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Excitation sources， which should be included in the campbell diagrams， should include fundamental and first harmonic passing frequencies of rotat-ing and stationary blades upstream and downstream of each bladerow， gaspassage splitters， irregularities in vane and nozzle pitch at horizontal casingflanges， the first 10 rotor speed harmonics， meshing frequencies in gearunits， and periodic impulses caused by the combustor arrangement.
The turbine undergoes three basictests， these are hydrostatic， mechan-ical， and performance. Hydrostatic tests are to be conducted on pressure-containing parts with water at least one-and-a-half times the maximum operating pressure. The mechanical run tests are to be conducted for at least a period of four hours at maximum continuous speed. This test is usually done at no-load conditions. It checks out the bearing performance and vibration levels as well as overall mechanical operability. It is suggested that the user have a representative at this test to tape record as much of the data as possible. The data are helpful in further evaluation of the unit or can be used as base-line data. Performance tests should be conducted at maximum power with normal fuel composition. The tests should be con-ducted inaccordance with ASME PTc-22， which is described in more detail in chapter 20.
Gears
This standard API Standard 613 covers special purpose gears. They aredefined asgears， which have either or both actual pinion speeds of more than 2900 rpm and pitchline velocities of more than 5000 ftjmin (27 metersjsec). The standard applies to helical gears employed in speed-reducer or speed-increaser units.
The scope and terms used are well defined and includes a listing of standards and codes for reference. The purchaser is required to make deci-sions regarding gear-rated horsepower and rated input and output speeds.
This standard includes basic design information and is related to AGMA Standard 421. Specifications for cooling water systems are given as well as information about shaft assembly designation and shaft rotation. Gear-rated power is the maximum power capability of the driver. Normally， the horsepower rating for gear units between a driver and a driven unit would be 110% of the maximum power required by the driven unit or 110% of themaximum power of thedriver， whichever is greater.
The tooth pitting index or K factor is defined as
W(R +1)
K二烏 x(4-4)
F xdR
where:
W烏二transmitted tangentialload， in pounds at the operating
pitch diameter
12， 600 xGear rated horse power

W烏二 Pinion rpm xd
F二net face width， inches
d二pinion pitch diameter， inches
R二ratio (number teeth in gear divided by number teeth in pinion)
The allowable K factor is given by
Allowable K二Material index numberjService factor (4-5)
Service factors and material index number tabulation are provided forvarious typical applications， allowing the determination of the K factor. Gear tooth size and geometry are selected so that bending stresses do not exceed certain limits. The bending stress number is given by
S烏二Bending stress number
   
二 烏Wx生nd x(SF)x 1.8 cos旦(4-6)F與
where:
W
烏二as defined in Equation (4-4)
生nd二normal diametral pitch
F二net facewidth， inches
旦二helix angle
與二geometry factor (from AGMA 226)
SF二service factor
Design parameters on casings， joint supports， and bolting methods. Some service and size criteria are included.
critical speeds correspond to the natural frequencies of the gears and the rotor bearings support system. A determination of the critical speed is made by knowing the natural frequency of the system and the forcing function.Typical forcing functions are caused by rotorunbalance， oil filters， misalign-ment， and a synchronous whirl.
Gear elements must be multiplane and dynamically balanced.認here keysare used in couplings， half keys must be in place. The maximum allowable unbalanced force at maximum continuous speed should not exceed 10% of static weight load on the journal. The maximum allowable residual unbalance in the plane of each journal is calculated using the following relationship
　
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