# What is the purified water velocity limit and where it is mentioned

what is the purified water velocity limit and where it was mentioned

@jamalbasha Velocity of purified water in circulation loop should not be less than 1.5 m/s to avoid the biofilm formation.

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Dear sir,

Which guideline it is mentioned.

Velocity increase in loop what is the problem

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What is the Reynolds number for pharmaceutical water system distribution lopp

How to calculate the Reynolds number

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Sor can u please mention the refrence ???

More than 4000 Reynolds

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In purified water distribution loop a turbulent flow regime must be maintained at the point of return of the loop in order to avoid the biofilm formation. The velocity depends on the pipe’s diameter, that’s why you can reach a fully developed turbulent flow regime (Reynolds higher than 4000) with velocity values ​​below 1.5 m/s.
Greets, Tania

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To control return loop conductivity velocity of water need to maintain.

The Reynolds number measures the turbulence of water
flowing in the distribution pipelines. If the Reynolds number
is above 2000, the water has turbulent flow. If the
Reynolds number is below 2000, the water may have laminar
flow, which may lead to biofilm development

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With velocity of purified water in circulation loop should not be less than 1.5 m/s. If there are about 30% of the user points open the valve to get water is difficult to achieve. Kindly advise!

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PLEASE NARROW YOUR IN-HOUSE LIMIT TO 3.0 M/S (OR VALIDATE) YOU WILL GET AT LEAST 1.5 M/S ALL THE TIME DURING OPENING OF 30% OF VALVE AT USER POINT.

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Actually if the Reynolds number is between 2000 to 4000, the water flow regime will not fully developed turbulent and it’s called transition regime between laminar and turbulent flow.
So I believe that we should consider the Reynolds number more than 4000 to avoiding biofilm development besides high value velocity limitation which could lead to high pressure drop in our distribution system.

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Dear Ankur Sir,
1.5 m/s in supply or in return?

Valve opening percentage is not the right concept to define increases/decreases in velocity because discharge size of valve may differ. for that we have to check the user point discharge flow and same to be compared with designed peak load, if it is meeting the peak load criteria then we can challenge the velocity.

Dear, there may two reasons (mainly) either your VFD is not controlling the pump speed or PID values got changed. also check whether the flow meter is calibrated properly.

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