Rotary Vane
Casting
Area rounded to reduce stress and breakage thereby reducing the play of the vane.
Surface problem – unable to machine to perfect finish.Concentricity
Pressure
Shear here.Oil will “short-circuit” here
Key/keyway
Able to remove and regrind the circular surface.
Double seals
Internal hole for bolt
Gutter
Grooves for greasing
Specifications
• Maximum oil pressure – 100 bar
• Maximum rudder angle – 2 x 37.5°
• Relief valve setting – 100 bar
• Steering time (35°-0°-30°) – – With one pump – max. 28secs– With two pumps – max. 14secs
• Electric Motor– 52KW– IP54
• Oil capacity– Actuator – 270litres– Pump units – 1950litres– Total – 2220litres
• Pump – Capacity – 430l/min– Relief valve setting – 80 bar– Max. temp. - 70°
Items to check
• Actuator should be checked regularly for the leakages, paintwork, damages etc..
• For continuous undisturbed function of S/G depends on using the specified hydraulic oil and keeping the system clean.
• Yearly– Oil filters of pumps– Stuffing glands
• Every 2nd year– Change hydraulic oil if necessary
• Oil filter – inspection after the first 200hrs– If found with impurities – change filter at short
interval
• Hydraulic pumps – last more than 10 yrs– Worn pump – reduced pumping capacity and
slower speed
• Actuator – lifetime of rotor seals is 5 to 10 years
Angle Limitation
• A circle has 360º.• If the rotary vane was to have 4 vanes,
then 360º/4 = 90º.• 90º - 74º [(35º+2º) x 2] = 16º• Leaving 8º for the vane thickness, which
will be very weak.– Moving vane has to have 2 sets of seals.– Stationary vanes have to have oil passages.– Long vanes will be weak.
Case History
• Rotary vane was hunting.• System checked and oil was found dirty.• Drydocking – Whole rotary vane was
overhauled but the cylindrical body was found worn, including the bottom.
• Machined (side and bottom) but still malfunction.
• New set delivery - 6 months later.• Took 5 days to bed to rudder stock.
Side seal
Original condition with seal intact
Cyl. Wall worn down
Cyl. Wall machined
Seal loses tension
Vane
Base worn Skimmed base
Top cover stays in place therefore seal has clearance on top
Vane
Advantages
• Compact
• Less oil is used
Disadvantages
• Low reliability• Wear and tear more. Seal contact surface more.• Cannot take vertical movement/drop• Vane failure – very difficult to ascertain
– Seal in constant contact – more wear & tear– Suspect leakage
• Sluggishness• Check movement timing – 28seconds
• If high pressure – size is very big