ASME PTC

The mercury barometer (Fig. 10-11) indicates directly the absolute pressure of the atmosphere in terms of height of the mercuiy column. Normal (standard) barometric pressure is 101.325 kPa by definition. Equivalents of this pressure in other units are 760 mm mercury (at 0°C), 29.921 iuHg (at 0°C), 14.696 IbFin, and 1 atm. For cases in which barometer readings, when expressed by the height of a mercuiy column, must be corrected to standard temperature (usually 0°C), appropriate temperature correction factors are given in ASME PTC, op. cit., pp. 23-26 and Weast, Handbook of Chemistty and Physics, 59th ed., Chemical Rubber, Cleveland, 1978-1979, pp. E39-E41. 

Venturi Meters The standard Herschel-type venturi meter consists of a short length of straight tubing connected at either end to the pipe line by conic sections (see Fig. 10-15). Recommended proportions (ASME PTC, op. cit., p. 17) are entrance cone angle Oti = 21 2°, exit cone angle Cto = 5 to 15°, throat length = one throat diameter, and upstream tap located 0.25 to 0.5 pipe diameter upstream of the entrance cone. The straight and conical sections should be joined by smooth cui ved surfaces for best results. 

Value of the discharge coefficient C for a Herschel-type venturi meter depends upon the Reynolds number and to a minor extent upon the size of the venturi, increasing with diameter. A plot of C versus pipe Reynolds number is given in ASME PTC, op. cit., p. 19. A value of 0.984 can be used for pipe Reynolds numbers larger than 200,000. 

Flow Nozzles A simple form of flow nozzle is shown in Fig. 10-17. It consists essentially of a short cylinder with a flared approach section. The approach cross section is preferably elliptical in shape but may be conical. Recommended contours for long-radius flow nozzles are given in ASME PTC, op. cit., p. 13. In general, the length of the straight portion of the throat is about one-h f throat diameter, the upstream pressure tap is located about one pipe diameter from the nozzle inlet face, and the downstream pressure tap about one-half pipe diameter from the inlet face. For subsonic flow, the pressures at points 2 and 3 will be practically identical. If a conical inlet is preferred, the inlet and throat geometry specified for a Herschel-type venturi meter can be used, omitting the expansion section. 

Sinee there is no standard eode whieh governs the testing of hot gas expanders, related or otherwise applieable eode praetiees should be used whenever possible. Thus, the relevant portions of the ASME PTC-6 and ASME PTC-IO-ABCD should be eonsidered. In partieular, attention should be given to the paragraphs relating to aeeuraey of instruments, speeifieally those in seetions 0.01 and 0.02 of PTC-6 on measurement uneertainty, whieh are quoted as follows ... 

ASME, Performance Test Code on Gas Turbines, ASME PTC 22 1997... 

Meetings should be held with all parties concerned as to how the test will be conducted and an uncertainty analysis should be performed prior to the test. The overall test uncertainty will vary because of the differences in the scope of supply, fuel(s) used, and driven equipment characteristics. The code establishes a limit for the uncertainty of each measurement required the overall uncertainty is then calculated in accordance with the procedures defined in the code and by ASME PTC 19.1. 

The turbine undergoes three basic tests, these are hydrostatic, mechanical, and performance. Hydrostatic tests are to be conducted on pressure-containing parts with water at least one-and-a-half times the maximum operating pressure. The mechanical run tests are to be conducted for at least a period of four hours at maximum continuous speed. This test is usually done at no-load conditions. It checks out the bearing performance and vibration levels as well as overall mechanical operability. It is suggested that the user have a representative at this test to tape record as much of the data as possible. The data are helpful in further evaluation of the unit or can be used as base-line data. Performance tests should be conducted at maximum power with normal fuel composition. The tests should be conducted in accordance with ASME PTC-22, which is described in more detail in Chapter 20. 

ASME, Perfomiaiice Test Code on Overall Plant Performance, ASME PTC 46 1996. 

The ASME, Performance Test Code on Overall Plant Performance, ASME PTC 46, was designed to determine the performance of the entire heat cycle as an integrated system. This code provides explicit procedures to determination of power plant thermal performance and electrical output. 

The PTC 22 establishes a limit of uncertainty of each measurement required the overall uncertainty must then be calculated in accordance with the procedures defined in ASME PTC 19.1 Measurement Uncertainty. The code requires that the typical uncertainties be within a 1.1% for the Power Output, and 0.9% in the heat rate calculations. It is very important that the post-test uncertainty analysis should be also performed to assure the parties that the actual test has met the requirement of the code. 

The instrumentation will be calibrated as per the requirements of the test codes. All the instrumentation must be calibrated before a test and certified that they meet the code requirements. The ASME PTC 19 series outlines the governing requirements of all instrumentation for an ASME Performance Test to be within the governing band of uncertainty. 

Table 20-1 is a very short abstract of the test measurement requirements for the performance tests the ASME PTC 19 series should be the final governing document ... 

Correction factors are also provided in ASME PTC Test Code-46. The correction factors for ambient temperature, ambient pressure, and relative humidity are presented in this chapter. 

The ASME, Performanee Test Code on Gas Turbines, ASME PTC 22 examines the overall performanee of the gas turbine. The ASME PTC 22 only examines the overall turbine and many turbines in the field are better instrumented for eomputation of the detail eharaeteristies of the gas turbine. Figure 20-6 shows the desired loeation of the measurement points for a fully instrumented turbine. The following are the various eomputations required to ealeulate the gas turbine overall performanee based on the eode ... 

ASME, Performanee Test Code on Gas Turbine Eleat Reeovery Steam Generators, ASME PTC 4.4 1981, Ameriean Soeiety of Meehanieal Engineers, Reaffirmed 1992... 

The basis for code testing is the ASME Power Test Code, PTC 10 11 [ or ASME PTC 9 [2] as applicable. Several specific points made in the code were intended as guiding principles, yet are often misunderstood. The following facts must be eonsidered. 

Part of the planning should include the evaluation of test uncertainty. This evaluation can be limited to a common sense approach based on available instrumentation and the locations relative to the ideal. A more sophisticated study can be made in which instrumentation accuracy and the impact of any inaccuracy on the measured parameters is evaluated. This is a complex task with the need being based on the motivation for the test. If the test is being performed to settle a dispute, a formal understanding of the uncertainty should be developed. Methods for evaluation of test uncertainty are found in ANSI/ASME PTC 19.1 [11]. 

Compressors and Exhausters, ASME PTC 10-1965, New York Ameri-c,iti Society of Mechanical Engineers, 1965. 

Displacement Compressors, Vacuum Pumps and Blowers, ASME PTC 9-1970, ANSI PTC 9-1974, New York American Society of Mechanical Elngineers, 1970. New York American National Standards Institute, 1974,... 

Flow Measurement, Chapter 4, Instruments and Apparatus, ASME PTC 19.5 4-1959, New York American Society of Mechanical Engineers, 19.59. 

ASME PTC 50 ASME Performance Test Code 50 - Fuel Cell Power Systems provides test procedures, methods and definitions for the performance characterization of fuel cell power systems. The code specifies the methods and procedures for conducting and reporting fuel cell system ratings. Specific methods of testing, instrumentation, techniques, calculations and reporting are presented. This standard is currently being drafted and is expected to be approved and published in 2002. 

Tube Size for Manometers To avoid capillary error, tube diameter should be sufficiently large and the manometric fluids of such densities that the effect of capillarity is negligible in comparison with the gauge reading. The effect of capillarity is practically neghgible for tubes with inside diameters 12.7 mm (% in) or larger (see ASME PTC, op. cit., p. 15). Small diameters are generally permissible for U tubes because the capillary displacement in one leg tends to cancel that in the other. 

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