The pressure in a pipe depends on static, working outlet pressure, distance and flow rate.

For what you want to know you need to plot a system curve.

Take a flow calculate friction loss per unit length. multiply by length and add the lot.

if this is repeated for different flows the curve can be plotted.

Your answer can be obtained from the system curve.

Is this a problem from a class or the real world?

I think you need to give us more details of your pipe situation.

Do you know the flow at 95psi?

If there is a pump in the system, then you can calculate the head loss in the pipe, the fittings (elbows, tees, etc), the valves, strainers, filters, etc and add any elevation head if it is not closed loop. THEN plot the calculated pressure on the pump curve and whereever they intersect you should be able to read the flow rate.

To get the flow at a different pressure (I'm assuming this is hea loss), realize that the pressure loss is proportional to velocity squared. Double the velocity in the pipe and the head will increase by a factor of four. Halve the velocity and the new head loss will be one fourth of the original.

Check out the Cameron Hydraulic Data book. It has the loss for all the pipe fittings. Lots of fluid mechanics books will have that data also.

There's a whole bunch of factors you gotta take into consideration: pipe type, roughness, rust, water slime, Reynolds number, velocity, etc. If I had much to do, I'd join efunda for a month ($6) and use their nifty calculator. If I was broke as I usually am, I'd get out my trusty old pipe charts (in my beatup 3rd edition of Mark's Handbook) and look it up there.

You can try the following link.

http://www.spiraxsarco.com/us/resources/calculators/pipes.asp

Yes Dweezle,

It is very interesting site which includes a lot of Calculators with a great help for whom interested in fluid mechanics of water mixing and steam.

95 lbs through what size pipe? valves open or closed?

come on now the flow could be anyn thing - zero or a million gallons a minute!

Pressure and flow are interdependent but many other known factors are required to make a determination of your request.

Firstly what kind of instrument you are using to measure the flow? Let me suggest you this, You can use a Verabar flow meter or any Dp flow meter in which you will take two tappings. From this tappings you will get the Dp which is later calibrated in terms of flow. From the same tappings you can also calculate the Presure in the line using a Pressure Transmitter. So when ever you get the flow in the line you can also read the pressure at that point too. Making it simple, use a Bourdon Tube Pressure Gauge or transmitter immediately before the flow meter (3XD distance before the flowmeter is advisable; where D is the diameter of the pipe)

Knowing the pressure of any liquid inside any pipe is not a sufficient data to calculate the flow rate, since there are a lot of flow rates can be established at the same pressure. But knowing the ΔP inside the pipe by throttling (using orifice flange with orifice plate) can be connected to a flow transmitter FT and flow indicator FI.

So, no way to find the flow rate for certain case with a pressure 95 psi nor 65 psi, unless you have a full system hydraulic data.

I can see a lot of bullshit comments, it's simply:

Q=¼πD² √(2P/ρ)

Q = flowrate

π = 3.14

D = inside diameter

P = pressure difference

ρ = density of fluid

N.B. units to be consistent

What units for Q? Is that in gpm?

hey guys, your are all right: flow calculations can be quite difficult. But I think we should go for a most simple approach first ...

The most simple anwer is: one flow rate (for a certain fluid pressure) must be measured - use a bucket or a drum and fill in the flow for 60 or 120 seconds. Then the flow rate is: Q = Volume/(number of minutes). If you can't do this job you really are faced with all the things asked and mentioned by the other contributors.

Assuming the flow resistances would not change their character (laminar, turbulent) a sufficient approximation about effects on flow due to changing fluid pressures can be made with:

Q2 = Q1 √(p2 / p1) ; with pressures as gauge-pressures

For water this kind of recalculation can be made in case the pressure deviations are moderate, for instance +/-30%. Let's say, such approximation gives a sufficient idea what results can be expected.

If you're looking to calculate the flow with equations on a straight run of pipe, you need to use the Bernoulli equation. For a branched section of pipe, you will need to use an iterative process such as the Hardy-Cross method.

For finding flow without calculations, I've used an ultrasonic flow meter before. You just need to have a pressure gauge to make sure the flow you measure is at the pressure you want.

Without reading more into the question I would suggest the flow charts available at www.elkhartbrass.com. I tried to cut and paste the chart, but I just can't cut it. I hope this helps.

hai i have doubt on flow the medium pressure steam economic velocity 25m/S (8BAR). depend on this i calculte the pipe diameter , if velocity is raised to 30m/s what is the pressue. exact question in 8 bar steam pressure how much velocity head how we calculate.