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Differential Meter (Square Root Meter) Calibration & Training Services

Differential meters refer to any meter that uses an obstruction in the flow to create a differential pressure. Any differential meter uses calculations based on the Bernoulli Principle. The Bernoulli Principle states that there is a relationship between the pressure in the pipe and the velocity of the flowing fluid. The primary differential producer provides a restriction in the flowing area that causes the fluid to accelerate. This acceleration can be measured by measuring the pressure drop across the differential producer. There are several important components of differential metering system. The actual meter is not just the differential producer, but includes the upstream and downstream lengths as well as any taps, thermowells, and flow conditioners. Other components in a differential measurement system include pressure and differential sensors (transducers), RTDs, and flow computers. All components of a differential flow measurement system must be evaluated when evaluating the system. Major benefits to using differential producing meters include reliability and repeatability.

Subsonic venturi meter   Cone meter

CEESI has been instrumental in the research and development of differential producing meters. For meters like orifice meters, venturi meters, and nozzles, there is not a need to flow calibrate each individual meter, provided the metering system is in compliance with applicable industry standards. The uncertainty associated with using these in compliance with a standard is on the order of 0.5 – 1.5%. Reduced uncertainties may be obtained by calibrating the actual meter run and/or system. For other meters, it is imperative to calibrate each individual meter. There is a standard for a testing protocol for differential type meters. API MPMS 22.2 provides guidance for what data needs to be taken in order to properly identify the performance of a differential producing meter. Several meters have undergone enough testing to be included in the Bureau of Land Management Uncertainty Calculator.

CEESI has performed testing and calibration on the following meter types:
  • Brandt Tube™
  • Cameron NUFLO™ Differential Pressure Cone Meter™
  • Dynamic Flow Computers SmartCone Meter™
  • Elbow Meter
  • Laminer Flow Element
  • McCrometer V-Cone Meter™
  • McCrometer Wafer Cone Meter™
  • Orifice Meter
  • Pitot Tubes
  • Self Averaging Pitot Tube
  • Subsonic Flow Nozzle
  • Subsonic Venturi Meters
  • Rosemount Annubar Meter™
  • Rosemount Conditioning Orifice Plate Meter™
  • Veris Accelabar Meter™
  • Veris Verabar Meter™
  • Wedge Meters

Differential Meter Services

  • Calibration of Line Sizes from 3/4” to 36”
  • Capable of reaching flowrates over 1 Billion Cubic Feet per Day (BCFD) in Natural Gas
  • Typical uncertainties for differential meter calibration are 0.23% in Iowa, and less than 0.5% in Colorado
  • Flow computer testing and verification
  • API MPMS 22.2 Testing
  • Flow conditioner testing
  • Consulting on differential meter station design
  • Consulting for differential flow measurement discrepancies
  • On-site auditing of differential metering setups
  • On-site differential meter validation
  • Training on fundamentals of differential meters
  • Training on advanced differential metering topics
Request a quote or contact us if you have questions about differential meter calibrations.

Sample Differential Meter Calibration Certificates

Differential Meter-specific Training Courses & Events

Differential Meter Standards

Some of the standards for differential meters include:
  • AGA Report Number 3
  • API Manual of Petroleum Measurement Standards (MPMS) Chapter 14.3
  • ISO 2186 (Connections to secondary devices)
  • ISO 15377
  • ISO 3966
  • ISO 7194
  • ISO 5167
  • ASME MFC 14M (Small bore orifice meters)
  • API MPMS Chapter 21 (Flow Computers)
  • API MPMS Chapter 22.4 (Differential Pressure, Pressure, and Temperature Measurement)
  • API MPMS Chapter 22.5 (Flow Computers)

Differential Meter Publications & Papers

The following is a random sampling of documents relating to differential flowmeters from the Flow Measurement Technical Library. This library contains over 68,000 documents on flow measurement from NIST, ISHM, AGA, ISFFM, ASGMT, FLOMEKO, MSC and others; thousands of these documents are available for free download.

John Garnett,  1987
Abstract: Insertion flow meters, as typified by averaging pitot tubes, vortex shedders and insertion turbines, should be considered for measurement points throughout the hydrocarbon industry. They can offer real advantages, particularly economic, when applied properly. Averaging pitot tubes will be discussed in detail because they also offer many of the benefits of head-type devices.

FLOW-DYNE Engineering, Inc.,  1972
Abstract: The venturi flow meter is installed as a section of pipe or tubing and is used to measure the flow of fluids, either gaseous or liquid. The meter consists of a converging inlet section, a short straight throat section, and a diverging section. As the fluid enters the converging section, its velocity begins to increase, reaching a maximum value at the throat. The diverging section then slows the fluid to approximately its original value. At the point of maximum velocity, the static pre ....

J. M. Robertson, M. E. Clark,  1977
Abstract: Reliable and accurate flow measurements in large pipes are becoming increasingly important in assessing the performance of power plant equipment in these days of energy crises. Since the Pitot-static tubes that are used for the determination of flows in large (diameters from 4 to 8 ft) pipes are being calibrated in a smaller (24-in.) pipe, various uncertainties arise in the use of the Pitot and in the interpretation of its coefficient. These uncertainties include the correction for the ar ....

M. J. Reader-Harris, W. C. Brunton, J. J Gibson, D. Hodges, I. G. Nicholson,  1999
Abstract: This paper describes 15 Venturi tubes manufactured in a range of diameters from 50 mm to 200 mm and of diameter ratios from 0.4 to 0.75. They have been calibrated in water and high-pressure air. An equation for the discharge coefficient in water has been obtained with an uncertainty of 0.75 per cent. In air the situation is considerably more complicated. Equations fitting all the air data with an uncertainty of approximately 1.25 per cent have been derived. Of these equations the one with a phys ....

Search the Flow Measurement Technical Library for papers on differential meters.

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