In view of the great importance he must attach to his gage readings, the tester would do well to test and calibrate and adjust where necessary all the gages he intends using during a test. This he can do with a standard gage-testing outfit. By this means only can he have full confidence in the accuracy of his results.

In like manner it is his duty personally to supervise the connecting and arrangement of the gages, and the preliminary testing for leakage which can be carried out simultaneously with the vacuum test made upon the turbine casing.

Where Thermometers are Required

Equally important with the foregoing is the necessity of calibrating and testing of all thermometers used during a test. Where possible it is advisable to place new thermometers which have been previously tested at all points of high temperature. Briefly running them over, the points at which it is necessary to place thermometers in the entire system of the steam and condensing plant are as follows:

  1. (1) A thermometer in the steam pipe on the boiler, where the pipe leaves the superheater.
  2. (2) In the steam pipe immediately in front of the main stop-valve, near point E in Fig. [75].
  3. (3) In the main governing valve body (see I, Fig. [75]) on the inlet side.
  4. (4) In the main governing valve body on the turbine side, which will register temperatures of steam after it has passed through the valve.
  5. (5) In the steam-turbine high-pressure chamber, giving the temperature of the steam before it has passed through any blades.
  6. (6) In the exhaust chamber, giving the temperature of steam on leaving the last row of blades.
  7. (7) In the exhaust pipe near the condenser.
  8. (8) In the condenser body.
  9. (9) In the circulating-water inlet pipe close to the condenser.
  10. (10) In the circulating-water outlet pipe close to the condenser.
  11. (11) In the air-pump suction pipe close to the condenser.
  12. (12) In the air-pump suction pipe close to the air pump.

It is not advisable to place at those vital points, the readings at which directly or indirectly affect the consumption, two thermometers, say one ordinary chemical thermometer and one thermometer of the gage type, thus eliminating the possibility of any doubt which might exist were only one thermometer placed there.

There is no apparent reason why one should attempt to take a series of temperature readings during a consumption test on varying load. The temperatures registered under a steady load test can be obtained with great reliability, but on a varying load, with constantly changing temperatures at all points, this is impossible. This is, of course, owing to the natural sluggishness of the temperature-recording instruments, of whatever class they belong to, in responding to changes of condition. As a matter of fact, the possibility of obtaining correctly the entire conditions in a system running under greatly varying loads is very doubtful indeed, and consequently great reliance cannot be placed upon figures obtained under such conditions.

A few simple calculations will reveal to the tester his special requirements in the direction of measuring tanks, piping, etc., for his steam consumption test. Thus, assuming the turbine to be tested to be of 3000 kilowatt capacity normal load, with a guaranteed steam consumption of, say, 14.5 pounds per kilowatt-hour, he calculates the total water rate per hour, which in this case would be 43,500 pounds, and designs his weighing or measuring tanks to cope with that amount, allowing, of course, a marginal tank volume for overload requirements.