Page 90 - Chemical Process Equipment - Selection and Design

62 DRIVERS FOR MOVING EQUIPMENT
TABLE 4.1. Selection of Motors for Process Equipment TABLE 4.2. Checklist for Selection of Motors

Motor Typea Motor Data
Application A.C. D.C. General
Type of motor (cage, wound-rotor, synchronous, or dc). .......
Agitator la,lb,2b 5a
Ball mill IC, 2b, 3a 5b Quantity. ....... Hp ........ Rpm ......... Phase .........
Blower la, 1 b, 2b, 3a, 4 5a Cycles. ....... Voltage.. ......
Compressor la, 1 b, IC, 3a, 4 5b, 7 Time rating (continuous, short-time, intermittent) ............
Conveyor la,lc,2b,3a 5b. 7 Overload (if any) ..... .% for ...... Service factor ...... %
Crusher la, IC, Id 5a, 5b Ambient temperature. ........ .C Temperature rise. ........ .C
Dough mixer la,lb,lc,2b 5a, 5b Class of insulation: Armature. .. Field. .. Rotor of w-r motor.. .
Fan, centrifugal and propeller la, 1 b, 2c. 3a. 4 5a. 7 Horizontal or vertical. ........... Plugging duty.. ..........
Hammer mill IC 5a Full- or reduced-voltage or part-winding starting (ac) ........
Hoist 1 d, 2a. 3b 6 If reduced voltage-by autotransformer or reactor, .........
Pulverizer IC 5b Locked-rotor starting current limitations.. ...................
Pump, centrifugal la, 1 b, 2b, 3a, 4 5b Special characteristics.. ...................................
Pump, positive displacement IC, 2b, 3a 5b
Rock crusher 3a 5b, 6 Induction Motors
a Code: Locked-rotor torque.. ....... % Breakdown torque.. ...... .%
1. Squirrel-cage, constant speed or for general-purpose cage motor: NEMA Design (A, B, C, D)
a. normal torque, normal starting current ..............................
b. normal torque, low starting current
c. high torque, low starting current Synchronous Motors
d. high torque, high slip
2. Squirrel-cage, multispeed Power factor.. .... Torques: Locked-rotor.. ... % Pull&.. ... %
Pull-out.. .... % Excitation. .... .volts dc Type of exciter. .....
a. constant horsepower
b. constant torque If m-g exciter set, what are motor characteristics?. ...........
c. variable torque Motor field rheostat.. ...... Motor field discharge mistar.. .....
3. Wound rotor
a. general purpose Direct-current Motors
b. crane and hoist Shunt, stabilized shunt, compound, or series wound. ............
4. Synchronous Speed range. ......... Non-reversing or reversing. ............
5. Direct current, constant speed Continuous or tapered-rated. ...............................
a. shunt wound
b. compound wound
6. Direct current, variable speed series wound Mechanical Fcatuns
7. Direct current, adjustable speed Protection or enclosure.. ............ Stator shift.. ...........
(After Allis-Chalmers Mfg. Co., Motor and Generator Reference
Book, Colorado Springs, CO). Mechanical Features (ant.)
Standard NEMA ratings for induction motors: Number of bearings.. ........... Type of bearings.. ..........
General purpose: ;, :, 1. I:, 2,3, 5,7$, IO, 15, 20, 25, 30, 40, 50, 60, Shaft extension: Flanged.. ..... Standard or special length.. ....
75, 100, 125, 150, 200, 250, 300, 350, 400,450, 500. Press on half-coupling.. ...... Terminal box.. ................
Large motors: 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000, NEMA C or D flange.. ...... Round-frame or with feet.. ......
1250, 1500, 1750,2000, 2250, 2500,3000,3500,4000,4500,5000 and up Vertical: External thrust load. ... .lbs. Type of thrust bearing.. ...
to 30,000. Base ring type.. .............. Sole plates.. ...............
Accessories ...............................................
Clearly the cost increments beyond the basic drip-proof motor
Load Data
enclosures are severe, and may need to be balanced in large sizes Typeofload ..............................................
against the cost of isolating the equipment in pressurized buildings If compressor drive, give NEMA application number.. ...........
away from the hazardous locations. Direct-connected, geared, chain, V-belt, or flat-belt drive. .........
Wk' (inertia) for high inertia drives. ................... lb-ft'
Applications. The kinds of motors that are being used Starting with full load, or unloaded.. .........................
successfully with particular kinds of chemical process equipment are If unloaded, by what means?. .............................
identified in Table 4.1. As many as five kinds of AC motors are For variable-speed or multi-speed drives, is load variable torque,
shown in some instances. The choice may be influenced by constant torque, or constant horsepower?. .....................
economic considerations or local experience or personal preference. Operatingconditio ........................................
In this area, the process engineer is well advised to enlist help from
electrical experts. A checklist of basic data that a supplier of a (By permission, Allis Chalmers Motor and Generator Reference
motor must know is in Table 4.2. The kind of enclosure may be Book, Bul. 51R7933, and E.S. Lincoln (Ed.), Electrical Reference Book,
specified on the last line, operating conditions. Electrical Modernization Bureau, Colorado Springs, CO.

4.2. STEAM TURBINES AND GAS EXPANDERS
4. simple controls,
Turbines utilize the expansion of steam or a gas to deliver power to 5. low first cost and maintenance, and
a rotating shaft. Salient features of such equipment are 6. flexibility with regard to inlet and outlet pressures.

1. high speed rotation, Single stage units are most commonly used as drivers, but above
2. adjustable speed operation, 500W or so multistage units become preferable. Inlet steam
3. nonsparking and consequently nonhazardous operation, pressures may be any value up to the critical and with several