WIND TURBINE HYDRAULIC SYSTEM:OPERATION AND MAINTENANCE

OutlineIntroduction to turbine hydraulic systemDescription/Location of hydraulic systemWind turbine hydraulic oilWind turbine hydraulic filters and filtration elementsFlow and pressure control valvesPumps/motors, cylinders, and accumulatorsWind Turbine Hydraulic SystemBlade pitch controlDistributor and Membrane blocksRotating jointRotor brakeYaw system brake clampsHydraulic system schematicsHydraulic system maintenanceGeneral considerationsCommon maintenance issues/Troubleshooting/Solutions

What is Hydraulics?The pressure in a static hydraulic fluid in a closed system is the same everywhere.If the ratio of the areas is 5, a force of 100 N on small piston will produce 500 N of force on large piston.However, small piston must move 50cm to in order to raise the large piston 10cm => Law of conservation of energy.

Description/Location

Description/Location

Description/Location

Description/Location

Wind Turbine Hydraulic Oils5 main tasks of hydraulic oil in the wind turbine;To transfer hydraulic energyTo lubricate all partsTo avoid corrosionTo remove impurities and abrasionTo dissipate heat.

Physical properties to consider;Viscosity index => increased viscosity at lower tempsShear and thermal stability => longer service timeUsable temperature rangeUsable pressure rangeDetergency => prevents depositing of contaminants

Wind Turbine Hydraulic OilsViscosity is single most important selection factor for the turbine hydraulic oil. Based on;Starting viscosity at minimum ambient temperatureMaximum expected operating temperature, which is influenced by maximum ambient temperaturePermissible and optimum viscosity range for the systems components

Wind Turbine Hydraulic OilsThe gamesa turbine hydraulic group uses 1 of three hydraulic oil types;Texaco Rando HDZ 32Minimum viscosity change over large temperature rangeMeets all major pump manufacturer requirementsFuchs Renolin HV1 32 GAShell Tellus T32Mineral hydraulic oilSuitable for ultra-fine filtration

315 L required for G8X Platform and expected service life is 5 yearsOil level alarm goes off at 130 to 140 L

Wind Turbine Hydraulic OilsWhat happens if hydraulic oil is allowed to circulate at a hightemperature for a long period of time?As temperature goes up, hydraulic oil viscosity goes down.Low viscosity results in the failure of the oil to maintain a lubricating film between the internal parts of the system.

Oil will need replacing as high temperature will have destroyed it.Cylinder seals can be destroyed => expensive, downtimeFailure of hydraulic motor pistons => expensive

Imperative that high oil temperatures be avoided

Wind Turbine Hydraulic Oils Water ContaminationWater contamination can affect the following properites;ViscosityLubrication capacity and load-carrying characteristics.Power transfer characteristics (compressibility).

Wind Turbine Hydraulic Filters and Filtration ElementsTurbine hydraulic filter must meet the following performance requirements;Capable of reducing the initial contamination to desired level within an acceptable period of time.Must achieve and maintain level with a suitable safety factor.Easily accessible for maintenance.Must provide sufficient dirt-holding capacity for an acceptable interval between element changes.Must not produce undesirable effects on the operation of components, such as high back pressures.

NacelleHub

Wind Turbine Hydraulic Filters and Filtration ElementsGenerally reccomended that at least a 25 micron (1 micron = 0.000039 inches) range be used for a hydraulic system.G8X platform uses a 10 micron filter and a 3 micron filter (1 red blood cell is 8 microns in diameter).To satisfy performance requirements, must consider;Degree of filtrationFlow ratePressure dropDirt capacitySystem PressureTemperature3 microns10 microns

Wind Turbine Hydraulic Filters and Filtration ElementsG8X hydraulic system uses a pressure filter to remove oil contamination.

Wind Turbine Hydraulic Filters and Filtration Elements

Wind Turbine Hydraulic Filters and Filtration Elements

Wind Turbine Hydraulic Filters and Filtration Elements

Wind Turbine Hydraulic Filters and Filtration ElementsG8X hydraulic system nacelle pressure filter and hub pressure filter are changed every 12 months.Each changed whenever the hydraulic oil is replaced.Nacelle filter changed if the fall in pressure between the pressure sampling ports on either side of the filter exceeds the values given in the following table.Pressure Sampling port

Wind Turbine Hydraulic Filters and Filtration ElementsIndicators for hydraulic filter changePressure differences across the filtration elementIf pressure is erratic in system then passage through the filter is being restricted. Very likely there is contamination in the hydraulic fluid and hence the filter => replace filter.Hydraulic Oil TemperatureOil viscosity will breakdown and lubrication will be less causing contamination of system and hence the filters => replace filters along with oil

Wind Turbine Hydraulic Filters and Filtration Elements

Flow and Pressure Control ValvesFlow Control ValvesRegulate flow or pressure of the hydraulic oil.Respond to signals generated by devices such as flow meters or temperature guages.

Pressue Control ValvesLimit maximum system pressure as a safety measure.Unload system pressure.Operate on balance between pressure and mechanical load.Valve can be fully opened depending on a pressure differential.

Flow and Pressure Control ValvesSolenoid Valve: Also called an electrochemical valve. 14 are present in the hydraulic system (4 on each pitch block (12 total), 1 on rotor brake block, and 1 on yaw brake block).Controls the flow of oil by opening and closing via an electric current => similar to a light switch but for liquids.A- Input side B- Diaphragm C- Pressure chamber D- Pressure relief conduit E- Solenoid F- Output side If solenoid in E is activated by an electric current it will raise and water from C will flow through D and the pressure in C will be reduced and the diaphragm will lift and oil will flow from A to F.Solenoid valve working

Flow and Pressure Control ValvesNeedle valve (butterfly valve): flow control valve. Can regulate flow very precisely. Untilneedle is completely retracted, flow is impeded significantly.Pressure relief valve: used to control or limit pressure in system. Prevents overloading. Oncesystem reaches reset pressure, the valve will close.Check valve (anti return vavle): allows flow in only on direction. Function like a heart valve. Allows the resevoir (accumulator) to maintain pressure when system is inactive.Pressure Relief Valve video

Flow and Pressure Control ValvesIndicators of pressure relief valve malfunction

Poor filtration can lead to damage of any valve in the system.

Pumps/Motors, Cylinders, and AccumulatorsPump/Motor SystemPump-motor sits on top of the resevoir while the pump is located below inside the resevoir.Pump creates a minimum pressure of 180 bar and maximum pressure of 200 bar in the system.

Pumps/Motors, Cylinders, and AccumulatorsTurbine hydraulic pump is a positive displacment type pump.A relief valve will be located after the high pressure outlet to regulate pressure in system.Turbine hydraulic system also contains a relief valve after the high pressure outlet to prevent cavitation in the circuit.Cavitation: when fluid does not entirely fill the space provided for it in the pump => air cavities which implode when the encounter a high pressure area.

Pumps/Motors, Cylinders, and AccumulatorsPump/Motor problemsInsufficient pressureRelief valve not properly set.Excessive pump noisePump-motor misalignment.Low oil level.Wrong oil type.System Excessively hotPump operated at higher pressure than required.Inadequate cooling provided by cooling system.Oil low in resevoir => leaks.

Pumps/Motors, Cylinders, and AccumulatorsSingle rod cylinders located in turbine hub

Pumps/Motors, Cylinders, and AccumulatorsMust limit the extension speed (pressure) of the cylinders.Force in the cylinder is equal to pressure times the area.If the pressure rating of the cylinder is for some reason exceeded, the consequences can be serious.Following video demonstrates cylinder function in a simple hydraulic circuit as well as what can happen when the pressure rating is exceeded when the flow is managed incorrectly.Single rod cylinder extensionCylinder extension has a typical sound as does cylinder retraction.Differences in sounds indicate some type of cylinder failure.

Pumps/Motors, Cylinders, and AccumulatorsCylinder Failures/ProblemsCylinder seal malfunctionImproper installationHydraulic system contaminationChemical breakdown of the seal => poor seal selectionHeat degredationDiesel effect air passes through seals and mixes with hydaulic fluid and explodes when pressurized.Bent cylinder rodsPoor design => insufficient rod diamterImproper cylinder mountingCylinder tube ballooningTube material unable to withstand operating pressure

Pumps/Motors, Cylinders, and AccumulatorsPrinciple accumulator 32 LRotor brake accumulator 4L (behind motor in photo)Principle rotor accumulator 20L (not seen)3 Pitch accumulators 3.5LYaw accumulator 3.5L

Pumps/Motors, Cylinders, and AccumulatorsFunctions as an energy storage device.Held under pressure by an external source => nitrogenAllows for system to cope with large demands => better than using a larger pumpSystem can respond quickly to temporary demand and smooth pulsations.

Pumps/Motors, Cylinders, and Accumulators

Pumps/Motors, Cylinders, and AccumulatorsBladder failure is one of the most common accumulator problems.Various types of bladder material cuts and tears caused by; rapid precharging, little or no precharging, folding of bladder bottom during replacement, lack of lubrication on the bladderFluid contamination can cause debris entrapment between bladder and wall during cycling => good filtration necessary.Gas valve leakingDirt can get into the gas valve stem keeping the valve core from sealing.

Hydraulic Group GeneralSafety ConsiderationsWorking with a large volume of oilSpillsEye/skin irritationWorking with high pressuresSpillsPossible explosion risksMovement of pitch cylinders while doing preventive maintance in the hubTrappingHigh pressures must be respected and the deviceshandling the high pressures must be understood.

Hydraulic System SchematicsNACELLEHUBblade cylinderretractionblade cylinderextensionblade cylinderemergencymembraneblockPrimary pump,accumulator, resevoirrotor brakeyaw brakecoolingdistributor block

Hydraulic System Schematics Common Symbols

Continuous line (flow line)

Circle As a rule, energy conversion units(pump, compressor, motor

Squares As a rule, control valves (valve) except for non-return valves

Diamond Conditioning apparatus(filter, separator, lubricator, heat exchanger

Restriction (affected by viscosity)

Solid Direction of Hydraulic Fluid

Pump One direction of flow

Hydraulic System Schematics Common Symbols

Sloping arrow -indication of the possibility of the regulation or a progressive(proportional)variability.

Cylinder - Returned by unspecified force cylinder in which the fluid pressure always acts in one and the same direction on the extension stroke.

Single square indicates a unit that controls flow or pressure (having an infinite number of possible positions that would vary the conditions of flow across one or more of its ports, ensuring the chosen pressure and/or flow dependingon the operating conditions of the circuit) Two squares indicates a directional control valve with two positions (would show flow paths through ports in actual application)

One flow path Two closed ports Two flow paths Two flow paths and one closed port

Two position would have distinct circuit conditions shown in each square

Free opens if the inlet pressure is higher than the outlet pressure

Hydraulic System Schematics Common SymbolsHydraulic symbol videos

One normally closed throttling orifice (general symbol)

Electric motor

Accumulator - The fluid is maintained under pressure by a spring, weight or compressed gas (air, nitrogen, etc.)

Not showing coolant flow the arrows indicate the extraction of heat

Hydraulic System Schematics Filling of Principle Accumulator Positions 2, 5, 6, 7, 8 form the pump motor group. Position 22 is 3 micron pressure filter.Position 23 is a pressure transductor that sends the actual pressure to the PLC.Postion 4 is an antireturn or check valve to ensure that oil does not flow back from the accumulator to the pump.Position 25 is a safety valve that opens when 225 bar is reached and returns oil to the tank.9.1 is the system thermometer and 9.2 is the tank level detector.

Hydraulic System Schematics Filling of Principle Accumulator

Hydraulic System Schematics Filling of Principle Accumulator

Hydraulic System Schematics Rotor BrakeRotor brake system is supplied from the main hydraulic group via a reduction valve.Circuit passes through a check valve and loads the brake accumulator and braking can be assured without pressure from the principle accumulator or the princple hub accumulator.

Hydraulic System Schematics Rotor Brake

Hydraulic System Schematics Rotor Brake

Hydraulic System Schematics Yaw System BrakeHydraulic system provides braking or clamping of the yaw system in order to maintain its position once set.Similar to the rotor brake, yaw system has its own accumlator which maintains pressure in the yaw brake system.

Hydraulic System Schematics Yaw System Brake

Hydraulic System Schematics Yaw System Brake102- ANTI-RETURN VALVE. ALLOWS ENTERY OF THE OIL INTO THE YAW CIRCUIT AND THE ACCUMULATOR IS FILLED. THE VALVE NUMBER 103 SHOULD BE CLOSED.104- VALVE TO LIMIT THE PRESSURE (230 bar)105- WHERE THE PRESSURE OF THE CIRCUIT IS MEASURED.108- PRESSURE TRANSDUCTOR. IT MEASURES THE PRESSURE IN THE CLAMPS WHEN THE TURBINE IS ORIENTING ITSELF, THE VALVE 109 IS ACTIVATED. VALVE 110 REDUCES THE PRESSURE TO 200 BAR (20 BAR)

Hydraulic System Schematics Yaw System Brake

Rotating JointConnects the main hydraulic unit in the nacelle to the pitch control hydraulic system in the rotor.Rotor electrical equipment runs through this joint as well.Composed of a high pressure line and a low pressure return line.Connection between the pipes is mobile and the circuit leading to the rotor is composed a double-channel rotating joint fitted behind the gearbox.PS channel (3/4 inch): pressure channel from hydraulic groupTS channel (1 inch): return channel for oil return.DS channel (1/2 inch): drainage channel to reconduct leaks.Electrical channel (18 mm): carries electrical cables.

Rotating Joint

Rotating Joint

Two hydrauliclines and oneelectrical line enterinto the hub fromthe rotating joint.

Distributor Block and Membrane Block Distributor block feeds pitch system. Membrane block is inactive until there is a blockagein return line through rotating joint. In this event, circuit is directed to membrane blockand oil sent to a resevoir.

Hydraulic System Schematics -Distributor Block Located in hub in order to reduce the distance travelled through the rotating joint. Acumulator (pos 74) at 143 bar From here, pressure will moveto the pitch system hydraulics 10 micron filter is used in this block in order to avoid contamination that may enter from the rotating joint

Hydraulic System Schematics -Distributor Block

Membrane Block4 lines connecting to drainage tank, 1 givingoil in the event of blockage in the line and1 from the return from each cylinderin the event of blockage in the rotating joint.

Hydraulic System Schematics -MEMBRANE BLOCK Only used when blockage in thethe rotating joint is detected. When blockage occurs, membrane in position 76 breaks and oil flows to 70 L overflow tank (postion 51) 4 lines lead into overflow tank from block 1 from blockage in the rotating joint. 3 from each cylinder in the pitch system

Hydraulic System Schematics -Membrane Block

Blade Pitch ControlMultiple distributor block => contains the valves that control the movement of each cylinder.3 accumulators for each block as well as one principle accumulator (in distributor block) for entire pitch control system.Membrane block that, in the event of a rotating joint blockage on the return line from pitch system, sends the oil to a storage tank.The function of the block is to maintain a circuit so as to prevent rupture in the principle circuit.Proportional valve controls cylinder, depending on the recieved operation signal.Main parts of the pitch control system hydraulic circuit;

Blade Pitch Control

Blade Pitch ControlExtension or retraction of thecylinder will rotate the bladebetween ~0 degrees and 90 degrees (with respect to thetower).

Blade Pitch Control Proportional ValveControlled by electronic control boards.Sometimes called electro-hydraulics.Can control direction and the amount of fluid or can control the amount of pressure in a system.Useful in situations;Where system speed must be tightly controlled.Where ramping up and down is needed to avoid sudden stops and starts.When precise control of hydraulic pressure build up is necessary.

Blade Pitch Control Proportional ValveValve works on theprinciple of doublefeedback control.Feedback comesfrom valve itself (position) and fromballuf (cylinderposition).

Blade Pitch Control Proportional ValveNo flow - EmergencyNormal Flow Cylinder ExtensionFlows criss-crossed Cylinder RetractionProportional valve function

PITCH SYSTEMCASE 1: Cylinder Retraction Oil enters and follows circuit in red (pressurized) and flows out of system (blue) Retraction circuit is activated upon activation of the proportional valve at postion 82. Anti return valve at postion 96 does not function as oil flows in the opposite direction the valve will function in.

PITCH SYSTEMCASE 2: Cylinder Extension For cylinder extenstion, oil is recycled through proportional valve. Anti return valve at position 96 forces oil back to postion 84.2 and oil is recirculated.

PITCH SYSTEMCASE 3: Emergency When in emergency, valves 82, 83.2, and 83.1 all close. Solenoid valves at 81.2 and 81.1 open. Load control valve at position 90 then comesinto contact with pressurized oil. This valve ensures there is enough pressure to counter act the force of the wind while in emergency.

Hydraulic System Schematics -Pitch System

Hydraulic System Schematics -Pitch System81.1, 81.2 Energized = no flowDe-energized = allow flow

83.1, 83.2Energized = allow flowDe-energized = no flow

Accumulator 87 ensures there is sufficient oil to pitch blades to 90 as24 and 74 will be discharged.Accumulator 94 absorbs pressureshocks from valve 90.Accumlator 93 delivers pressureto return oil when in emergency.

Hydraulic System Schematics -Pitch System

Hydraulic System Schematics -Pitch System

Hydraulic System Schematics -Pitch System

Hydraulic System Maintenance General Considerations/CommentsVery robust design.System is always running between 180 and 200 bar

When there is no pressure in the system, first step in determining cause is to start system and listen.Air filter for cooling system must remain clean.Holes in system can only knock out pressure if they occur in certain areas.time180 bar200 bar

Hydraulic System Maintenance General Considerations/CommentsOne very good method to detect turbine hydraulic problems => remote monitoring of turbine hydraulic systems.e.g. if one turbine in the park is running an oil temperature of 56 C and the rest are running at 42 C..Due to electrical control of solenoid and proportional valves, often times a hydraulic problem is often in reality an electrical problem.Proportional valves and solenoid valves are electrical as well as hydraulic so care must be taken when working with them => cut current to them.So far there has been no case of hydraulic hosing breaking in field.

Hydraulic System Maintenance General Considerations/CommentsIn Vestas turbines, the yaw brake is an completely separate hydraulic system.Yaw hydrualic block is the same in both G5X and G8X turbines.6mm steel tubing from yaw block is very resistant against high pressures but can be easily damaged by outside mechanical force => someones foot!

Hydraulic System Maintenance Common Problems/Troubleshooting/SolutionsDont change the oil, filter it.Water or particle contamination rarely necessitates an oil change unless it results in additive depletion or base oil degredation.If the oil maintains its chemical and viscoelastic integrity, then the filter should take care of all contaminationso long as the filter is properly maintained.

Hydraulic System Maintenance Common Problems/Troubleshooting/SolutionsEliminate particle contamination to reduce breakdowns.ISO 4406 is a measure of hydraulic fluid cleanlinesss.

Research has shown that an ISO 4406 level of 16/14/11 will result in a tenfold decrease in average time between breakdowns when compared to a level of 24/22/19 (3 year study)

Hydraulic System Maintenance Common Problems/Troubleshooting/SolutionsParticle contamination reduces fluid life by stripping additives and promoting oxidation.Additives attach to particles with then are removed by filtration or settle to the bottom of the resevoir.Worn metal can act as a catalyst for fluid oxidation.Keep the fluid cool.High temperatures promote fluid oxidation.Oxidation products such as varnish and sludge can plug filters and valves.

Hydraulic System Maintenance Common Problems/Troubleshooting/Solutions6 routines must be followed in order to minimize hydraulic system failure;Maintain fluid cleanlinessMaintain fluid temperature and viscosity within optimum limitsMaintain hydraulic system settings to manufacturers specificationsSchedule component change-outs before they failFollow correct commissioining proceduresConduct failure analysis.

Effective program requires time, effort and expense but is cost effective => investment is quickly recovered!

Hydraulic System Maintenance Common Problems/Troubleshooting/SolutionsSafety bulletin