Pipe system
Awaiting Valid Duty Parameters
Adjust the parameters on the left to compute live hydraulic values, ranges, and sizing verdicts.
Need the suction layout checked?
Undersized suction piping causes most cavitation and priming complaints. Our engineers verify suction sizing and NPSH on chemical pumps across Gujarat.
How to size pump piping
Why velocity bands matter
Pump piping is sized by velocity, not just by fitting the flange. On the suction side, high velocity raises friction and drops NPSH available, inviting cavitation — so the band is deliberately conservative at 0.6–1.5 m/s. On the discharge side, velocity above about 3 m/s increases friction loss, erosion and water hammer in chemical service. The calculator returns the smallest standard DN inside the band: the cheapest pipe that still behaves.
The classic engineering rule is to size the suction line one size larger than the pump inlet. The velocity method used here is more precise and is the one Teflow's engineers apply when a pump keeps losing suction or cavitating.
Reading the results
For each flow the calculator lists candidate DN sizes with their velocities and flags the recommended size. A 25 m³/h discharge picks DN80 at about 1.46 m/s (Schedule 40); the same flow on suction prefers the same DN80 just inside the 0.6–1.5 m/s band, or DN100 if you want more margin. Friction loss per 100 m is computed with the Darcy–Weisbach equation so you can build the system curve.
Schedule 80 is recommended for corrosive chemical service above about 10 bar or where extra wall thickness is needed for erosion — the schedule choice changes the inner diameter and therefore the velocity, so re-run the calculation when you switch schedules.
Chemical service notes
PTFE-lined and PP pipe have different inner diameters and pressure ratings than steel, and fittings add equivalent-length losses. For lined systems, use the liner supplier's bore and the same velocity bands. Suction runs should be as short and straight as practical, with the strainer sized for low pressure drop — a clogged suction strainer is the most common cause of a pump that was correctly sized but still cavitates.
For a complete suction analysis, combine this calculator with the NPSH available calculator and the head-loss tool: friction from the pipe, fittings and strainer all subtract from NPSHa.
When to upsize
Upsize the suction line when the liquid is hot (vapor pressure high), viscous, or the pump runs at 2900 rpm with a long suction run. A general rule: keep suction friction below 0.5 m for low-NPSHr pumps and below 1 m otherwise. Teflow's engineers confirm the suction system against the pump's NPSHr curve on every installation and repair visit — call +91 98251 62709 for a check.
Technical & Operational FAQs
Q1.What velocity should pump suction pipe use?
Keep suction velocity between 0.6 and 1.5 m/s. Above 1.5 m/s friction rises and NPSH available drops, which invites cavitation on most chemical pumps. Below 0.6 m/s the pipe is oversized and costly. Discharge lines run 1.5–3 m/s. The calculator applies these bands automatically.
Q2.Is the discharge pipe size the same as the pump flange?
Not always. The pump flange is fixed by the manufacturer, but the piping can be one size larger, especially on the suction side. Common practice: suction line one size larger than the suction flange, discharge line equal to or one size larger than the discharge flange. Velocity, not flange size, decides the final pipe.
Q3.What is the friction loss per 100 m?
Friction loss is the head consumed by the pipe over a given length, computed here with the Darcy–Weisbach equation for water-like liquids. It feeds directly into the total dynamic head and NPSH calculations. For a 25 m³/h flow in DN80 Schedule 40, friction is roughly 0.9–1.2 m per 100 m depending on roughness.
Q4.Schedule 40 or Schedule 80 for chemicals?
Schedule 80 has a thicker wall, so it handles higher pressure and gives more erosion allowance for slurries and corrosive service — but the smaller bore raises velocity. For clean chemical duty up to about 10 bar, Schedule 40 is standard; above that, or for abrasive duty, use Schedule 80 and re-check the velocity.
Q5.How do I check suction pipe for NPSH?
Add the suction friction loss (pipe, fittings, strainer, valves) and subtract it from the static suction head in the NPSH available calculation, along with the liquid vapor pressure at pumping temperature. If the result is below the pump's NPSHr plus 0.5 m margin, enlarge the suction pipe or raise the tank.
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Need a custom hydraulic audit or specific duty curve verification? Call +91 98251 62709 or Request a Detailed Engineering Quote.