Three numbers
Suction, discharge and nominal impeller diameter in millimetres, as KSB writes Etanorm sizes: 040-025-160 is a DN 40 suction, a DN 25 discharge and a 160 mm nominal impeller.
Reference tool — not a selection
Read a pump size before it goes in an RFQ.
End-suction pump
Nozzles, impeller, range.
Type the designation as on the plate. Below the examples, an offered pump can be checked against it: the nozzles, the impeller and the range. The drawing, the rows and the RFQ line update with every change.
Examples:
Replacement check
On the designations alone: the curve decides the duty, the plate and the maker’s drawing the parts.
All 130 engineering tools
End-suction centrifugal pumps for cooling water, ballast and fire service carry a size in their designation: 65-50-160, NK 50-250/241, Etanorm 040-025-160. The numbers give the suction and discharge nozzles and the nominal impeller diameter; the number after a slash on a Grundfos plate is the actual impeller diameter. Type the designation, and the reader splits it, shows the nozzles, checks an offered pump and writes the RFQ line.
The nominal duty point that EN 733 and ISO 2858 attach to each size is not given here: the head and flow of the pump in hand come from its curve.
How a size is read
Three numbers or two.
Two numbers
Discharge and nominal impeller only, as on Grundfos NK and NB or Calpeda N plates: NK 50-250 has a DN 50 discharge and a 250 mm impeller, and the suction is one size larger, DN 65.
After the size
A number after a slash on a Grundfos plate is the actual impeller diameter in mm, below or above the nominal one (NK 50-250/241, NK 40-125/130). A letter or a .1 after the size is the maker’s variant.
| Discharge | Suction |
|---|---|
| DN 32 | DN 50 |
| DN 40 | DN 65 |
| DN 50 | DN 65 |
| DN 65 | DN 80 |
| DN 80 | DN 100 |
| DN 100 | DN 125 |
| DN 125 | DN 150 |
| DN 150 | DN 200 |
Pairs from Grundfos NK and NB data and Calpeda’s N table; DN 150 and DN 200 from Grundfos NK 150-315 and KSB’s Etanorm 200-150 sizes. Where a designation gives the suction, what it says holds.
Sources
EN 733 and ISO 2858: the standards’ titles in the ISO, BSI and AFNOR catalogues. Three-number sizes: KSB Etanorm data sheets (040-025-160) and the Etanorm size list (200-150-315, 200-150-400). Two-number sizes and nozzle pairs: Grundfos NK and NB data (Lenntech listings, Grundfos Product Center print-outs) and Calpeda’s N / N4 data sheet. The actual impeller diameter after a slash: the same Grundfos data (NK 40-125/130, NK 50-125/121, NK 50-250/241).
Before you send the request
Questions about pump sizes in an RFQ
What does 65-50-160 mean on a pump?
Three numbers: a DN 65 suction, a DN 50 discharge and a 160 mm nominal impeller. Makers that write two numbers leave the suction out, so 50-160 is the same size.
What is the number after the slash, as in NK 50-250/241?
On Grundfos plates it is the actual impeller diameter in mm: 241 mm in a 250 size. It can also be above the nominal size, as in NK 40-125/130.
Do two pumps of the same size take the same parts?
The size fixes the nozzles and the nominal impeller, and EN 733 (10 bar) and ISO 2858 (16 bar) set the main dimensions for their sizes. The impeller trim, the seal and the wear parts are the maker’s own, so the plate decides.
What should the request include?
The type designation and the serial number from the plate, the motor’s output and speed, the liquid and its temperature, and the part needed; photographs of the plate and the pump in place.
Size read?
Send the line with the pump plate.
A decoded size is a cross-check, not a pump selection. Attach photographs of the plate and the pump in place, and Vessel Core checks them before an offer goes back.
Buyer tools
