The Grundfos BM 3A-33N (product number 10731933) is a horizontal, sleeve-enclosed high-pressure booster module from the BM 3A range, built with 33 stages in the N variant — stainless steel sleeve and shaft. The pump element runs inside a pressure sleeve, so system pressure is contained by the sleeve rather than the pump housing — which is what lets a compact module work at reverse-osmosis pressures.
| Stages | 33 |
| Rated head | 475.7 ft |
| Maximum operating pressure | 1199.46 psi |
| Maximum liquid temperature | 104 °F |
| Pipe connection | S |
| Voltage | V |
| Impeller | Stainless steel |
| Gross weight | 180 lb |
| Shipping volume | 4.45 ft³ |
Specifications published by Grundfos for this exact product number.
Official Grundfos curve for this product number — 60 Hz, water at 68 °F.
Dimensional drawing for the BM 3A frame. Confirm critical dimensions against the certified drawing for your order.
| Grundfos product number | 10731933 |
| Model | BM 3A-33N |
| Range | BM 3A |
| Sleeve diameter | BM 4" |
| Build variant | N — stainless steel sleeve and shaft |
Seawater and brackish-water reverse osmosis • membrane feed and interstage boosting • energy-recovery circuits • industrial process water at elevated pressure.
Product photograph shows the BM 4" range; individual configurations differ in length and motor size.
