Spiral groove seal system for high vapor-pressure liquids

A tandem seal system for sealing a shaft extending through a housing against leakage of a high vapor-pressure liquid, comprising:

• an upstream module mounted on the shaft and housing including means for effecting a phase change of the sealed liquid from liquid to gas as it passes through said module, said means for effecting a phase change including a seal having a primary ring affixed to the housing and a mating ring affixed to the shaft, the rings having opposed, radially extending faces, one of which a plurality of downstream pumping spiral grooves extending from one circumference thereof,
• a downstream module mounted on the shaft and housing downstream of the upstream module, the downstream seal module comprising a seal having a primary ring affixed to the housing and a mating ring affixed to the shaft, the rings having opposed, radially extending faces, one of which has a plurality of downstream pumping spiral grooves extending from one circumference thereof, the grooves of said upstream module seal being of a depth which is less than the depth of the grooves of said seal of said downstream seal;
• and a vent passage in fluid communication with the downstream module and connectable to a combustion means.

A method of sealing a rotatable shaft extending through a housing against leakage of a high vapor-pressure liquid comprising the steps of

• providing a first barrier to the flow one liquid along said shaft,
• said first barrier having a first radially extending seal face with a plurality of pumping spiral grooves, said first seal face grooves having a first predetermined depth, allowing a portion of said fluid to escape across said barrier, and
• providing a second barrier to the flow of fluid along said shaft, said second barrier having a second radially extending seal face with a plurality of pumping spiral grooves, said second seal face grooves having a second predetermined depth greater than said first predetermined depth.

A tandem spiral groove seal system for sealing a rotatable shaft extending through a housing against leakage of a fluid, the system comprising:

• (a) a first upstream module including a primary ring sealingly affixed to the housing and a mating ring affixed to the shaft, the rings having opposed, radially extending faces, one of which has a plurality of pumping spiral grooves extending from one circumference of the face, said spiral grooves of said first module seal face having a first predetermined depth;
• and
• (b) a second downstream module spaced apart from said first module, said second module including a primary ring sealingly affixed to the housing and a mating ring affixed to the shaft, the rings having opposed, radially extending faces, one of which has a plurality of pumping spiral grooves extending from one circumference of the face, said spiral grooves of said second module seal face having a second predetermined depth which is greater than said first predetermined depth of said first module seal spiral grooves.

A method for sealing a shaft extending through a housing against leakage of sealed fluids comprising:

• providing an upstream mounted on the shaft and housing for sealing said sealed fluid, said upstream seal module comprising a seal having a primary ring affixed to the housing and a mating ring affixed to the shaft, the rings having opposed, radially extending faces, one of which has a plurality of upstream pumping spiral grooves extending from one circumference thereof, said upstream pumping spiral grooves having a first predetermined groove depth;
• providing a downstream module mounted on the shaft and housing downstream of the upstream module, the downstream seal module comprising a seal having a primary ring affixed to the housing and a mating ring affixed to the shaft, the rings having opposed, radially extending faces, one of which has a plurality of downstream pumping spiral grooves extending from one circumference thereof, said downstream pumping spiral grooves having a second predetermined groove depth which is greater said first predetermined groove depth of said upstream pumping spiral grooves.