| Problem |
Common Valve
Weaknesses |
Everlasting
Solution |
Result |
| Seats Wear Out |
Sealing surfaces always meet at the same point (1 to 4) |
Rotating disc/self lapping |
Seats wear in, seal improves with use |
| Leak rate limits exceeded soon after installation |
tight shut-off only at time of installation (1 to 4) |
Rotating disc/self lapping metal to metal seats |
Tight shut-off maintained long after installation |
| Media build-up, drags across seats |
Ineffective seat cleaning (1 to 4) |
Sharp edge, shearing disc against flat metal seat |
Media build-up sheared from sealing surfaces |
| Flow causes erosion across seating surfaces |
Narrow seat band in line with flow (1,2,3) |
Wide seat band perpendicular to flow |
Erosion in flow path does not affect sealing ability |
| Loss of product through packing gland or top seal |
Stem scores packing or vulnerable "O" ring (1 to 4) |
Spring loaded packing and non-rising rotating stem |
Reduced maintenance hours, efficient operation |
| Thermal Lock-up |
Intolerance to different expansion rates (1 to 4) |
Disc drive to disc is spring loaded |
Constant yield to thermal stress and shock |
| Excessive pressure drop and reduced flow |
Flow path restricted when valve is open (1,2,3) |
Full port flow |
No obstruction to flow, downsizing possible |
(1) Ball Valve (reduced port)
(2)
Plug Valve
(3) Butterfly Valve
(4) Gate Valve |
