Rotary vane

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