Packing cups manufacturing
A method of manufacturing a packing cup for a hyper-compressor is described. The method comprises the following steps: providing an inner disc ( 25 ), having opposed first front face ( 25 X) and second front face ( 25 Y), a central axial hole ( 18 ) and at least one lubrication-oil duct ( 23 ); autofrettaging the lubrication-oil duct ( 23 ); after autofrettaging, removing a thickness (D) of the inner disc on both faces thereof.
1. A method of manufacturing a packing cup for a hyper-compressor, the method comprising the following steps:
providing an inner disc, having opposed first front face and second front face, a central axial hole, and at least one lubrication-oil duct; said axial hole and said at least one lubrication-oil duct extending from said first front face to said second front face;
autofrettaging said at least one lubrication-oil duct;
after autofrettaging, removing a thickness of said inner disc on both said first front face and said second front face; and
after removing the thickness of said inner disc on both said first front face and said second front face, shrink-fitting said inner disc and an outer disc.
2. The method of claim 1 , wherein a volume of material surrounding said at least one lubrication-oil duct of the manufactured packing cup has a residual equivalent stress which is substantially constant along a direction parallel to an axis of said lubrication-oil duct, starting from said first front face or said second front face along at least a portion of an axial extension of said lubrication-oil duct.
3. The method of claim 2 , wherein said residual equivalent stress fluctuates by 25% or less along a first 10% of said axial extension of said at least one lubrication-oil duct, starting from said first front face and from said second front face.
4. The method of claim 3 , wherein said residual equivalent stress fluctuates by 20% or less along the first 10% of said axial extension of said at least one lubrication-oil duct, starting from said first front face and from said second front face.
5. The method of claim 4 , wherein said residual equivalent stress fluctuates by no more than 15% along the first 10% of said axial extension of said at least one lubrication-oil duct, starting from said first front face and from said second front face.
6. The method of claim 5 , wherein said residual equivalent stress fluctuates by no more than 10% along the first 10% of said axial extension of said at least one lubrication-oil duct, starting from said first front face and from said second front face.
7. The method of claim 1 , wherein between 5% and 30% of an overall axial dimension of said inner disc is removed on each said first front face and said second front face.
8. The method of claim 7 , wherein between 7% and 15% of the overall axial dimension of said inner disc is removed on each said first front face and said second front face.
9. The method of claim 1 , wherein between 1% and 30% of an overall axial dimension of said inner disc is removed on each said first front face and said second front face.
10. The method of claim 1 , wherein a volume of material surrounding said at least one lubrication-oil duct of the manufactured packing cup has a residual compressive hoop stress along an entire axial extension of said lubrication-oil duct; and wherein said residual hoop stress has a first value at a central location, intermediate between said first front face and said second front face.