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How to select a suitable thermowell

Differential pressure (DP) flow measurement is a crucial process in various industries, from oil and gas to carbon capture storage and water treatment etc.. Two common devices used for DP flow measurement are orifice plates and averaging Pitot tubes. Both have their advantages and are suited for different applications. In this article, we will explore the advantages of each and compare them to help you make an informed decision.

Advantages of Orifice Plates

1) Simplicity and Reliability

Orifice plates are known for their simplicity. They consist of a plate with a precisely drilled hole to create the differential pressure. This simplicity makes them reliable and easy to maintain and replace. They have no moving parts, removing the risk of mechanical failure.

2) Cost-effective

Orifice plates are cost-effective compared to many other flow measurement devices. The initial investment is relatively low, making them a favorable option for projects with budget constraints.

3) Wide Range of Applications

Orifice plates can be used in a wide range of applications, from clean liquids to gases with solids. They are versatile and suitable for both low and high-pressure systems.

4) Well-Documented Standards

Orifice plate design and installation follow well-documented industry standards, ensuring accuracy and repeatability in measurements.

Advantages of Averaging Pitot Tubes

1) Multiple Bores

They provide a precise measurement of flow velocity by averaging the pressures at multiple points within a pipe, reducing the impact of turbulence.

2) Low Permanent Pressure Loss

Averaging Pitot tubes have lower permanent pressure loss compared to orifice plates. This means they are not as affected by the pressure and flow rate, making them efficient for long-term operation.

3) Easy Installation

Averaging Pitot tubes can be installed in existing pipe works without adding flanges. This significantly lowers the total cost a flow meter installation.

4) Minimal Maintenance

These devices have no moving parts, reducing the need for frequent maintenance. Their robust design allows them to withstand harsh conditions. A purge unit can be added if the process consists of solids that can cause blockage.

Comparison of Orifice Plates and Averaging Pitot Tubes


If the focus is high accuracy, then the orifice plate should be the preferred choice. The averaging Pitot tube requires a quite long straight pipe run to be able to deliver the same high accuracy. However, the repeatability of the Pitot tube is quite high, so the accuracy is reliable and constant.


Orifice plates as a standalone product are generally more cost-effective than averaging Pitot tubes, however looking at the full installation the orifice plate requires orifice flanges meaning the total cost of a flow measurement can surpass the cost of the Pitot Tube

Pressure Loss

Averaging Pitot tubes have a much lower permanent pressure loss.


Both Orifice plates and Pitot tubes are versatile and suitable for a wide range of applications. When pipe sizes become larger than 500-750 mm, Pitot tubes scalability takes the advantage.


Both devices are low-maintenance due to their lack of moving parts. The installation of the Pitot tube makes it extremely easy to replace.


In summary, orifice plates and averaging Pitot tubes are both valuable tools for differential pressure flow measurement, each with its own set of advantages. Orifice plates are cost-effective, reliable, and versatile, making them a solid choice for many applications. On the other hand, averaging Pitot tubes offer lower installation cost, lower pressure loss, and is better great for larger pipe sizes

The choice between these two devices ultimately depends on your specific application, budget, and accuracy requirements. Consider the nature of your fluid, the level of accuracy needed, and the long-term operating costs to make an informed decision. Regardless of your choice, proper installation and maintenance are essential to ensure accurate and reliable flow measurements.