Hydraulic oil hoses for sleeve bearing assemblies designed to withstand corrosion attacks

Howden issues improved hydraulic hose design for sleeve bearing assemblies with optimum protection against hydraulic pressure pulsations and corrosion attacks.

The improved hydraulic oil hose design protects the hoses from corrosion attacks, and it is also proven to withstand axial movements and hydraulic pressure pulsations, which have caused hose failures in the past. Naturally, the new hose design can be securely mounted with no risk of twisting the hose as this may result in fatigue and wear of the hoses.

In case flue gas enters the inner tube, the supply oil hose mounted on the rotating oil seal on sleeve bearing assemblies can fail because of stress corrosion of the stainless steel braid. Howden has developed a new hydraulic hose design with the stainless steel braid completely protected against corrosion attacks.

If a cold hydraulic hose is in an environment with flue gas, sulfuric acid may condensate on the outside of the hose. This results in stress corrosion cracking of the braid wire of the hose, and the inside PTFE hose will eventually rupture.

This event can happen if there is a problem with the seal air pressure and flue gas enters the inner tube. In worst cases, it can cause a forced outage of the boiler to change the hose.

Although the braid wire is made of AISI 316 stainless steel, it will crack if exposed to sulfuric acid and stress at the same time. This is particularly the case for high strength wires and the cracks on the braid can be very widespread across the full hose length and not just on a localised area.

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Improved Hydraulic Hoses

Close-up of ruptured hose (left) and magnification of the close-up showing corrosion attacks on the braid wires (right)

The improved design prevents stress corrosion cracking

The new hose design consists of five layers with complete corrosion protection. The hoses are designed to withstand axial movements and pressure pulsations, and they can be mounted to the rotating oil seal with no risk of twisting.

5-layer hose design for optimum protection

  • Inner hose is an anti-static PTFE tube
  • Double layer of AISI 316 stainless steel braid to keep pressure (test pressure 270 bar for supply hose)
  • Silicone cover protects the braids from unnecessary wear
  • PTFE protection hose is corrugated outside to make it flexible and cylindrical inside for durability

New hydraulic hose design

  • The outer PTFE hose guarantees complete protection against sulphuric acid
  • The inner and outer PTFE hoses are tested for leakages to guarantee that sulphuric acid cannot penetrate
  • The improved design is compatible with all previous hose designs
  • AISI 316 fitting
  • Working temperature up to 400°F
  • Pressure tested (test pressure 3900 psi for supply hose)
  • Designed with a separate 90º fitting avoid twisting of hoses when tightened during mounting.

The improved hydraulic oil hose design protects against corrosion attacks, and it can also endure axial movements and hydraulic pressure pulsations inside the Teflon core because the inner hose is smooth bore PTFE and not a steel bellow hose which may develop fatigue cracks.

 
 

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