Speeds critical

At a given gas sparging rate, interfacial area a is constant at low mixer speeds. When mixer speed is increased above a critical speed a starts increasing and varies linearly with Ai For Rushton turbines this critical speed, as deterrnined in an sodium sulfate system, is given by the following ... 

Critical speed analysis and the influence of bearing stiffness on this analysis... 

Inverters make it possible to control a variable-speed fan by changing the frequency modulation. Standard alternating-current fan motors may be speed-regulated between 0 and 60 Hz. In using inverters for this apphcation, it is important to avoid frequencies that would result in fan critical speeds. 

Similar applications to log washer, but lighter action. Tumbling (85% critical speed) provides attrition to remove clay from sand. Also removes trash. 

N, Critical speed of mill r/min r/min A75 Particle size corresponding to 75 percent cm in... 

The criterion bv which the baU action in mills of various sizes may be compared is the concept of critical speed. It is the theoretical speed at which the centrifugal force on a ball in contacl with the mill shell at the height of its path equals the force on it due to gravity ... 

Speed of mill affects capacity, also liner and ball wear, in direct proportion up to 65-75 percent of critical speed. 

The required disc-rotation speed is given in terms of the critical speed, i.e., the speed at which a single pai-ticle is held stationary on... 

At certain speeds, rotating masses become dynamicatty unstable and cause deflection and vibration in the rotor w hich may damage the motor. The speed at w hich such instability occurs is known as critical speed and occurs at different multiples of the rated speed. The masses must therefore rotate within 20T beknv or above the critical speeds to avoid such a situation. These vibrations settle down again at higher speeds above critical and recur at the next higher critical speed. 

The first or free-free rotor bending mode frequency (based on the required margin for operation below the critical speed)... 

Increasing speed to an rpm at die lower limit of die critical speed range... 

Traversing rapidly dirough die critical speed range Waiting for new steady state at about 90% of nominal speed... 

Expander-compressor shafts are preferably designed to operate below the first lateral critical speed and torsional resonance. A flame-plated band of aluminum alloy or similarly suitable material is generally applied to the shaft in the area sensed by the vibration probes to preclude erroneous electrical runout readings. This technique has been used on hundreds of expanders, steam turbines, and other turbomachines with complete success. Unless integral with the shaft, expander wheels (disks) are often attached to the shaft on a special tapered profile, with dowel-type keys and keyways. The latter design attempts to avoid the stress concentrations occasionally associated with splines and conventional keyways. It also reduces the cost of manufacture. When used, wheels are sometimes secured to the tapered ends of the shaft by a common center stretch rod which is pre-stressed during assembly. This results in a constant preload on each wheel to ensure proper contact between wheels and shaft at the anticipated extremes of temperature and speed. 

Critical speed is when the frequency of a periodic exciting frequency applied to the rotor-bearing support system corresponds to the natural frequency of the system. 

The following describes some of the commonly used squeeze film dampers and introduces one of the more novel damper designs, which clearly has application in turboexpanders. Examples of the optimization process required in the design and selection of squeeze film dampers and their applications to solve stability and critical speed problems are also demonstrated. 

Appears suddenly at or above rotor critical speed when critical is below one-half operating speed. Increasing speed increases vibration amplitude, blit whirl frequency remains constant. When speed IS decreased, vibration disappears below where it first appeared. Fnction-indnced rotor whirl Encountered m bnilt-np rotors or rotors with shrink fits or rotor disassembly to inspect fits, increase shrink fits Coupling friction has been known to induce whirl... 

Vibration peaks at specific speeds peaks can usually Rotor critical speeds CO... 

Appears on gears like rotor critical speed. Vibration Torsional resonance Usually occurs only during startup... 

EiTatic high-frequency vibration amplitude and possibly an audible sound. Rotor mb Labyrinth mbs generally self-comect Disc mbs due to thrust bearing failure often self-comect temporarily through wean steel on steel shrill noise during wear Rotor deflection is critical speed... 

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