ASME Throat Tap Nozzle

ASME PTC 19.5 Throat Tap Nozzle

+/- 0.70% Uncalibrated Uncertainty
High Accuracy

  • Line size: 4 to 28 inches
  • Head Loss (permanent pressure loss) in % of Differential: 60% to 85% (18% to 25% with optional outlet diffuser cone), Beta Dependent
  • Recommended Application, THROAT Reynolds Number: Greater than 500,000 for basic accuracy


The ASME Throat Tap Flow Nozzle provides high accuracy and precision which is used for the testing of steam turbine efficiency as prescribed in the ASME PTC-6 2004 Performance Test Code. The difference between a standard ASME Throat Tap nozzle and a PTC-6 Flow Nozzle is there is more flexibility in application and calibration with a standard ASME Throat Tap Nozzle. A standard Throat Tap Nozzle is recommended to be processed the same as a PTC-6 nozzle, but it is not required. IE, calibration is optional and up/down spools and other components are also optional.


Standard Line Size
4 to 28 inches (not limited to)
Head Loss (permanent pressure loss) in % of Differential
60% to 85% (18% to 25% with optional outlet diffuser cone), Beta Dependent
Basic Accuracy (% of Total)
[Calibrated +/- 0.25%] [Uncalibrated +/- 0.70%]
Recommended Application, THROAT Reynolds Number
Greater than 500,000
Recommended Straight Piping
20D Upstream / 10 D Downstream
Recommended Beta Range
0.25 through 0.50
Useful Service Life
Medium to Long
Service Functional Limits
Clear Liquids, Gas and Steam
Clear Liquids, Gas and Steam
Common Materials
Carbon Steel, Stainless Steel, Chrome Moly
Other Available Materials not limited to
Aluminum, Zirconium, Hastelloy, Monel, Duplex SS, Titanium, Tantalum, 321SS
The ASME Throat Tap Nozzle has the advantage of being used in applications outside of the typical turbine performance test application. This carries the benefit of maintaining high accuracy flow measurement without the stringent requirements associated with formal performance tests.

Support and Service

In addition to a wide range of differential producing Venturi flow meters, orifice plates, WedgeType™ flow meters, and open channel flow elements, PFS provides comprehensive, specialized services for new and existing flow meters, including rehabilitation, hydraulic analysis, and full engineering support.


ISO 9001, ASME S&U, PED Certified, CRN.

See all certifications