser area, total slot area, and passage area in the annular space under the cap are approximately equal in order to reduce pressure losses caused by expansion and contraction. Gas bubbles issuing from the slots are seldom projected more than about 1 in. from the cap, and a clearance between caps in the range of 1 to 3 in. is usually sufficient to eliminate large amounts of undesirable bubble coalescence. The caps should be spaced evenly over the entire tray. A clearance between the shell and adjacent... 

Mold design. PTFE resins are molded in molds similar to those utilized for thermosetting resins or metal powders. A complete mold consists of a cylindrical or rectangular die and upper and lower end plates and a mandrel for annular parts. These parts are normally made of tool steel to allow machining, and plated with chromium or nickel to protect them from corrosion. Occasionally, the end plates are made of brass or plastics such as nylon. A small diametrical clearance is designed in the end plates to allow easy assembly and air escape. 

The main difference in this mixing section is that the outlet channel is open at the start of the mixing section. Thus, not all material is forced over the barrier clearance. Therefore, this mixing device will not result in a uniform shear history of the material. An extreme form of a fluted mixing section is the annular blister ring see Fig. 8.69. 

The annular blister ring is simply a smooth cylindrical screw section with a small radial clearance. All the material has to pass through this clearance to exit from the extruder. Since no positive drag transport takes place over the barrier clearance, the... 

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