APPENDIX III 789 



apply to the point of measurement in the tailrace; that is, the velocity 

 head at the point of measurement in the tailrace shall be added to the actual 

 elevation of the surface, the sum being considered the equivalent still-water 

 elevation. 



Except where specifically stated herein, this code shall be understood 

 to apply to tests of the turbine proper, and the terms power, efficiency, 

 effective head, etc., are to be taken as referring to the turbine. In com- 

 puting the efficiency of the turbine, the losses through the racks, in the 

 intake to the penstocks, and in the penstocks shall not be charged against 

 the turbine; nor shall the head necessary to set up the velocity required to 

 discharge the water from the end of the draft tube be charged against the 

 turbine. The net or effective head acting no the turbine shall be measured 

 from a point near the intake to the turbine casing in turbines equipped with 

 casings, or from a point immediately over the turbine in turbines having an 

 open-flume setting, to a point hi the tailrace in the manner set forth below 

 under the heading "Measurement of Head." Since the turbine cannot 

 develop power without discharging water, a correction for the velocity head 

 required to discharge the water into the tailrace shall be added to the tail- 

 water elevation; and a similar correction applied at the intake to encased 

 turbines, as called for under the heading "Measurement of Head." The 

 power developed by the turbine shall be taken as the mechanical power 

 delivered on the turbine shaft and transmitted by the turbine shaft to the 

 generator or other driven machine or system. 



In drawing up a general code it is recognized that under particular cir- 

 cumstances sometimes occurring, methods of measuring or computing certain 

 factors entering into the test different from those specified, may appear pos- 

 sible and reasonable; it is, however, the intent of this code that the meaning 

 of the terms efficiency, effective head, etc., shall be the efficiency, effective 

 head, etc., determined as herein specified, and that such terms shall be under- 

 stood only as thus defined. 



GENERAL 



3. Inspection. Careful inspection should be made before, during, and 

 after the tests to insure the proper operation of the turbine and conditions 

 of measurement. 



The turbine runner, guide vanes, and casing should be inspected before 

 and after test to guard against obstructions clogging the vanes. Any change 

 in performance during a test should be investigated. 



4. Operating Conditions During Test. Apparatus installed for the pur- 

 pose of the test shall not affect the performance of the turbine during 

 the test. When any doubt exists regarding this point, a special experiment 

 shall be carried out to detect any effect of removing and replacing the 

 apparatus in question, other conditions being maintained constant. 



The unit shall be in normal operating condition throughout the test, 

 and shall have been operated under load for an aggregate time of at least 

 three days prior to the test. 



4. (a) Leakage. Care should be taken that all air inlets into the draft 

 tube are closed, and that leakage of air into the tube or drawing of air into 



