6.
VariableCondi乌ionsState expected variation in intake conditions-pressure， temperature， relativehumidity，
M认， etc.
State expected variation in discharge pressure.
乌ablecon乌inued onnex乌 page
Table 4-.con乌inued
It is extremely important that changing conditions be related to each other.
If relative humidity varies from 50 to 100% and inlet temperature varies from 0 to 100 oF
does 100% RH correspond with 100 oF?
Variations in conditions are best shown in tabular form with all conditions included in
each column.
7. Flo. Diagram
Provide a schematic flow sheet showing controls involved.
8.
Regula乌ion
认hat is to be controlled-pressure，flow， or temperature?
Advise permissible variation in controlled item.
Is regulation manual or automatic?
Ifautomatic， are operating devices andjor instruments to be included?
How many control steps are desired on a reciprocator?
9.
CoolingWa乌er
Temperature: maximum and minimum
Pressure at inlet and backpressure， if any.
认hether open or closed cooling system desired.
Source of water.
Fresh，sale， or brackish.
Silty or corrosive.
10. Driver Specify type of driver.Electric motor:type， currentconditions， powerfactor， enclosure， servicefactor，temperaturerise， ambient temperature.Steam: inlet and exhaustpressure， inlet temperature andquality， importance of minimum water rate.Fuel gas: gasanalysis， availablepressure， low heating value of gas. Geared: AGMA rating if special.
11. General Acceptability of petroleum lubricants? Indoor or outdoor installation?Floorspace， special shape? Provide a sketch. Soil character. List accessories desired and advise which are to be spared. Pulsation dampeners or intake or discharge silencers to be supplied.
12.
Specifica乌ions Provide each bidder with three copies of any specification for the particular project. complete information enables all manufacturers to bid competitively on the same basis and assists the purchaser in evaluating bids.
be supplied to thevendor， while the important points to consider in evaluat-ing centrifugal compressors are listed in Table 4-4. These tables will enable the engineer to make a proper evaluation of each critical point and ensure that he is purchasing units of high reliability and efficiency.
Table 4-4 Points to .onsider in a .entrifugal .ompressor
1. Number of stages
2. Pressure ratio and mass flow (per casing)
3. Type of gas seals (inner seal) and oil seals
4. Type of bearings (radial)
5. Bearing stiffness coefficients
6.Types
of thrust bearings (Taperedland， nonequalizing tilting pad and .ingsbury)
7. Thrust float
8. Temperature for journal and thrust bearings (operating temperature)
9. critical speed diagram (Speed versus bearing stiffness curve)
10. Type of impeller
a. Shroud or unshrouded
b. Blading
c. Attachment of blades to hub and shroud
11. Attachment of impellers to shaft
a. Shrink fit
b. .ey fit
c. Other
12. campbell diagrams of impellers
a. No. of blades (impellers)
b. No. of blades (diffuser)
c. No. of blades (guide vanes)
13. Balance piston
14. Balance planes (location)
a. How is it balanced (detail)
15.认eight of toros (assembled)
a. Split casing
b. Barrel
16. Data on torsional vibration (Bending criticals)
17. Alignment data
18. Type of coupling between tandems
19. Performance curves (separate casings)
a. Surge margin
b. Surge line
c. Aerodynamic speed
d. Efficiency
20. Intercooling type of cooler
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