calculation of axial, radial and shock loads on bearings in a centrifugal pump

[KAS147]

we have Nuovo Pignone 8"x15" MSND series 6 stages centrifugal pumps of the following main features:
Capacity range: up to 15,000 gpm (3,500 m³/h)
Differential head: up to 1,150 ft (350 m)
Maximum working pressure: 42 bar (600 psi)
Maximum speed: 4,000 rpm
Maximum operating temperature: 800 °F (430 °C)
we have two sleeve bearings and one tilt pad thrust bearing installed with flooded/forced feed lubrication.

another station of our company has Flowserve argentina supplier 6"x13" DMX - G/8 stages Rated power-1247.3 kW ; Rated RPM - 2981
with rolling element thrust bearings with oil ring lubrication.

I have been asked to study the study and evaluate the prospect of oil ring lubrication in place of forced feed lubrication in our station which means tghe replacement of tilt pad bearing with rolling element tghrust bearings.

to start the bearing selection and analysing process, I amin need of the axial and radial loads on the bearings of our pump. Though I have tried obtaining them from the vendor, the manufacturer and calculating them, I have been so far unsuccessful. I request for the possible help.

 

[hydromech]

axial thrust is the net difference in hydraulic thrust on each side of the impeller + the fluid momentum on the inlet eye of the impeller.

Radial thrust is largely a function of pressure and localised imbalance around the periphery of the impeller.

In each case things such as the wear ring (the seal between inlet and outlet) and whether or not it is radial/axial/labyrinth have a big impact on the level of axial thrust.

The only real way to know the thrust levels is to measure them.

 

[psv1990]

Take the request to the pump supplier. The pumps are designed to have a number of options for the bearings. See if you can get access directly with the companies application engineering departments to discuss your requirements with the experts in the company. The information will not come quickly but you should maintain regular contact untill you receive the information required.

 

[xabichika]

You need to check 3 limitations of bearing selection per API 610 10th ed. Table 9; your MSND pump size is bigger than your DMX.

1. Thrust bearing speed.
2. Bearing life
3. Energy Density

 

[KAS147]

Sure it is, done all that research and calculations already. The energy density formula and all, right. Thanks btw.
We cannot use rolling elements instead of hydrodynamic (tilting pad). I have a validation for that.
But still the question before me remains that whether constant level oil ring lubrication can replace forced feed lubrication or not?
The sleeve bearings are already lubricated by ring oil lubrication, It is only the tilt pad thrust bearing that is getting a pressurized circulating supply(flooded) from the lube oil setup.
I know that ring oil lubrication cannot be used in tilt pad... The only option for lubrication I have come across for tilt pad are 'directed' and 'flooded'. But i have no validation to proove that oil ring is not an option for pivoted bearings.
Rather, there are also other types of thrust bearings but little info. is available about them. whether there is a possible hydrodynamic thrust bearing operable on ring oil lubrication or not, I am unaware of it.

And the final question still remains that whether we can used constant level oil ring in place of force.

It is a request for the possible help.

 

[xabichika]

Hydrodynamic thrust bearing must be lubricated by force feed system.If you want ring oil lubrication you must replace the pivot bearing with thrust ball bearings. Understand that most Pipeline application does not like force feed lubrication.

The replacement of pivot bearing with thrust ball bearing can be done but in my opinion is not easy as shaft modification and new bearing housing are required.

MSND is originally under United Pump and Flowserve has bought United (not all factories) back in 2000 so they have the blue print of MSND. You can contact FLS Technical Service department in your region for the modification.