New bulkhead shaft seal using "Smart" Hydroactive Gel Technology developed for, and used by the US Navy is ready to go commercial. The seal was developed in response to a US Navy request after existing bulkhead shaft seal deficiencies were exposed following the USS Cole incident.
Medford, MA (Vocus) November 19, 2009 -- The bulkhead shaft seal, designed to prevent flooding between compartments along the main propulsion shaft, failed catastrophically when the USS Cole was attacked in Aden in 2000. Subsequent US Navy inspections concluded that their nominally rotating seals were being consistently activated prematurely, leading to early and excessive wear, and preventing the seals from fulfilling their intended purpose. A new design was sought.
Midé Technology (Medford, Massachusetts), in response to the US Navy’s request, has successfully designed, developed, tested, and installed non-rotating bulkhead shaft seals on US Navy ships. Following the successful adoption of the Hydroactive bulkhead shaft seals, Midé now int to offer it on a commercial basis. Andrew Cutler, Director of Systems Development at Midé offered, “from tugboats to tankers, this smart seal technology has unlimited benefits for both Naval and Commercial shipping”. One major advantage over existing seals is the employment of innovative “smart” hydrogel technology.
Midé’s President, Dave Gilbert stated, “This non-rotating, smart hydrogel seal does not contact the shaft during normal operation, and only activates when exposed to water. It’s sealing force actually increases as water pressure increases”. Additional tests confirmed that the seal, when engaged, enabled shaft operation for a minimum of 14 days when a compartment is flooded, without any limitations on shaft speeds.
In the absence of water, the seal resets itself, allowing repeated use without maintenance or replacement. Since the seal is stationary with respect to the shaft, and nominally not in contact with the shaft, it has excellent wear characteristics, thus offering a significant “life cycle cost” advantage over competing designs, along with the safety value it offers its host ship. The design also allows shaft / bulkhead alignment requirements to be eased, which will lead to substantial shipbuilding cost savings.
Extensive performance, shock (MIL-S-901D, Grade A), vibration (MIL_STD-167-1A) and sea-trial testing concluded that the Midé seals outperform competitor designs with leak rates substantially less than the Navy’s allowable leak rate of 1 US pint/minute.
Currently, Midé’s patent pending design is approved for both forward and retrofits on the Arleigh Burke (DDG-51) class destroyers and is installed on several DDG-51 ships. The seals, which accommodate a 20 ?” diameter shaft, are designed as a “drop-in” replacement for the currently installed, failing diaphragms. A novel “Yoke” design offers significant cost and weight saving has completed qualification testing for a 10” (254mm) shaft size while testing on a 29.92” (760mm) shaft size unit is in progress. This design eliminates the need for a heavy housing and allows for installation without the need for riggers.
After qualification of the 29.92” unit, Midé will offer a full range of bulkhead shaft seals, and stern tube seals in the not too distant future, a boon for both the navy and commercial shipping alike.
If you’d like more information about this topic please visit our website (www.mide.com), or to schedule an interview with David Gilbert, please call 781/306-0609 ext 224.
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