Moeller produces blades vanes buckets nozzle segments locknuts and fluid fittings and specializes in cnc machining and creep feed grinding |
DESCRIPTION
FlexThread™ was created to fill the need for a highly reusable self-locking plug that could be used as a directly interchangeable replacement for standard lockwired type plugs such as MS9902, MS9954, and MS24391 as well as adapted to specialized plugs like shown below. This revolutionary design meets these design goals:
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FUNCTION FlexThread™ achieves remarkable reusability due to its unique and novel design. The locking feature consists of a spring element that exerts an axial force against the threads of the port. Unlike a typical deformed thread, the FlexThread™ spring element distributes the axial force over a comparatively large thread area and the point loading is greatly reduced. Wear is virtually eliminated. Sensitivity to pitch size variation of the mating part is insignificant. There is a consistent prevailing torque generated from cycle-to-cycle and from part-to-part. The spring element is made of Inconel 718 so it is functional from cryogenic to considerably elevated temperatures. It is compatible with fuel, oil, hydraulic and brake fluids, and mating threads made of stainless steels and nickel alloys. PERFORMANCE The FlexThread™ performance can be visualized by plotting the prevailing (locking) torque readings obtained during high cycle reuse testing. This testing is typically done at room temperature and/or at an elevated temperature. The graphs shown below are qualification testing data for size -07 FlexThread™ borescope plugs (.625-18 thread size). The vertical bars represent the torque in inch-pounds. The customer requirement was 30 cycles at room temperature and 30 cycles with a heat soak at 600°F between every cycle. These plugs were intended for use in the fan frame (room temperature) and compressor (600°F) of a commercial aircraft turbofan engine. The prevailing torque had to be within 20 - 50 in-lb and different plugs may be used for the room temperature and elevated temperature tests. | |||||||||
Room Temp - 30 Cycles Lubricant: graphite grease |
600°F - 30 Cycles Lubricant: graphite grease | ||||||||
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We opted to use the same plug for both tests and performed the 30 cycles at room temperature and then 30 more at 600°F. Following completion of these reuse tests, the plug and mating port was still serviceable. Then we performed an additional 30 cycles at room temperature. The graph for that test is here. Again, the prevailing torque was within the specified 20 - 50 in-lb range and the plug and port still exhibited only minimal wear. The FlexThread™ plug was still functional after 90 cycles and exceeded the customer's reusability requirements by 200%.
The test results reported here are consistent with the many tests performed to date. In all cases the FlexThread™ components exceeded the required number of reuse cycles and did so with minimal to zero wear. These results demonstrate the robust performance of the FlexThread™ design.
OTHER APPLICATIONS
The FlexThread™ locking feature has been applied to OEM-designed components at request of our customers who needed a drop-in replacement for conventional safety wired and self-locking plug designs. For example, recently several aircraft engine manufacturers had applications requiring a reliable and highly reusable self-locking plug to fit ports in engines already in the field.
One application was for borescope plugs in a fighter aircraft engine. It was found that in service the plugs could reach temperatures in the 750-900°F range. This greatly exceeded the temperature capabilities of the original Vespel© locking elements. Deformed thread type locking plugs were tried next but they were only rated for 5 reuse cycles plus they were prone to thread seizure. The OEM then proposed safety wiring the plugs but access in the aircraft was so limited that it was nearly impossible to do.
Another application was for a drain plug which does not reach quite as high temperatures as borescope plugs but is installed in a costly and difficult-to-access oil tank. The drain plug is a high maintenance item which is frequently removed and replaced. Reliable locking and high reusability were obvious requirements. Additionally, the original deformed thread plugs were notorious for galling the threads in the oil tanks, causing their customers expensive repairs and much more expensive aircraft downtime.
In both cases we were able to apply the FlexThread™ locking feature to replacement plugs which conformed to the original plugs' dimensional envelope. No changes were required to the next higher assembly and the FlexThread™ plugs were approved as alternate parts. They eliminated the problems with the original plugs while meeting reusability, maintainability, life cycle cost, and weight goals. Most importantly our customers were able to respond to their customers quickly and effectively with a vastly improved product that exceeded their expectations.
Note: This product is protected by US and international patents | |||||||||
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