Standing Up to Hydraulic Fluid: Hose for Engine Test Stands

05 August 16

Students of the scientific method know how important it is to have only one variable at a time when conducting testing. Sometimes that “single” variable is a complex machine, but faulty or inadequate components should never be a variable when developing high-tech engines.

Automotive, aeronautic, and aerospace engines go through extensive testing not only to verify that they function, but also to optimize and improve performance and develop new features and capabilities over time. It wouldn’t do to test untested products, new features, and optimizations only “in the wild” (as in, in motion)—especially in airplanes and anything that navigates off the ground. So engine test stands enable engineers and mechanics to isolate just the engine and its components for testing. But for the tests to be effective and valid, supplies like hydraulic hose must do their job silently—capably transferring fluid without compromising the system.

In the case of aviation engine test stands, hydraulic hose has to stand up to Skydrol, a phosphate-ester hydraulic fluid used in aircraft because of its low flammability, but which is caustic and corrosive to rubber. While rubber hose is an inexpensive and readily replaceable option, the high failure rate causes interruptions and testing down time, but the corrosive interaction with the Skydrol can contaminate the fluid and impact the purity of the test results. So for a client of US Hose Corporation (a United Flexible company), a hose product that not only lasts longer but also maintains the integrity of the testing environment is critical.

This better hose option has to be:

  • Flexible—the hose will connect various components and may be moved between components throughout the testing phase, so a rigid or fixed solution isn’t appropriate
  • Compatible with high pressure—tests will aim to push the limits of equipment, pumping Skydrol through the engine at varying pressures, so the hose’s pressure handling should exceed what will be tested
  • Non-reactive—Skydrol’s corrosive properties interact with rubber and elastomers, creating blistering, sweating, and degrading, also leading to test contamination, do the hose solution should eliminate this problem and be replaceable before failure

US Hose Corporation (a United Flexible company) engineers recommend Dense-Pak or Ultra Fluoropolymer hoses for test stand applications. These high pressure hoses feature a PTFE or PFA inner core that does not degrade with exposure to Skydrol/phosphate-ester hydraulic fluids or allow contaminating seepage or leaks due to failure. These hose products are also flexible and manufactured to handle high pressure with stainless steel braided exteriors. Our aviation clients have found these products to exceed their needs for a safe, efficient, and pure engine testing environment.

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