Читать книгу Petroleum Refining Design and Applications Handbook - A. Kayode Coker - Страница 34

1 1. Power for pumping liquids: kW = (1.67) [Flow (m3/min)] [∆P(bar)]/ε[hp = Flow (gpm) ∆P (psi)/(1, 714)(ε)]. (ε = fractional efficiency).

2 2. Net positive suction head (NPSH) of a pump must be in excess of a certain number, depending upon the kind of pumps and the conditions, if damage is to be avoided. NPSH = (pressure at the eye of the impeller-vapor pressure)/(ρg). Common range is 1.2–6.1 m (4–20 ft) of liquid.

3 3. Specific speed Ns = (rpm)(gpm)0.5/(head in ft)0.75. Pump may be damaged if certain limits of Ns are exceeded, and efficiency is best in some ranges.

4 4. Centrifugal pumps: Single stage for 0.057–18.9 m3/min (15–5000 gpm), 152 m (500 ft) maximum head; multistage for 0.076–41.6 m3/min (20–11,000 gpm), 1675 m (5500 ft) maximum head. Efficiency: 45% at 0.378 m3/min (100 gpm), 70% at 1.89 m3/min (500 gpm), and 80% at 37.8 m3/min (10,000 gpm).

5 5. Axial pumps for 0.076–378 m3/min (20–100,000 gpm), 12 m (40 ft) head, 65–85% efficiency.

6 6. Rotary pumps for 0.00378–18.9 m3/min (1–5000 gpm), 15,200 m (50,000 ft) head, 50–80% efficiency.

7 7. Reciprocating pumps for 0.0378–37.8 m3/min (10–10,000 gpm), 300 km (1,000,000 ft) maximum head. Efficiency: 70% at 7.46 kW (10 hp), 85% at 37.3 kW (50 hp), and 90% at 373 kW (500 hp).