Inspecting and Assembling a 37° Flared Tube End

37 Degree Flared Fitting

Incorrect installation and assembly of hydraulic fittings are major causes for leakage in hydraulic systems. By preventing leakage in your hydraulic systems, you can avoid unnecessary costs such as:

  • The high price of hydraulic oil
  • Maintenance costs
  • Energy loss
  • System inefficiencies
  • Environmental concerns

37° flared fittings seal systems by employing the use of metal-to-metal contact between the flared tube end and fitting nose. Surface imperfections, improper flaring and excessive tightening are leading causes of system leaks. By following the assembly and installation tips below, you can help prevent hydraulic leakage with 37° flared fittings.

  1. Select seamless or welded and drawn tubing that is fully annealed. The tubing should have a wall thickness suitable to flare 37° fittings.
  2. Cut the tubing squarely within ± 1°.
  3. Deburr the tube to remove surface impurities.
  4. Clean the tube to remove debris which can contaminate the system.
  5. Flare the tubing with hand flaring tools or, preferably, power flaring tools for quicker and consistent results.
  6. Inspect the flare dimensions and look for sealing surface imperfections. Under-flaring reduces the sealing contact and can cause nose collapse. Over-flaring will cause tube nut interference.
  7. Align the tube flare with the fitting nose and pre-tighten the connection. Make sure the tube is the correct length and properly bent.
  8. Tighten the fitting using catalog torque specifications or by using the Flats from Wrench Resistance (FFWR) method. The FFWR method is good way to tighten fittings with plating and surface differences. The tube-fitting connection is tightened by a specified number of wrench flats from the pre-tightened position when the FFWR method is used. Making a reference mark on the fitting nut and body at the properly tightened position is a quick way to verify the connection was tightened.

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Mike Hanley
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