Speed is good: New cleaning process nets huge gains in efficiency

Published Jan. 9, 2015
By Capt. Matthew Whitaker
76th Propulsion Maintenance Group

TINKER AIR FORCE BASE, Okla. -- Speed is good! That's the phrase that is working its way into the culture of the Oklahoma City Air Logistics Complex. And that is exactly what a dedicated team of engineers in the 76th Propulsion Maintenance Group are taking to heart as they work to bring greater efficiency to the F110 engine line here.

As the muscle behind the F-16 Fighting Falcon, the F110 engine comes equipped with a variable nozzle as a key component to its blistering afterburner. When the engine comes to Tinker for lifecycle maintenance, the outer flaps of this nozzle are in need of repair and must be stripped of their tungsten carbide coating before a new coat can be reapplied in the form of a thermal spray. However, cleaning these titanium flaps is no easy task.

Until recently, PMXG's approved process for stripping these flaps was labor intensive, often requiring multiple iterations to achieve desired results. Through use of a CREST Nickel stripper, coatings were degraded and prepared for media blasting. Unable to sufficiently strip the parts after one attempt, the process was repeated until parts were sufficiently cleaned.

Seeing an opportunity to cut flow days and speed up the process, Ed McLaughlin and Dana Coover from PMXG's Process Engineering Team have been spearheading work to institute a new method, which could spread to other engine lines as well. They have demonstrated that with electrochemical stripping, the reverse process of electroplating,
in Rochelle salt solutions there can be huge gains in efficiency of work performed.

Already used previously to remove material buildup on part fixtures from Tinker's thermal spray processes, Rochelle salt solutions in a tank with electric current can break down and separate certain coatings from the base metal. In order to test this on the F110 outer flaps, experiments were first run in a prototype tank on strips of titanium with and without thermal spray. These test strips showed that coatings could be removed with less time in the tank than the old method and without degrading the base metal.

After the testing was completed on actual F110 parts, the engine's system program office approved the use of Rochelle salts as an alternate means of stripping. This has enabled McLaughlin and Coover to successfully implement this process on the production line, and it is already paying off. The old method of soaking the flaps for 48 hours and blasting them repeatedly averaged 144 hours and 15 flow days. They are now soaked once for only 2.5 hours and blasted clean for a finished product. This dramatic cut in costs and time allows for a current workload of 200 flaps per month. Studying the long term effects of this technique on equipment will take time, but the positive results already speak for themselves.

The hard work of those involved to bring this new stripping method to F110 production is a testament to the ingenuity and initiative that will continue to make Tinker's industrial machine a competitive force in years to come.

Cleaning