Hydra-Just, a new sealing technology from Garlock Sealing Technologies, Palmyra, N.Y. (garlock.com), is said to be more reliable and durable than mechanical seals, particularly in harsh, abrasive environments. It creates a radial bearingtoface seal rather than an axial end-face seal as in mechanical seal. It also eliminates the possibility of catastrophic seal failures.
In operation, an interlocking Glycon excluder ring blocks process media and forces it to take a torturous route to enter the stuffing box. A barrier ring distributes pressure from a barrier fluid (typically water, though mineral water and compressed air have been used) to hydraulically load and maintain inboard and outboard seals. A combination needle/flowmeter downstream from the discharge flow port maintains pressure on the barrier. The hydraulics basically replace springs in mechanical seals. Because pressure, not flow, activates the seal, it uses minimal amounts of barrier fluid. For example, the flush on a mechanical seal in slurry service typically runs at 3 to 5 gpm. In a similar application, Hydra-Just would need 3 to 5 gallons/hr.
Hydra-Just components never see the process media, just the barrier fluid. In mechanical seals, on the other hand, sealing elements and compression packings contact the process media, so seal components have to contend with abrasive and chemical attack. And bathing Hydra-Just's barrier rings in fluid lets them handle high shaft speeds without thermal breakdown.