43- .MEASURING OF AIR. 



be always remembered that it can only give correct results as 

 long as yr) is sufficiently small to allow the third and following 

 terms of the series used in deriving the formula to be neglected. 



In the following the theoretical statements given before will 

 be applied to two Tests made on high power air compressors, 

 the one being an electrically driven turbo-compressor the other 

 one a steam driven reciprocating compressor. 



1 ; .' (I.) TURBO COMPRESSOR TEST. 



This test was made on June 9th, 1912, on the Pakorny and 

 AVittekind compressor at the Robinson Compressor Station of 

 the Victoria Falls and Transvaal Power Co. Ltd. The com- 

 pressor delivers approximately 20 lbs. of air per second or 21,500 

 cu. it. of free air per minute at a pressure of 9 atmospheres 

 absolute (128 lbs. abs. ) and recjuires 3,000 K.A\'. electric input 

 to the motors. 



In order to secure that the Compressor was run at steady 

 loads during each test and to enable these loaas to be varied 

 \oluntarily, the section of the pipe line from Robinson Com- 

 ])ressor Station westwards to the first valve pit at " X " (about 

 1,000 yards) was isolated and a cover removed from the water 

 collector about 300 yards from the Station. The discharge from 

 the Compressor was throttled at the valves near the Station to 

 secure the desired pressure on the machine and the whole dis- 

 charge took place noiselessly through the water collector. 



The compressor was tested under ordinary working con- 

 ditions and was not cleaned or specially prepared in any way for 

 the test. It had been cleaned so far as the intercooler and jackets 

 were concerned on December nth, 191 t. Since that date it had 

 run on load for 2,600 hours and had been standing for 2,100 

 hours. It had been previously in use after erection for 1,100 

 hours out of 2,600 hours. 



The compressor was started up about 7. a.m. running lightly 

 loaded for an hour, after which normal load was put on. The 

 first set of measurements commenced at 10.05 ^•^'^"'- The first 

 test was run for an hour, the second, third and fourth for 40 

 minutes each and the fifth and last test for 30 minutes. Between 

 the second and third tests there was an interval of one hour and 

 a half during which time the machine was kept running at full 

 load. The readings taken on each test show the extent to which 

 the conditions were steady. 



All instruments were specially calibrated before the test. 

 Measurements of air pressure were made whenever possible by 

 means of water or mercury manometers, but in the cases of the 

 highest pressures, where spring controlled gauges had to 'be used, 

 these were carefully compared with a standard gauge that had 

 itself been calibrated with a dead-weight tester. 



