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Title: Field pressure measurements, Fort Peck powerhouse penstock, Fort Peck, Montana
Authors: United States. Mississippi River Commission.
U.S. Army Engineer Waterways Experiment Station.
Keywords: Hydrostatic pressure--Measurement
Hydroelectric power plants--Montana--Safety measures
Fort Peck Dam (Mont.)
Publisher: U.S. Army Engineer Waterways Experiment Station.
Engineer Research and Development Center (U.S.)
Description: Technical memorandum
Synopsis: This memorandum constitutes a comprehensive report on pressure measurements in the penstock of the Fort Peck power plant made by personnel of the U. S. Waterways Experiment Station, Vicksburg, Mississippi, for the purpose of determining a safe operating procedure for the power plant equipment under the unusual conditions created through omission of a surge tank in the installation. This investigation was authorized 31 May 1943 by the District Engineer at Fort Peck, Montana, at which time it was requested that the Experiment Station furnish personnel and equipment for making these measurements. Materials for construction of surge tanks as planned for the Fort Peck powerhouse were not procurable due to war conditions. Since this usual adjunct to hydroelectric power systems was eliminated at this power plant, it was considered desirable to measure the amplitude of the pressure surges in the penstock in order that design pressures not be exceeded. The determination of a safe operating procedure primarily required data concerning penstock surge pressures, turbine speed, and generator output under typical severe operating conditions. Elimination o' the surge tank required a lengthening of the gate closure time in order that excessive pressures not be produced in the penstock; on the other hand, this slower shutdown time created potentially hazardous runaway conditions, as a solution for which a water rheostat was developed to carry the generator output during the period in which the unit was closing down. The testing and calibration of this water rheostat was an important part of the testing program. In addition, certain other measurements were made which were incidental to the task of testing and putting this new plant into operation, such as penstock strain measurements and oscillographic studies of generator voltage and current interruptions during faulty circuit breaker operation. The instrumentation required for making these measurements included specially-built hydrostatic pressure cells with a range of 0 to 150 psi, wire-type strain gauges for penstock strain measurements, a Whittemore strain gauge for checking longitudinal slippage across a riveted circumferential joint, a gate-position indicator system, a 5- ampere shunt for recording generator current, a current-limiting resistor for recording generator voltage, a balancing and calibrating panel for the pressure cells, a four-channel, high-gain amplifier for use with the pressure cells and strain measurements, and a Westinghouse seven-element oscillograph and camera, together with considerable accessory equipment such as an oscillator, power pack, constant-voltage transformer, timing-wave transformer, and shunt panel. As a result of the pressure surge measurements, a satisfactory gate closure time was determined. Oscillograms showing loss of line load and transfer of line load to water rheostat were obtained which depict clearly the results to be expected under these two conditions of operation, and curves of generator overspeed, generator output, and penstock pressure are presented for various operating conditions. The maximum pressure head observed on the penstock during the tests was approximately 230 ft; this is well below the 300 ft maximum head for which the penstock was designed. The time constant (41/a) for the penstock was determined to be 3.50, which checks closely with the computed value longitudinal slippage across a circumferential joint was determined to· be negligible, and circumferential strain measurements were found to agree closely with design values.
Rights: Approved for public release; distribution is unlimited.
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