Pump system design and operating-point analysis
A pump does not run at the duty point on the datasheet. It runs where its curve crosses the resistance of the system it is connected to, and that intersection moves the moment you change a pipe size, a static lift or a valve setting. Fluid Network Studio is browser-based pump system design software that finds the operating point for you, then reads off the efficiency, the shaft power and the cavitation margin at that point, so you can see whether the pump you have chosen actually suits the system you have drawn.
It runs in your browser, with no desktop licence and no install. Pump duty analysis is part of the Basic plan, from A$20/month.
The pump curve meets the system curve
Every centrifugal pump has a head versus flow curve: it produces a lot of head at low flow and less as the flow rises. Every system has a curve too, a static lift plus a friction term that climbs with the square of flow. The pump can only deliver where the two curves meet. That intersection is the operating point, and it is the single most important number in pump selection.
Fluid Network Studio fits a head-flow curve through the points you enter using least squares, builds the system curve from the actual network, and solves for the flow where they cross. The pump and system example shows the whole picture: a centrifugal pump lifts water from a reservoir at 5 m head into one at 30 m through 800 m of 200 mm pipe. The pump curve runs from 50 m at no flow down through 40 m and 20 m at higher flows, and the flow settles where that curve meets the static lift plus friction. Change the pipe diameter or the lift and the operating point moves with it, exactly as it would on site.
Efficiency and the best-efficiency point
Hitting the duty head is necessary but not sufficient. A pump running far from its best-efficiency point wastes energy, runs hot and wears faster, so you want the operating point to sit near the peak of the efficiency curve.
Fluid Network Studio takes an efficiency curve as well as a head curve. In the pump and system example the efficiency runs from 62 per cent up to a peak of 78 per cent and back down to 70 per cent across the flow range. The solver reports the efficiency at the operating point, identifies the best-efficiency point, and runs an operating-region check so you can see whether the duty sits in a sensible band or out on the edge of the curve where the pump should not live. That check is the difference between a pump that runs quietly for years and one that is back on the bench within months.
Shaft power versus hydraulic power
There are two power numbers that matter and they are not the same. The hydraulic power is the useful power added to the fluid, density times gravity times flow times head. The shaft power is what the motor has to deliver, and it is larger because the pump is not perfectly efficient: shaft power is hydraulic power divided by efficiency.
Fluid Network Studio reports both. Reading them at the operating point tells you the motor size you need and the energy the duty will cost to run, which is the figure that drives the lifetime cost of the installation far more than the purchase price of the pump. If the distinction between the two is unfamiliar, the glossary sets it out alongside the other terms the solver uses.
NPSHa and cavitation
A pump that cannot get enough suction pressure will cavitate: vapour bubbles form at the impeller eye and collapse violently, eroding the metal and collapsing the head. The guard against it is making sure the net positive suction head available, NPSHa, stays comfortably above what the pump requires.
Fluid Network Studio computes NPSHa from the suction-side conditions and the fluid's vapour pressure, evaluated with the Antoine equation, and raises a cavitation-risk flag when the margin is thin. Checking this at design time, rather than discovering it as noise and damage on commissioning, is one of the most valuable things a pump calculation can do for you.
Variable-speed pumps
Many pumps no longer run at a fixed speed. A variable-speed drive lets the pump match its output to a changing demand, and the affinity laws describe how the curve shifts: flow scales with speed, head with the square of speed and power with the cube. That cube is why throttling a fixed-speed pump is wasteful and why turning the speed down instead saves so much energy.
Fluid Network Studio applies the affinity laws so you can scale a pump curve to a reduced speed and find the new operating point. That lets you check whether a single variable-speed pump can cover the whole duty range, or size the turn-down you need to hold a pressure as demand falls, all before the drive is specified.
What the solver does and does not claim
Fluid Network Studio computes steady-state flows, heads, pressures, efficiencies and power from the data you enter. It supports your engineering work rather than replacing it. Results should be reviewed by a qualified engineer for the specific application before you rely on them, and Fluid Network Studio does not claim compliance with or certification against any particular standard.
Frequently asked questions
What is a pump operating point?
The operating point is the single flow and head at which a pump actually runs in a given system: the point where the pump's head-flow curve crosses the system curve. Fluid Network Studio solves for it directly and marks it on the pump chart.
How does Fluid Network Studio find the operating point?
You enter the pump's catalogue head-flow points; the tool fits a least-squares curve, builds the system curve from the network you have drawn, and solves for the flow where the two cross. Change a pipe size or the static lift and the operating point moves with it.
Does it calculate pump efficiency, BEP and shaft power?
Yes. Give the pump an efficiency curve and it reports the efficiency at the operating point, identifies the best-efficiency point, and runs an operating-region check. It reports both the hydraulic power and the larger shaft power the motor must deliver.
Can it check NPSH and cavitation risk?
Yes. It computes the net positive suction head available (NPSHa) from the suction-side conditions and the fluid's vapour pressure, evaluated with the Antoine equation, and raises a cavitation-risk flag when the margin is thin.
Does it handle variable-speed pumps?
Yes. It applies the affinity laws (flow with speed, head with speed squared, power with speed cubed) so you can scale a pump curve to a reduced speed and find the new operating point.
How much does pump system design cost?
Pump duty analysis is part of the Basic plan, from A$20 a month or A$200 a year, with a free Explorer tier for building and running the built-in examples.
Find your pump's operating point
The surest way to know where a pump will run is to draw the system and solve it. Open the Studio, lay out your suction and delivery, drop in the pump with its head and efficiency curves, and read the operating point, the efficiency, the power and the NPSHa margin. Start from the pump and system example and swap in your own curve and pipe sizes.
Open the Studio and find your pump's operating point in your browser. Pump system design is part of the Basic plan, A$20/month or A$200/year.