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Grease Leakage Analysis and Improvement Measures of Wind Turbine Pitch Bearing (1)

2021-07-30 14:29

Causes of grease leakage of pitch bearing

 

1 Poor sealing

Aging and Wear of 1.1 Sealing Ring

Pitch bearings are mostly usednitrile rubberSealing ring,Long timeThe aging rate is the same as that of the propylene in the nitrile rubber.The content of enitrile, the gum content of the formula, the anti-aging agent and the use environment.In general, the service life of Ding Qing rubber sealing ring is5 to 10 years. Pitch bearing usedcontact seal, in the running processThe contact between the middle sealing ring and the sealing friction surface increases as the running time increases.Plus, the sealing ring will gradually wear out, resulting in a decrease in sealing performance and sealingInsufficient ring pressure, grease may leak from the sealing ring.

 

Unreasonable structural design of 1.2 sealing ring

Pitch bearings are generally usedDouble-lip sealing ring, its outer lip can be blockedIntrusion of moisture, dust and other harmful substances into the bearing, inner lipCan prevent grease leakage. If the seal ring structure design is unreasonable, after installationThe sealing effect is affected and the pitch bearing may be guided after operation.Deformation of sealing ring, insufficient sealing capacity or sealing failure, lubricationGrease leaks easily.

 

1.3 Improper installation and maintenance of sealing ring

When not installed or maintained according to the process, the sealing ring will be stressed.Uneven, poor bonding of the interface when installing the sealing ring will cause sealingThe ring interface is broken, and the sealing ring capacity after the subsequent pitch bearing greasing operationEasy to appear bulge, warping and fracture phenomenon, so that lubricationThe grease overflows from the gap, warping and damage of the sealing ring.

Crush damage of 1.4 sealing ring

 

The blades of wind turbines need to be used during installation or maintenance.Hydraulic tensioner applies force to blade and pitch bearing attachment boltMoment, the distance between the connecting bolt and the sealing ring is close, andHydraulic TensionerThe size of the stretching head is larger,The stretching head is easy to press to the sealing ringMakeThe seal ring is severely damaged. Subsequent operation of pitch bearingThis may cause deformation and tearing of the sealing ring, resulting in greaseA lot of leaks.

2 The internal structure design of the pitch bearing is unreasonable.

2.1 channel structure

Pitch bearing channel design affects grease in bearing internal groovesFluidity of the groove. Under normal circumstances,Add the pitch bearing from the grease hole.For lubricating grease injection, the pressure difference required for discharging waste grease from the grease drain hole is lessThe sealing ring can withstand the pressure value, while greater than the grease flowThe resistance value of the seal ring will not leak grease.. Required pressure differenceThe value is closely related to the resistance of grease flow, and small resistance requiresThe pressure difference is small, and the pressure difference required for large resistance is large. If changeThe internal channel design of the paddle bearing is unreasonable, and the grease flow resistance isLarge, not conducive to the uniform distribution of grease and internal pressure, greaseUnable to enter the fat drainage hole smoothly, resulting in poor fat drainage, resulting in sealingGrease overflow at the ring.

 

2.2 Lipid Pore Size and Distribution

Pitch bearingGrease Injection Hole and Grease Drainage HoleRequiredReasonable intervalClothTo ensure that the bearing can smoothly inject new grease and discharge waste grease. AdjacentThe distance between the fat injection hole and the fat discharge hole should be moderate. If the distance is too short, add fat.When the pressure of the grease injection hole is large and the pressure of the grease drainage hole is small, the newly added moistureGrease is easy to drain from the grease drain hole; if the distance is too long, the sealing ring will be used for greasing.The local pressure is large, which can easily lead to grease leakage. In addition, grease holeThe diameter of the section is too small, and the diameter of the mouth of the fat collecting bottle connected with the fat drainage holeIf it is too small, the spacing between the two adjacent grease holes on the bearing is too large, which will also increase the lubrication.Resistance to grease discharge, resulting in poor grease drainage, causing the internal pitch bearingExcessive pressure causes grease leakage.

 

3 improper selection of grease or improper setting of lubrication system

3.1 Improper selection of grease

 

The choice of grease is usually referredActual work of pitch bearingConditionAt the same time also need to considerConsistency of grease and type of additivesWait.The consistency of the grease is closely related to the ambient temperature.For every 5 ℃ decrease in degree, the consistency will increase by 1 times, and the grease will flow.If the consistency of the grease is not suitable or the compression resistance is notFoot, subsequent use is prone to curing phenomenon and block the grease system, guide.Causing grease can not be discharged normally and leakage from the sealing ring.

3.2 Grease Injection Quantity and Centralized Lubrication System Setting Unreasonable

The pitch bearing needs to be filled with a certain amount of grease before operation. The filling amount is about 60% ~ 80% of the internal space of the pitch bearing. Generally, the filling amount is about 70%. There are also individual pitch bearing suppliers who choose 80% of the filling amount in order to ensure sufficient lubrication.

 

Most wind turbines at home and abroad use centralized lubrication system for variablePaddle bearings are greased, and some wind turbine manufacturers are in-one.Step to reduce the maintenance cost of pitch bearings using manual regular filling lubrication.Grease. These two methods of lubricating grease filling are insufficient:PeopleThe amount of grease injected regularly and the grease injection cycle are often the same.test dataThere is a large deviation from the actual grease required for pitch bearings.Poor, the amount of grease injection is usually too much and uneven, which cannot be guaranteed.The lubrication time of the pitch bearing, plus the pitch bearing can beCan be filled with about 80% of the grease, easy to cause pitch bearing grooveLarge accumulation of local grease in the channel;centralized lubrication systemAdoptFromdynamic grease injectionway, so that the bearing lubrication is more adequate, although the guarantee ofThe lubrication time of the pitch bearing and the uniformity of the amount of grease injection, but in the variable.When the propeller bearing is not in operation or the machine is shut down for a long time, the centralized lubricationThe sliding system still continues to inject grease according to its preset fixed procedure, and the sameIt is easy to cause a large amount of local grease accumulation in the pitch bearing channel.

 

Under normal conditions, the sealing pressure of the pitch bearing seal ring is about2.8x10Pa, grease injection pressure required when pitch bearing is stationary and inoperativeThe force is about (2.5~2.8) x10Pa, required for pitch bearing operationGrease injection pressure is only 0.6 x10Around Pa. Due to the pitch bearingThe grease used is inherently less fluid, and the above 2 grease injection methodsThe large accumulation of grease caused by the formula will increase the pitch bearing channel.The pressure in the grease channel, thereby increasing the grease injection required during grease injectionPressure. When the grease injection pressure is greater than the sealing pressure of the pitch bearing seal ringforce, the grease will be removed from the pitch bearing under the action of the grease injection thrustLarge leakage at the sealing ring.

 

In addition, if the pressure pump or grease pipe of the centralized lubrication systemIf the air in the grease is not completely evacuated, the air will change with the grease.paddle bearing channel, resulting in excessive local pressure in the channel, when the pressureThe seal will open when the sealing pressure of the pitch bearing seal ring is greaterCircle, causing serious leakage of fat.

 

3.3 waste grease collection method is not appropriate

 

At present, the waste grease collection of wind turbine pitch bearing is widely used inSeveral waste grease discharge holes distributed on the bearing circumference are respectively installed and collectedWhen new grease is added to the grease bottle, the new grease takes the waste grease from the bearing cavity.Squeeze into the waste grease discharge hole, discharged into the grease bottle, need to be cleaned regularly.In fact, as the operating time of the pitch bearing increases, waste grease collectionThe effect is not good, easy fat leakage.