Instrumentation & Control Engineering

Meter run

Meter Runs: Measuring the Flow of Liquids and Gases

In the realm of industrial processes, accurately measuring the flow rate of liquids and gases is crucial for efficiency, safety, and product quality. One common method employed to achieve this is through the use of meter runs.

What is a Meter Run?

A meter run, also known as an orifice meter run, is essentially a dedicated section of pipe designed to measure the flow rate of a fluid. It consists of three key components:

  • A clear run of pipe: This section of pipe must be straight and free of obstructions to ensure accurate flow measurement. The length of the straight pipe before and after the orifice plate is critical for accurate readings.
  • Orifice flanges: These flanges are attached to the pipe and provide a mounting point for the orifice plate.
  • Orifice plate: This thin, precisely machined plate with a central hole is the heart of the meter run. The size and shape of the orifice opening are calibrated to restrict the fluid flow and create a pressure differential. This differential is then measured by a differential pressure transmitter, which translates it into a flow rate reading.

How Meter Runs Work:

When fluid flows through the orifice plate, the constricted area causes a pressure drop. This pressure difference, measured between points upstream and downstream of the orifice, is directly proportional to the flow rate. The relationship between the pressure drop and flow rate is defined by a specific formula, taking into account factors like the size of the orifice, fluid density, and viscosity.

Benefits of Meter Runs:

  • Accuracy: Properly designed and installed meter runs provide highly accurate flow rate measurements.
  • Reliability: Meter runs are robust and can withstand harsh operating conditions.
  • Cost-effective: They are a relatively inexpensive method of flow measurement compared to other technologies.
  • Versatile: Meter runs can be used for a wide range of fluids, including liquids, gases, and slurries.

Applications:

Meter runs find widespread use in various industries, including:

  • Oil and gas: Monitoring the flow of crude oil, natural gas, and refined products.
  • Chemical processing: Measuring the flow of chemicals and feedstock.
  • Water and wastewater treatment: Controlling the flow of water and wastewater.
  • Food and beverage: Monitoring the flow of ingredients and finished products.

Conclusion:

Meter runs are essential tools in modern industrial processes, enabling accurate and reliable flow rate measurement. Their design, installation, and operation require careful consideration to ensure accurate and consistent readings. By understanding the fundamentals of meter runs, engineers and operators can effectively monitor and control fluid flow in various applications, optimizing efficiency and ensuring safety.


Test Your Knowledge

Meter Runs Quiz

Instructions: Choose the best answer for each question.

1. What is the primary function of a meter run? a) To measure the pressure of a fluid. b) To control the flow rate of a fluid. c) To measure the flow rate of a fluid. d) To filter impurities from a fluid.

Answer

c) To measure the flow rate of a fluid.

2. Which of the following is NOT a component of a meter run? a) Orifice plate b) Pressure transmitter c) Control valve d) Orifice flanges

Answer

c) Control valve

3. How does a meter run measure flow rate? a) By measuring the temperature of the fluid. b) By measuring the volume of the fluid. c) By measuring the pressure differential across the orifice. d) By measuring the velocity of the fluid.

Answer

c) By measuring the pressure differential across the orifice.

4. What is the main benefit of using a meter run for flow measurement? a) High cost-effectiveness. b) High accuracy and reliability. c) Ease of installation. d) Ability to measure all types of fluids.

Answer

b) High accuracy and reliability.

5. Which industry does NOT typically use meter runs for flow measurement? a) Oil and gas b) Chemical processing c) Aerospace d) Water and wastewater treatment

Answer

c) Aerospace

Meter Runs Exercise

Scenario: You are tasked with installing a meter run to measure the flow rate of natural gas in a pipeline. The pipeline has a diameter of 12 inches. You have a selection of orifice plates with different diameters.

Task: Determine the appropriate diameter of the orifice plate for the meter run. Consider the following factors:

  • Desired accuracy: The flow measurement needs to be accurate within +/- 5%.
  • Maximum flow rate: The pipeline can handle a maximum flow rate of 1000 cubic feet per minute (cfm).
  • Pressure drop: The maximum allowable pressure drop across the orifice plate is 10 psi.

Hint: Refer to standard orifice plate sizing charts or consult a flow measurement handbook for determining the appropriate orifice diameter based on the desired accuracy, flow rate, and pressure drop limitations.

Exercise Correction

This is a practical problem that requires access to specialized resources like orifice plate sizing charts or flow measurement handbooks. The solution involves finding an orifice diameter that balances the desired accuracy, maximum flow rate, and pressure drop limitations. The correct orifice diameter will depend on the specific characteristics of the natural gas and the pipeline.

**Example:** Using a chart or handbook, you might find that a 6-inch diameter orifice plate would be suitable for the given parameters. However, the specific solution will depend on the specific values you find in the reference material.


Books

  • "Flow Measurement Engineering Handbook" by R.W. Miller: A comprehensive guide to flow measurement principles, techniques, and applications, including extensive coverage of orifice meters and meter runs.
  • "Fluid Mechanics for Chemical Engineers" by J.M. Coulson, J.F. Richardson, J.R. Backhurst, and J.H. Harker: Covers the theoretical foundations of fluid mechanics relevant to understanding flow measurement, including concepts like pressure drop and flow rate.
  • "Instrumentation and Process Control" by D.M. Considine: A broad overview of instrumentation used in process industries, including detailed sections on flow measurement techniques and devices like orifice plates.

Articles

  • "Orifice Meter Design and Application" by Emerson Automation Solutions: A practical guide to designing and implementing orifice meters, including considerations for meter runs and sizing calculations.
  • "Flow Measurement with Orifice Plates: A Practical Guide" by Flow Research, Inc.: Explores the fundamentals of orifice plate flow measurement, highlighting factors influencing accuracy and the importance of proper installation.
  • "Metering Runs for Orifice Plates" by The American Society of Mechanical Engineers (ASME): Provides detailed specifications and guidelines for designing and installing meter runs according to ASME standards.

Online Resources

  • "Orifice Metering" by the National Institute of Standards and Technology (NIST): A comprehensive resource with detailed information on orifice plate theory, calibration, and measurement uncertainty.
  • "Flow Measurement Tutorial" by Omega Engineering: A practical online tutorial covering different flow measurement technologies, including orifice plates and meter runs.
  • "Metering Runs for Orifice Plates" by Emerson Automation Solutions: A technical resource offering guidelines for selecting the appropriate meter run configuration based on flow conditions and pipe size.

Search Tips

  • "Orifice meter run design" + "ASME": Search for resources that follow ASME standards for meter run design.
  • "Orifice plate installation guidelines" + "API": Explore resources that follow API (American Petroleum Institute) guidelines for orifice plate installation.
  • "Flow measurement handbook" + "pdf": Search for free downloadable flow measurement handbooks with sections on orifice plates and meter runs.
  • "Meter run calculation" + "calculator": Find online calculators to assist with sizing and calculating pressure drops for meter runs.

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