Vesconite Pump Bearing Design
| Running clearance in mm required for ambient conditions (20oC) | = 0.0017 x shaft diameter mm + 0.10mm |
| press fit (interference) | =0.0015 x housing diameter mm + 0.10mm |
Bore closure during fitting will be equal to the actual interference fit between bush and housing.
For bushes which are fully machined before fitting |
|
| Machined I.D. (unfitted) | = Shaft diameter + ambient clearance + box closure |
For bushes which are not press fitted, or have the inside diameter machined after fitting, do not add bore closure allowance.
Note: Bushes with expansion gaps require mechanical retention against axial and rotary movement. These can include roll pins, grub screws, retaining rings or canister type bush and case sets. Thinner wall section require less clearance for elevated temperatures.
|
Shaft diameter |
No. of Grooves |
Angle between Grooves |
Groove
Radius |
Groove
Depth |
|
20-30 |
3 |
120o |
R3 |
2.5 |
|
31-50 |
4 |
90o |
R4 |
3 |
|
51-80 |
6 |
60o |
R4 |
3 |
|
81-120 |
6 |
60o |
R5 |
3.5 |
|
121-160 |
8 |
45o |
R6 |
4 |
|
161-200 |
10 |
36o |
R6 |
4 |
Groove depth should not exceed half the wall thickness. Use more grooves or wider grooves if depth must be reduced due to restricted wall thickness. Avoid grooves less than 2.5mm deep as they are easily blocked by sand or coarse debris.
Water lubricated bearings need a reliable flow of fluid to avoid excessive temperature rise. Bearings in pump bowls, pressure fed line shaft and stuffing box bushes have a pressure differential from entry to exit ensuring good fluid flow.
Housing steps, circlips, retaining rings, or keeper plates if used should be located towards the low pressure end of the bush.
Flanged bushes (used in large split case pumps) should have the flange located at the high pressure end.
Suction cover and "wet" lineshaft bushes have little pressure differential and rely on the speed of flow to funnel water through the bearings. Make sure that suction cover bores are open at both ends, or that there is a pressure feed to the bearing.
In all cases, make sure that steps in the housing bore do not block the grooves. The I.D. should be greater than the base diameter of the grooves.
For excessively sandy or abrasive conditions, an external feed with a positive pressure supplying clean water directly to the bearings is recommended.
Extra clearance must be added to ambient clearance for operating temperatures greater than 20oC. For operation up 70oC an interference fit is recommended. Calculate extra clearance required.
| ((O.D.2 -I.D.2) / I.D). | x Temperature Change oC x 0.00006 |
For operation between 70oC and 100oC Vesconite bushes must have an expansion gap. Do not use interference fits above 70oC as the resulting strain and loss of elasticity can result in bushes becoming loose at ambient temperature. For bushes with an expansion gap calculate extra clearance
(O.D. - I.D.) x Temp Change oC x 0.00006.
Expansion gap width = housing diameter (mm) x 3.14 x temperature change oC x 0.00006
The specific formulation and additives are not disclosed. However, we can say that Vesconite standard (dark grey) and Vesconite Hilube (white) contain lubricants well suited for use with stainless steel shafts.
Last updated: Apr 21 2001
