Pumps and Pipe Rating

The volume and outlet pressure are determined by the need.

The maximum flow rate may be manipulated by spreading the total demand over longer periods by providing storage.

With the flow rate and the locations known the system can be designed.

The pump must be capable of delivering the water at a pressure to overcome static + friction + required pressure.

The choice of pipe size will be determined by the required flow rate - The additional capital cost of a bigger pipe may be canceled out by lower running costs. A sweet spot must be calculated.

Fittings will have an effect and they are usually represented as a length of pipe.

With the duty point at hand the best pump can be selected. It is always better to select the highest affordable efficiency available.

The local suppliers may be the best to contact. They usually have the ability to assist.

Feel free to ask for further advice.

Very good summary of what is a large amount of work. If you know nothing about the subject then it is quite a risk to try and do it all yourself. The potential cost if you get it wrong can be very high and it is maybe better to get someone who knows to show you how.

I'm actually mainly self taught on this subject but I spent many many hours going through books, then getting muddled up with calculations and getting several different answers to the same question before it clicked. If there was someone to show me how they do it then I would have saved alot of time.

Each system is unique therefore giving it's own problems and this is something which takes time to learn. Another thing I found was that when I did all the calculations and submitted a report to the managment they would usually turn round and say it was rubbish, we can do it with much smaller pipes and smaller pumps etc, to save money. You have to be very sure about your results and stand your ground or else things can go very wrong.

The proceture as shown below

1- Calculate the total flow rate according to number of fixture , type of application or numder of population ( See www.PDH on line.org )

2- Sellect recomended velosity according to your application there are tables for this purpose .

3- Inter charts ( as pipe material ) you have flow rate ( item 1 ) & velosity ( item 2 )

you can find pipe diameter & friction loss per length of pipe .

4- From tables calculate equivalent length for fittings , accessories & valves

5- Messure total lenth of the pipe + equivalent length for fittings ( item 4 ) =total equivalent length of network.

6-Find total pressure drop = friction loss per length * total equivalent length

7 - Pump head = ( total pressure drop + static head )*1.1 ( safty factor ).

8- From characrisic curve of pump manufacturer & pump type you need can be sellecte the pump for maximum effeciency .

is there any manuals or online books that i can refer..i want to study about pumps and fittings.

i am in electrical engineer working in a company which doing water treatment and all in UAE.iam interested in mechanical part also if even if i am doing the electrical part only

You have already been supplied with all the technical details.....but what is the application?

I am a pump consultant and can help you wih your actual application; there is no quick two line answer to your question. The liability to wrong pump selection or application can be very high; if you have a real application contact email me at lchauhan@flpumps.com

I agree with the guest. If a too large pump is selected then you can have cavatation. Or more simply you suck up all of the water too quick and the pump will cut on and off too much and wear itself out too quickly. Also without a check valve there are cases where the water in the pipe can flow back into the the pump well and make the pump kick on and off and on and off ... etc.

Remember the Bernoulli's Continuity Equation (Energy Conservation), then remember the pressure differential between two points in the pipe. It's a factor of the fluid velocity, hydraulic or equivalent lengths, surface roughness and pipe diameter.

dP = ƒV²/2(L/D), where ƒ= 1/Re^-½ and Re = ρDV/μ, Re is Reynolds No, ρ, the fluid density, D, the pipe wetted area, μ, dynamic viscosity of the fluid, V the velocity of the fluid in the pipe and L the total hydraulic length. the fittings such as elbows, nipples unions, valves on the lines are calculated in equivalent length and there are book values for them.In essence, you must maintain consistency in your units. The total pressure differential is the sum of hydrostatic pressures, pressure drops along the line of flow (friction) and over the fixtures. The value is in metres and it's called pressure head, H. Adding about 10-20% to this value will take care of ommited energy drop (pressure drop). Armed with this value, The Pump capacity could be computed using the Power Equation below:

P = 8.134QHρs/η where P is pump power in kW, Q is volumetric flow rate m³s^-1, H is pressure head in metre, s - specific gravity of the fluid and η - efficiency of the pump and for centrifugal η ≤ 0.65. The pump characteristic chart could be used to choose the most appropriate unit (pump). almost dropped is the density ρ in kgm^-3.

hrecules53, Ibadan, South West, Nigeria

Three important rules to be taken into consideration:

Rule 1. It is a rule of thumb and according to codes and standards, after design and selection of pump inlet and outlet nozzles (by manufacturer) to select the NPS of both suction side and delivery side piping to be larger than the NPS of pump nozzles, so you have to use a reducers to minimize friction loss and pressure drop.

Rule 2. The reducer at inlet side must be eccentric (not concentric) and top flat to avoid accumulation of gases, air and vapor at inlet side, and allow its routine escaping.

Rule 3. We know that the velocity of fluid along pipe section is parabolic, with its max. value at middle and zero velocity adjacent to pipe wall, therefore when you use a conical strainer at the suction side, the strainer must be erected with its head towards the reverse direction of flow, to allow gathering of any impurities along and adhered to the internal wall of pipe where the adjacent velocity reaches zero. Because if you erect the conical strainer with its head towards flow direction, the impurities shall be collected at the middle of pipe where the max. velocity of fluid which maximize resistance of flow.

Rule2:

Have the code and standards recommends to be eccentric reducer and top flat on the suction installation?

Rule3:

Common strainer are Y-Type either bspt/npt/flanged.

In liquid i used concentric and bottom flat reducers at the pump suction. no cavitation at all. Roll of thumb in practical start-up is that bleed the pump out of air/gas/vapor before starting. observe fluctuation of pressure guages to make sure air/gas/vapor are all escape. we are talking of contineous pumping of liquid.

jojie_oak

Is rule no.3 applicable to compressors also?

Yes