Typical vibration levels with the EnviroPump and Seal VIT-500 and VIT-1000 pumps
are 0.02 in/sec to 0.04 in/sec as compared to ANSI allowable levels of 0.25 in/sec.
Comparison of ANSI Pump Rotating Element Strength:
| ANSI Group 1 | Recommended Maximum |
EnviroPump VIT-500 |
Goulds 3196ST/STX |
Durco Mark III |
Durco Mark II |
| Shaft Diameter Between Bearings. | 2.00″ | 1.50″ | 1.50″ | 1.25″ | |
| Shaft Diameter Under Sleeve | No Sleeve | 1.125″ | 1.125″ | 0.875″ | |
| Shaft Diameter Solid Shaft | 1.625″ | 1.375″ | 1.375″ | 1.375″ | |
| Impeller Stability Factor (L3/D4)(1) Sleeved/Solid | 30 | 30 | 143/64 | 140/62 | 346/126 |
| Seal Stability Factor (T3/D4)(2) Sleeved/Solid | 5 | 4 | 18/8 | 18/8 | 43/16 |
| Bearing Stability Factor (SL2/DB4)(3) Sleeved/Solid | 10 | 8 | 31 | 31 | 57 |
| Pump Stability Factor(4) Sleeved/Solid | 45 | 42 | 192/103 | 189/101 | 446/199 |
| ANSI GROUP 2 | Recommended Maximum |
EnviroPump VIT-1000 |
Goulds 3196MT/MTX |
Durco Mark III |
Durco Mark II |
| Shaft Diameter Between Bearings. | 3.00″ | 2.125″ | 2.20″ | 2.20″ | |
| Shaft Diameter Under Sleeve | No Sleeve | 1.50″ | 1.50″ | 1.50″ | |
| Shaft Diameter Solid Shaft | 2.125″ | 1.75″ | 1.875″ | 1.875″ | |
| Impeller Stability Factor (L3/D4)(1) Sleeved /Solid | 30 | 20 | 112/63 | 90/49 | 90/49 |
| Seal Stability Factor (T3/D4)(2) Sleeved /Solid | 5 | 4 | 15/8 | 13/7 | 13/7 |
| Bearing Stability Factor (SL2/DB4)(3) Sleeved/Solid | 10 | 6 | 23/23 | 12/12 | 12/12 |
| Pump Stability Factor(4) Sleeved/Solid | 45 | 30 | 152/94 | 115/68 | 115/68 |
All values are approximate.
(1) Impeller Stability Factor (ISF) =L3/D4 pumps with single row bearings, and (0.75)L3/D4 for pumps with tandem bearing forward.
(2) Seal Stability factor (SSF). Function of the distance from the nearest bearing to mid way between double seal (T), and diameter of the shaft (not the shaft sleeve) at the seal.
For single row bearing SSF=T3/D4. For tandem bearing forward SSF=(0.7)T3/D4.
(3) Bearing Stability Factor (BSF)=SL2/DB4.
(4) Pump Stability Factor (PSF)=(.75 if tandem) L3/D4 + (.75 if tandem) T3/D4 + SL2/DB4.
Benefits:
- Impeller Stability Factor (ISF)-one of the lowest in the world, resulting in greatly reduced deflection and vibration.
- Seal Stability Factor (SSF)-one of the lowest in the world (which can be reduced further to 0.4 with rear seal locations), resulting is stable, flat seal face operation, and lowest leakage.
- Bearing Stability Factor (BSF) measures shaft resistance to “bow” effect between bearings as load is applied at the end of shaft.
- Pump Stability Factor (PSF) is the combined value of all three factors. The lower the number, the better performance under “off peak” conditions, upsets, lowest vibration, lowest cavitation effects, and best seal stability.