In this article will see the Comparison of API 610 VS4 and VS5 Pumps. This comparison is made very crisp and short.
Both VS4 and VS5 type vertical pumps are widely used for loading/unloading and utility services. If you have a doubt in selecting either VS4 pump or VS5 pumps for a particular application, then this article will help you made a conclusion.
What is VS4 pump type?
Vertically suspended pump with single volute casing and the line shaft driven sump pumps shall be designated as VS4 type pumps
What is VS5 pump type?
Vertically suspended pump with single volute casing and the shaft is a cantilever
Comparison of API 610 VS4 and VS5 Pumps
| Description | VS4 Pump | VS5 Pump |
| Pump Type | The VS4 pumps are Vertically suspended pump with a single casing design and the casing is a volute shape.
These pumps are line shaft driven sump pumps shall be designated pump type VS4. |
Vertically suspended, cantilever sump pumps shall be designated pump type VS5. |
| Line Shaft Bushes | The line shaft bushes are used to support the shaft. Due to this shaft wobbling at high speed will be reduced.
Hence the more depth can be achieved by VS4 pump when compared to VS5 pump. |
The rotor shall be cantilevered from its bearing assembly. Submerged bottom bushings are not used to guide the shaft. |
| Critical Speed limit | VS4 type pumps the first dry critical speed shall be 20% above the maximum allowable continuous speed | VS5 pump the first dry critical speed shall be 30 % above their maximum allowable continuous speed. |
| Shaft Runout Limitation | The shaft runout is limited to 70 μm (TIR) as measured on the shaft directly above the mechanical seal or stuffing box.
The above value is the thumb rule. Usually, it is based on the flexibility factor (Refer to table 17 of API 610) |
The shaft runout shall not exceed 50 μm (TIR) as measured on the shaft directly above the mechanical seal or stuffing box |
Line shaft bushes lubrication |
Usually in VS4 pump either pumping liquid or external clean fluid is used for line shaft bush lubrication. | Due to the absence of line shaft bushes lubrication is not applicable. |
| Pump Length | Pump length up to 10meter is easily available. Some pump manufacturer will able to provide the pump length of more than 10m also. | Maximum pump length is 2 to 3meter. If the pump length more than 3 to 5meter more care should be provided for shaft deflection and wobbling.
If the pump length more than 5meters it is always advisable to select VS4 pumps. |
| Pump Cost for Identical Operating condition | Cost is higher when compared with VS5 | Cost is less when compare with VS4 |