Centrifugal pump with mechanical seal arrangement

A centrifugal pump capable of pumping a fluid, said pump comprising:

• a centrifugal pump casing having an intake plate forming an intake port, a pump outlet, and a back section forming a seal chamber extending rearwardly from a central opening formed in a radially extending wall of the back section;
• a drive shaft extending into said casing and through said central opening from a rear side of said casing, said drive shaft being rotatable about an axis of rotation in a selected direction of rotation;
• an open impeller mounted on said drive shaft for rotation therewith, said impeller having radially extending vanes each having a leading edge that extends generally radially in relation to said axis of rotation and each having a trailing edge with a substantially open, circumferentially extending gap between adjacent trailing edges of these vanes;
• and
• a mechanical seal mechanism comprising a seal cartridge mounted in said seal chamber, said seal mechanism having a rotating component mounted on said drive shaft and a stationary component mounted on said back section, said rotating component including a central sleeve adapted to and sized to be mounted on said drive shaft for rotation therewith, a seal support mounted on said sleeve for rotation therewith, and an annular first seat mounted on said seal support, said stationary component comprising an annular flange member having a radially extending flange, an annular seat housing, an annular second seat mounted on said seat housing adjacent said first seat, and a spring extending between said seat housing and said flange on said flange member and pressing said second seat against said first seat in order to provide a mechanical seal by maintaining a closing pressure sufficient to keep adjacent faces of the first and second seats together, said seal chamber having a circumferentially extending wall extending around at least a forward portion of said seal mechanism and spaced therefrom so as to form an open annular space exposed to the pump fluid for circulation of a portion of said fluid, said circumferentially extending wall converging in a front to rear axial direction,
• wherein during operation of said pump, said seal mechanism effectively seals an annular gap between said drive shaft and said back section while being lubricated and cooled by said portion of said fluid being pumped by the pump.

A centrifugal chopper pump capable of pumping a fluid containing a solid material, said pump comprising:

• a pump casing having a frontal intake port, a pump outlet in a side thereof, and a back plate structure forming a central seal chamber extending rearwardly from an open front end of the chamber;
• a rotatable drive shaft extending into said casing and through the seal chamber from a rear side of said casing, said drive shaft being rotatable about an axis of rotation in a selected direction of rotation;
• an open impeller mounted on said drive shaft for rotation therewith, said impeller having radially extending vanes each having a leading edge that extends generally radially in relation to said axis of rotation and each having a trailing edge with a substantially open, circumferentially extending gap between adjacent trailing edges of the vanes;
• a cutting mechanism mounted in said pump casing and co-operating with said impeller during use of said pump to cut up incoming solid material;
• and a mechanical seal cartridge mounted in said back plate structure and on said drive shaft so as to close and seal an annular gap between said drive shaft and said back plate structure while leaving open a front portion of said seal chamber which is exposed to the pump fluid so that the seal cartridge is lubricated and cooled by a portion of said fluid circulating in said front portion during use of the chopper pump, said seal cartridge including an inner sleeve mounted on said drive shaft, rotatable and stationary seats, a coil spring mounted on and extending around said inner sleeve and mounted so as to press said stationary seat against said rotatable seat, and an annular shroud arrangement covering the circumferential exterior of said coil spring so that said solid material is kept substantially away from contact with said spring.