Before diving into the "Fixed" aspect, let us establish the foundation. ASME PTC 19.2 is a standard published by the American Society of Mechanical Engineers (ASME) under the Performance Test Codes (PTC) umbrella. Its full title is "Pressure Measurement Instruments and Apparatus."
This code provides uniform methods for the testing and calibration of pressure measuring devices. It applies to:
The standard ensures that when an engineer reports a pressure reading during a performance test (e.g., turbine efficiency, pump flow, boiler output), the measurement uncertainty is known, quantified, and consistent with industry best practices. asme ptc 192 fixed
ASME PTC 19.2 does not set a limit. Deadweight testers exist from vacuum to 60,000 psi (400 MPa). However, at very high pressures, piston-cylinder elastic deformation must be accounted for.
In the field of thermodynamic testing, pressure is a secondary measurement—its value is used to derive primary performance metrics such as power output, heat rate, efficiency, and flow rate (via ASME PTC 6 or 19.5). Consequently, small errors in pressure measurement propagate into significant uncertainties in final results. Before diving into the "Fixed" aspect, let us
ASME PTC 19.2 – “Pressure Measurement” (most recently reaffirmed with updates reflecting modern instrumentation) categorizes pressure measurement systems into distinct classes based on their intended use and permanence. Among these, the Fixed installation is the most robust and accurate, intended for long-term, high-importance monitoring or code-compliant acceptance testing.
No. The Fixed method as described in ASME PTC 19.2 applies only to positive gauge pressures. For absolute or vacuum, you need a different setup (e.g., piston gauge with vacuum chamber or comparison method with barometric reference). The standard ensures that when an engineer reports
To comply with the standard, a fixed pressure tap must meet specific geometric and installation criteria. Violating any of these rules introduces systematic uncertainty that cannot be calibrated out.
The ASME PTC 19.2 Fixed method is preferred in scenarios where:
The term "fixed" also implies that the sensor is permanently hard-piped to the tap. ASME PTC 19.2 specifies:
No. The deadweight tester must have documented traceability for its masses and piston area. Many low-cost testers lack proper certification. ASME PTC 19.2 requires that the tester’s effective area be determined by an accredited laboratory at least every 2 years.