Top 5 Most Popular  1. Pressure drop 2. Reynolds Number 3. Pressure drop K coefficients 4. Churchill equation 5. Moody diagram

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The fluid velocity in a pipe is a fundamental data to calculate to be able to characterize the flow in a pipe, thanks to the Reynolds number, and size a pipe circuit calculating the pressure drop expected for a certain flow.

1Double Check Backflow Preventer

Warning : this calculator is provided to illustrate the concepts mentioned in this webpage, it is not intended for detail design. It is not a commercial product, no guarantee is given on the results. Please consult a reputable designer for all detail design you may need.

These values are given as an indication for pre-sizing. Each company should have its own guideline to be followed.

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When designing the pipe, it is necessary to chose a fluid velocity to have good compromise in between pressure drop and economics, some recommendations are given below.

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In addition to the sources given below, one may also wish to consult Applied Process Design for Chemicals and Petrochemicals plants, Ludwig, Gulf, page 85 which is giving values for specific applications like sodium hydroxide, ethylene, vinyl chloride...

Double Check ValveAssembly

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The Double Check Valve Backflow Preventer shall be Australian Watermark Certified (AZ/NZS 2845.1), rated to 82°C and supplied with male pipe thread tailpieces. The main body shall be Bronze. The housing shall be reinforced Nylon and the seat disc elastomers shall be silicone. The first and second checks shall be accessible for maintenance without removing the device from the line. The Double Check Valve Backflow Preventer shall be a ZURN WILKINS Model 350.

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The Zurn Wilkins 350 Series Backflow Preventer is a Medium Hazard, High-Performance Low Head Loss Backflow Preventer that features a lightweight ductile iron body, offering durability and easy installation. Constructed with corrosion-resistant low-lead materials, as well as all-plastic and stainless-steel components, this backflow preventer guarantees long-lasting reliability, ensuring a secure and efficient water system.

1/2Double Check Backflow Preventer

Note that the velocity will be constant for a non compressible fluid but will vary with a compressible fluid such as a gas. For a gas it is therefore necessary to slice the pipe layout in several sections in order to recalculate the velocity along the pipe.

You can access to an Excel calculation tool in order to calculate the velocity a fluid in a pipe, knowing the pipe diameter and the fluid flowrate  : Fluid velocity in pipe Excel calculation tool (click here)

Local codes shall govern installation requirements. To be installed in accordance with the manufacturers’ instructions and the latest edition of the Plumbing Code of Australia and/or AS/NZS 3500.

2Double Check Valve Backflow Preventer

With : Q = Volumetric flowrate (m3/s) D = Pipe diameter (m) u = Fluid velocity in pipe (m/s)

Designed for installation on water lines to protect against both back siphonage and backpressure of polluted water into the water supply. Double Check Valve Assembly shall provide protection where a potential health hazard exists. (Medium Hazard)