TP031
Performance Acceptance Test For A Non-Condensing
Extraction Turbine Generator Drive Superheated Inlet
J. Lamberson
R. Moll
Dresser-Rand, Wellsville, N.Y., USA
The test procedure that follows is intended to convey Dresser-Rand's position to customers in regard to field
performance acceptance testing. The instrumentation required for the Dresser-Rand test is less costly and
fewer component readings are required as compared to a PTC-6 high accuracy performance acceptance test.
This in no way diminishes the importance or the necessity of the PTC-6 documents, for all steam turbine testing
compiled by United States manufacturers will reference these procedures to some degree.
INTRODUCTION
The following document is a simplified ASME performance test procedure which Dresser-Rand believes is
satisfactory for the majority of non-condensing extraction turbines. The instrumentation required for this test is
much less costly, and fewer component readings are needed to obtain good results as compared to a full ASME
PTC6 test. In this simplified test, only the quantities necessary to establish the actual power output will be
measured. Reducing the amount of measurement devices does not eliminate the requirement for proper device
installation. Drawing CB-182930-K indicates placement and maximum allowable uncertainty of all necessary
instrumentation which should be calibrated before and after the test. (This procedure generally follows the
guidelines of PTC-6.)
TIMING AND DURATION OF TEST
The test should be conducted as soon as possible after initial operation under load, but no longer than 90 days.
If this timing is impossible to achieve, the test may be run immediately after the first complete inspection. At this
time, the manufacturer and the customer must both agree that the turbine and generator are in "like new"
condition for a proper acceptance test.
The test should be conducted for a two hour period. If inconsistencies appear during this duration, the source of
these variations should be located, the problem rectified, and the test should be restarted.
PERMISSIBLE DEVIATION OF VARIABLES*
Variable
1 Initial Steam Pressure
2 Initial Steam Temperature
3 Primary Flow
4 Extraction Steam Pressure
5 Exhaust Pressure
6 Speed
Deviation
±5.0% of absolute pressure
±30°F
±8.0% of guarantee
±5.0% of absolute pressure
±3.0% of the absolute pressure
±5%
An effort should be made to operate the turbine at specified contract conditions with constant load. To achieve
minimum load deviation, running the test at the valves wide open position is desirable.
*Turbine mechanical limits should not be exceeded.
PRIMARY FLOW MEASUREMENT
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Figure 1
Note 1 Figure taken from PTC-6-1976.
Note 2 Beta ratio (d/D) must have range of .25 to .5.
Note 3 A diffuser on the downstream side of the nozzle will greatly decrease the pressure loss.
Note 4 Flow nozzle should be calibrated prior to installation and visually inspected before and after the test.
Note 5 Flow straightener shall have a minimum of 30 tubes.
Figure 1 shows the required arrangement for measuring steam or water flow. It is recommended that boiler
feedwater flow be utilized rather than steam since better accuracy is achievable when the medium is a liquid. A
first stage pressure versus primary steam flow curve is a good tool to use for double checking the inlet flow
meter reading. This curve will be supplied by Dresser-Rand and is normally accurate to within 2.0% when the
machine is in new condition. The end gland leakage flow values will also be supplied by Dresser-Rand.
Primary flow measurements are to be taken at no greater interval than one minute during the test.
MEASUREMENT OF PRESSURES
A calibrated test Bourdon gauge may be used for pressures above 35 psia; for pressures below 35 psia, a
calibrated absolute pressure transducer should be utilized.
The initial steam pressure indicator should be in the steam line as close as possible to the trip and throttle valve
on the upstream side. All pressure readings should be taken upstream of any flow disturber (thermowells,
elbows, etc.) and in a straight section of pipe. The steam strainer should be known to be clean by placing a
gauge downstream of the T[T valve and reading differential pressure. Extraction and exhaust pressure should
be taken as close to the turbine as possible.
Test measurements are to be taken at a maximum interval of five minutes.
MEASUREMENT OF TEMPERATURE
Temperature should be obtained by using a continuous lead thermocouple in conjunction with a precision
potentiometer or other calibrated readout device. The initial steam temperature indicator should be in the steam
line as close as possible to the T[T valve on the upstream side. The accuracy of this temperature is very critical;
therefore, two thermocouples should be used. Each thermocouple should have its own thermometer well and
located 90 degrees apart from one another. (it may be necessary to utilize redundant temperature indicators in
other cycle locations where critical values exist.) Extraction and exhaust temperature should be taken as close
to the turbine as possible.
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The temperature element (thermocouple and well) should be immersed in the fluid a minimum of three inches
but not less than one-quarter of the pipe diameter. If the pipe is less than four inches, the element must be
arranged in such a way to allow for the minimum immersion distance.
Test measurements should be taken at a maximum interval of five (5) minutes.
MEASUREMENT OF ELECTRICAL OUTPUT
It is recommended that a three phase summing watthour meter be utilized to measure electrical output. This
value may be verified by calculating power using power factor, amp and volt readings which are available. When
using a watthour meter, the number of turns during a predetermined period of time (four minutes) must be
counted. The following example will indicate the correct procedure for determining power in KW.
Meter Constant = 45000
Number of turns in a 4 minute period = 40
PERFORMANCE RESULTS
To establish the turbine generator performance, the test power output will be compared to an analytically
predicted power based on test conditions and utilizing the same calculation method employed in the contract
performance prediction.
Correction curves for off-design conditions (pressure, temperature, etc.) will be supplied by Dresser-Rand.
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