Flow Orifices in Pipes

Sample points takeoffs at intervals are not such highly designed flow orifice reuirements as extensive engineering undertaken for orifice plates for flow metering of steam/gas/air/water or orifice steam traps. They used an orifice plate possibly a 1/8" on a 20mm line size.They could've used a needle valve or a small water pressure reducing valve instead just to ensure a steady flow for sampling. You can never size an orifice unless you yourself do not provide the data of pressure, temperature, flow, pressure drop etc., this is something you yourself may not know. Thus in your case they used this orifice to ensure steady flow and safeguard against splashes by simply holding back the pressure behind the orifice.

can any one give the formula seperately for the compressible and non compressible fluids,

to find the characteristics like change in flow,change in pressure,change in velocity.

me too looking for the same thing but for air

can any one help in this regards

Nandakumar

There is much available information on using an orifice to control or meter flow. You don't mention the pressure or temperature of the water, but listed below are some links you should find helpful. It is always wise to verify any calculated results empirically.

Gas calculator:

http://www.lenoxlaser.com/calculator/orifice.asp

Liquid tutorial (general):

http://www.omega.com/techref/flowcontrol.html

Liquid calculator:

http://www.pipeflowcalculations.com/orifice/index.htm

This sounds like a common Cicil problem

there are many programs to do this

ACad even has modules that can help

You said that this is a "sanitary water loop" for a pharmaceutical application.

If so, the most important design criteria to take into account should be keeping "sanitary" the distribution loop and also being able to be validated after performing any change, according to the GMPs regulations.

Orifice plates are inappropiate as a method of flow control except when absolutely necessary and only when they can be designed with minimal potential dead legs.

For point-of-use flow rate control, proper valve sizing is more appropiate. It is absolutely important that every valve in the loop should be a "zero dead leg" valve as this avoids stagnant water keeping all the water within the loop recirculating as required by the regulations, allowing for a complete drain of the loop when needed.

Please check with the people specialized in sanitary water loops, sanitary valves suppliers and the validation team, and get from them the best recommendations to solve your flow control problems.

I strongly suggest that you read books and articles devoted to sanitary water loops design, to learn about the principles and technologies involved in this application.

By the way, I have read some suggestions on needle valves and this sort of devices. Well, they are not sanitary and should not be used at all. Look only for approved "zero dead leg" valves. For every part you use for such a loop, get a design certificate as being sanitary and also a materials certificate. For instance, 316L stainless steel means nothing from a validation point of view, unless you have a materials certificate proving it and also that it has a composition compatible with its intended sanitary use.

Please read "Pharmaceutical Water - System Design, Operation and Validation" by William V. Collentro, Interpharm Press, Inc., Buffalo Grove, Illinois. You will find this book quite useful.

Do not attempt to modify a pharma water system without a careful planning and a validation plan. Doing anything without taking the proper measures can lead to a disaster and also to face big troubles with the regulatory authorities.

I hope that you'll find my comments useful.

Why don't you use a small needle valve, or even a small diameter solenoid valve to take the samples? This way you'd avoid stagnation points behind and forward of the orifice that could hold deposits from the water, and you'd eliminate one piece (the orifice). IT's much more logic.

Regards.

-----

To dream the impossible dream, to fight the unbeatable foe, to bear with unbearable sorrow, to run where the brave dare not go...
To right the unrightable wrong, to love pure and chaste from afar, to try when your arms are too weary to reach the unreachable star!

Zero-dead leg diaphragm valves or needle valves would be more appropriate solutions. Orifice plates are almost unknown in pharmaceutical water applications.