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Balance Quality Requirements of Rigid Rotors - …

World's Leading Supplier of Soft Bearing Balancing Machines & Instruments Balance Quality Requirements of Rigid Rotors The Practical Application of ISO 1940/1. IRD Balancing Technical Paper 1. Balance Quality Requirements of Rigid Rotors The Practical Application of ISO 1940/1. ABSTRACT USING THE STANDARD. International Standard ISO 1940/1 is a widely- The use of the standard involves the following accepted reference for selecting Rigid rotor steps: Balance Quality . This paper is presented as a tutorial and user's reference of the standard and 1. Select a Balance Quality grade "G number". its practical applications. from Table 1 based on rotor type. A simplified method is shown for determining 2. Use the Figure 1 (A or B) graph to determine permissible residual unbalance for various rotor the permissible residual specific unbalance classifications.

2 Table 1 Balance quality grades for various groups of representative rigid rotors (From ISO 1940/1) Balance Quality Grade Product of the Relationship

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Transcription of Balance Quality Requirements of Rigid Rotors - …

1 World's Leading Supplier of Soft Bearing Balancing Machines & Instruments Balance Quality Requirements of Rigid Rotors The Practical Application of ISO 1940/1. IRD Balancing Technical Paper 1. Balance Quality Requirements of Rigid Rotors The Practical Application of ISO 1940/1. ABSTRACT USING THE STANDARD. International Standard ISO 1940/1 is a widely- The use of the standard involves the following accepted reference for selecting Rigid rotor steps: Balance Quality . This paper is presented as a tutorial and user's reference of the standard and 1. Select a Balance Quality grade "G number". its practical applications. from Table 1 based on rotor type. A simplified method is shown for determining 2. Use the Figure 1 (A or B) graph to determine permissible residual unbalance for various rotor the permissible residual specific unbalance classifications.

2 Emphasis is given to allocating value, eper for the rotor's maximum operating permissible residual unbalance to appropriate speed and the selected "G number." Then correction planes for rotor configurations, such multiply eper by rotor weight to obtain the as unsymmetrical, narrow and overhung Rotors . permissible residual unbalance, Uper. Finally, a comparison of various Balance Quality grades is made with MIL-STD-167-1 and API 3. Allocate Uper to the balancing correction Balance limits. planes based on rotor configuration. INTRODUCTION Performing step 1 simply requires the user to The International Standards Organization, ISO, find the rotor type that most nearly describes published Standard 1940/1 " Balance Quality the one to be balanced. Requirements of Rigid Rotors ," which has been adopted by the American National Standards Step 2 is more involved as it requires using the Institute, ANSI, as , " Balance Quality graph in Figure 1 to find the permissible specific Requirements of Rotating Rigid Bodies.

3 " It has unbalance, followed by multiplying by rotor also been adopted by BRITISH Standards as BS weight and then a constant to convert Uper to 6861: Part 1 and by GERMAN Standards as VDI proper units (gram-millimeters or ounce-inches). 2060. This step can be simplified by using some simple equations to calculate Uper directly. ISO 1940/1 requires an understanding of balancing and its terminology if the standard is Step 3, allocating Uper, is often not performed to be understood and used properly. The because it is not easily understood. reader is directed to the paper's " Balance Terminology" section for a summary of terms Therefore, the following pages provide a used in this paper. simplified method for step 2 and describe the procedures for step 3. 1. Table 1 Balance Quality grades for various groups of representative Rigid Rotors (From ISO 1940/1).

4 Balance Product of the Quality Relationship Rotor Types - General Examples Grade (eper x v) (1) (2). mm/s G 4 000 4 000 Crankshaft/drives(3) of rigidly mounted slow marine diesel engines with uneven number of cylinders(4). G 1 600 1 600 Crankshaft/drives of rigidly mounted large two-cycle engines G 630 630 Crankshaft/drives of rigidly mounted large four-cycle engines Crankshaft/drives of elastically mounted marine diesel engines G 250 250 Crankshaft/drives of rigidly mounted fast four-cylinder diesel engines(4). G 100 100 Crankshaft/drives of fast diesel engines with six or more cylinders(4). Complete engines (gasoline or diesel) for cars, trucks and locomotives(5). G 40 40 Car wheels, wheel rims, wheel sets, drive shafts Crankshaft/drives of elastically mounted fast four-cycle engines with six or more cylinders(4).

5 Crankshaft/drives of engines of cars, trucks and locomotives G 16 16 Drive shafts (propeller shafts, cardan shafts) with special Requirements Parts of crushing machines Parts of agricultural machinery Individual components of engines (gasoline or diesel) for cars, trucks and locomotives Crankshaft/drives of engines with six or more cylinders under special Requirements G Parts of process plant machines Marine main turbine gears (merchant service). Centrifuge drums Paper machinery rolls; print rolls Fans Assembled aircraft gas turbine Rotors Flywheels Pump impellers Machine-tool and general machinery parts Medium and large electric armatures (of electric motors having at least 80 mm shaft height) without special Requirements Small electric armatures, often mass produced, in vibration insensitive applications and/or with vibration-isolating mountings Individual components of engines under special Requirements G Gas and steam turbines, including marine main turbines (merchant service).

6 Rigid turbo-generator Rotors Computer memory drums and discs Turbo-compressors Machine-tool drives Medium and large electric armatures with special Requirements Small electric armatures not qualifying for one or both of the conditions specified for small electric armatures of Balance Quality grade G Turbine-driven pumps G1 1 Tape recorder and phonograph (gramophone) drives Grinding-machine drives Small electric armatures with special Requirements G Spindles, discs and armatures of precision grinders Gyroscopes 1) v = 2 n/60 n/10, if n is measured in revolutions per minute and v in radians per second. 2) For allocating the permissible residual unbalance to correction planes, refer to "AIIocation of Uper to correction planes.". 3) A crankshaft/drive is an assembly which includes a crankshaft, flywheel, clutch, pulley, vibration damper, rotating portion of connecting rod, etc.

7 4) For the purposes of this part of ISO 1940/1, slow diesel engines are those with a piston velocity of less than 9 m/s; fast diesel engines are those with a piston velocity of greater than 9 m/s. 5) In complete engines, the rotor mass comprises the sum of all masses belonging to the crankshaft/drive described in note 3 above. 2. Figure 1-A Maximum permissible residual unbalance, eper (Imperial values adapted from ISO 1940/1). PERMISSIBLE RESIDUAL UNBALANCE eper in lb-in/lb of rotor weight CENTER OF GRAVITY DISPLACEMENT, eper in inches or MAXIMUM SERVICE SPEED IN RPM. 3. PERMISSIBLE RESIDUAL UNBALANCE, eper in g-mm/kg of rotor weight OR. CENTER OF GRAVITY DISPLACEMENT, eper in m 4. (From ISO 1940/1). MAXIMUM SERVICE SPEED IN RPM. Figure 1-B Maximum permissible residual unbalance, eper Balance Quality GRADES ALLOCATION OF Uper Table 1 shows the Balance Quality grades for a TO CORRECTION PLANES.

8 Variety of rotor types. The "G" number is the Uper is the total permissible residual unbalance product of specific unbalance and the angular and must be allocated to the balancing correction velocity of the rotor at maximum operating speed planes used based on rotor dimensions and and is a constant for Rotors of the same type. configuration. G = e x v = constant For Rotors balanced in a single correction plane, all of the Uper applies to that correction plane. This is based on the fact that geometrically similar Rotors running at the same speed will have similar For Rotors balanced in two correction planes, Uper stresses in the rotor and its bearings. must be allocated to each correction plane based on rotor configuration and dimensions. Balance Quality grades are separated by a factor of However, G numbers of intermediate value may be used to satisfy special Requirements .

9 For example, a standard pump impeller has a suggested Balance Quality grade of G Special conditions may require a better Balance Quality of G to satisfy installation in an area with low structure-borne noise limits. DETERMINING PERMISSIBLE. RESIDUAL UNBALANCE - Uper Uper = eper x m (m = rotor mass). Permissible residual unbalance is a function of G. number, rotor weight and maximum service speed Figure 2 Symmetrical Rotors of rotation. Instead of using the graph to look up the "specific unbalance" value for a given G SYMMETRICAL Rotors . number and service RPM and then multiplying by Rules for symmetrical Rotors . (See Figure 2.). rotor weight (taking care to use proper units), Uper can be calculated by using one of the following 1. Correction planes are between bearings. formulae: 2. Distance "b" is greater than 1/3 "d.

10 ". 3. Correction planes are equidistant from the Uper (oz-in) = x G x W/N (W in Ib) center of gravity. Uper (g-in) = x G x W/N (W in Ib) Uper left = Uper right = Uper/2. Uper (g-mm) = 9549 x G x W/N (W in kg) When correction planes are NOT equidistant from the center of gravity, then - G = Balance Quality grade from Table 1. Uper left = Uper (hR/b). W = Rotor weight Uper right = Uper (hL/b). N = Maximum service RPM The Uper left or Uper right should not be less than 30% or more than 70% Uper. If they are, then A slide rule that calculates Uper is also available use rules for narrow Rotors . from some balancing machine manufacturers. 5. Rotors WITH OUTBOARD 3. Couple corrections are made 180 apart in their CORRECTION PLANES respective planes. 4. The plane for static corrections may be a third plane or either of the planes used for couple corrections.


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