Flow nozzles are for providing differential pressure flow measurement, but they can also be used to provide a general restriction or pressure drop. We offer three types of flow nozzles: the basic flow nozzle, the venturi nozzle, and the venturi tube. We also offer three installation styles; flanged, welded, or insertable. Not every installation type is practical to use with every nozzle type in every size, as often it will depend on the specific application.
The Venturi Tube
The CPA Venturi Tube flow nozzle is a differential pressure measurement device consisting of a cylindrical upstream inlet section, a converging inlet cone, a cylindrical throat, and an expanding outlet cone. The upstream and downstream pressure taps are included in the Venturi Tube design.
All CPA Venturi Tubes are custom designed for your specific application or process conditions. Many aspects of the Venturi Tube design are customizable, including the overall length, process connections, number of pressure taps, beta ratio, and more. For simplicity, CPA machines each of our venturi tubes out of a single piece of material. This ensures higher strength and structural integrity as no welding is required. This also reduces the amount of non destructive testing that would be needed. Like all CPA products, the Venturi Tube can be manufactured from many different material components, and are available in a large range of sizes and materials.
The first step when custom designing a Venturi Tube is to determine both the application and the installation conditions. To do so, we need to know:
- Installation Type
- Nominal Pipe Size and Pipe Schedule
- Material Requirements
- Maximum Design Temperature and Pressure
- Minimum Design Temperature
The next step is to determine the nozzle’s beta ratio. To calculate this, we need to know:
- Maximum Flow Rate
- Fluid Composition
- Differential Pressure Requirements
- Flowing Pressure and Temperature
This information is combined using equations from the flow standard ASME MFC 3M, and the output is the nozzle beta ratio. A flow nozzle can only be sized around a single combination of the above flow conditions. This combination sets the nozzle behaviour at every other flow rate and pressure/temperature. The nozzle’s beta ratio also determines many of the nozzle’s other physical dimensions, including inlet length, exit length, and minimum overall size.
The last step requires the finishing details, and information about any special documentation or testing conditions (if applicable), including:
- Tap Connections (Number of NPT or Socket Weld Connections, and Position)
- Length/Diameter Restrictions
- CRN Requirements
- Hydrotest Requirements
- Other Non-Destructive Tests (ex. PMI, Impact Test)
- Required Labelling/Marking
Once this information is obtained and finalized, the Venturi Tube is ready to be drawn up and sent for manufacturing. It is important to note that our Venturi Tubes are manufactured to recognized industry standards, such as ASME, ANSI, and ISO.
Contact Us
At CPA, we have the expertise to custom manufacture Venturi Tubes to suit your unique process conditions and size requirements. We deliver a finished product with no moving parts, no maintenance requirements, and a guaranteed low fouling rate with excellent reliability. Contact us today at 403-236-4480 to discuss how we can help you achieve accurate flow measurement.
