The Differential Pressure Flow Measuring Principle (Orifice-Nozzle-Venturi)

Summary

The video script explains the critical role of differential pressure flowmeters in industrial piping systems for measuring diverse substances like chemicals, oil, gas, and steam. It highlights the historical contributions of Daniel Bernoulli and Giovanni Battista Venturi to the development of flow measurement. The script details how these meters work, using an orifice plate to create a pressure drop proportional to flow velocity, and discusses various designs like nozzles and Venturi tubes to optimize performance. Endress+Hauser is presented as a supplier of custom-configured flowmeters for a wide range of applications.

Takeaways

• 🌐 Piping systems transport a wide variety of substances, including solvents, chemicals, oil, gas, and steam, each with distinct properties requiring specific measurement methods.
• 📊 Flow measurement based on the differential pressure principle is a key technique for measuring the flow of fluids in pipes.
• 📚 Daniel Bernoulli discovered the relationship between fluid pressure and speed in pipes, while Giovanni Battista Venturi built the first flowmeter, known as the 'Venturi tube'.
• 🔍 Differential pressure flowmeters use an orifice plate with an integrated artificial restriction in the measuring tube to measure flow.
• 🔧 The principle of operation involves measuring the pressure difference created by the fluid's velocity increase as it passes through the orifice plate.
• ⚖️ The differential pressure is directly proportional to the flow velocity, and thus can be used to determine mass and volume flow rates in the pipe.
• 🏭 The orifice plate is widely used in industrial flow measurement, but other designs like nozzles and Venturi tubes are available for specific applications.
• 💨 Nozzles with a rounded inlet reduce turbulence and pressure loss, making them suitable for higher flow velocities and abrasive fluids.
• 🌀 Venturi nozzles and tubes further reduce turbulence by using longer conical constrictions, optimizing for different process conditions.
• 🌍 Industrial flow measurement using differential pressure has been a proven technology for over a century, applicable to various liquids, gases, and steam even under extreme conditions.
• 🏢 Endress+Hauser offers custom-configured, premounted differential pressure flowmeters, providing tailored solutions for all measurement needs.

Q & A

What are the various substances transported in piping systems?

Piping systems transport diverse substances including solvents, chemicals, oil, gas, and steam for energy transmission.

Why are different principles required for measuring different fluids in pipes?

Different fluids flowing through pipes have completely different properties, necessitating various measurement principles to accurately measure their flow.

What is the differential pressure principle in flow measurement?

The differential pressure principle is a method of flow measurement based on the relationship between the pressure drop and flow velocity of a fluid in a pipe.

Who discovered the relationship between pressure and speed of a fluid in a pipe?

Swiss mathematician and physicist Daniel Bernoulli discovered the direct relationship between the pressure and speed of a fluid flowing in a pipe.

What is a Venturi tube and who invented it?

A Venturi tube is a device for measuring fluid flow rate, invented by Italian physicist Giovanni Battista Venturi in 1797.

How does a differential pressure flowmeter with an orifice plate work?

A differential pressure flowmeter with an orifice plate works by measuring the pressure difference before and after the plate, which increases as the fluid velocity increases due to the restriction in the cross-section.

What is the significance of the two holes located before and after the orifice plate?

The two holes located before and after the orifice plate in a pipe are connected to a differential pressure sensor to measure the pressure difference caused by fluid flow.

Why does the static pressure decrease at the orifice plate when fluid starts to flow?

The static pressure decreases at the orifice plate due to the laws of fluid mechanics, as the fluid velocity increases significantly around the plate because of the restriction in the cross-section.

How is the differential pressure measured in a flowmeter related to flow velocity and volume flow?

The differential pressure measured in a flowmeter is directly proportional to the flow velocity and thus to the mass and volume flow in the pipe.

What are some alternatives to the orifice plate for flow measurement?

Alternatives to the orifice plate for flow measurement include nozzles with a rounded funnel-like inlet and Venturi nozzles, which reduce turbulence and pressure loss.

Why are nozzles and Venturi tubes preferred for certain measuring tasks?

Nozzles and Venturi tubes are preferred for certain measuring tasks because they minimize undesired effects such as excessive pressure loss or abrasion of components due to solids carried in the fluid.

How long has industrial flow measurement using differential pressure been in use worldwide?

Industrial flow measurement using differential pressure has been tried and tested in numerous applications worldwide for about 100 years.

What does Endress+Hauser offer in terms of differential pressure flowmeters?

Endress+Hauser offers differential pressure flowmeters that are configured to customer specifications and premounted, providing the right solution for all applications.