Discussion on changing technology of large slewing bearing of bucket turbine

Bucket turbine is the main equipment of the coal conveying system, and the  operation status of bucket turbine directly affects the load of the  unit.Large slewing bearing is an important part of bucket turbine rotary  mechanism. After the slewing bearing is damaged, how to replace it safely  and with high quality in a short time is the main purpose of this paper.  This paper analyses the cause of damage of large slewing bearing and  introduces emphatically the technology of "jacking method" to replace large  slewing bearing of bucket turbine. This method is used to replace the big  bearing of DQL1200/1600-30 type bucket turbine of shentou NO.2 power plant.  The practice proves that this method is successful. The construction period  is only 6 days and the cost is 100,000 yuan. More than 1 year of operation  after replacement, stable rotation, good meshing of big and small gears,  normal operation and rated output.

The reasons for turbine large slewing bearing damage are as follows:
(1) Big bearing has been in service for 12 years, with a long cycle.  Defects were exposed as early as 2001 when it was overhauled.

What are the selection tips for slewing ring bearings?

In the mechanical industry, slewing bearing has been widely used, because the development of slewing ring, varieties are increasing, and how to choose the slewing bearing using in machinery, we must have some understanding.Let me follow FRB Bearings staff to learn about some of the slewing bearing selection techniques.

Bearing type selection
Bearing type is generally chosen by the user's technical personnel according to the use conditions of the supporting products and the bearing load.The sales mainly know whether the actual load of the user is consistent with the selected bearing. If the bearing fails to meet the use demands, the customer should be advised to change the model as soon as possible.

8 points for illustrating what need to notice when using slewing bearing?

If we know what to do with something, we can use it better and extend its life.The same is true of the slewing bearing, we only know what to pay attention to during the use of the bearing, to avoid, to run it better.So, what do you pay attention to when using slewing bearing?Here are eight points to illustrate:

1. Slewing bearing is coated with a small amount of NO. 2 or NO. 3 lithium grease in the raceway when it is manufactured, and the user should refill the new grease according to different working conditions.

2. During the operation of the slewing bearing, lubricant grease should be regularly added. Generally, ball slewing bearing should be lubricated once every 100 hours, and roller slewing bearing should be lubricated once every 50 hours.Special working environment, such as high temperature, humidity, dust, temperature changes and continuous work, should shorten the lubrication cycle.When filling grease, slowly rotate the slewing ring to make the grease fill evenly.

3 factors let you know which factors affect the slewing bearing service life?

The main factors influencing the slewing bearing service life are structural design, manufacturing process and materials.

First of all, the slewing bearing structure design is reasonable, so that the swing bearing has a good life.slewing bearing is after forging, heat treatment, turning, grinding and assembly, and other processes.The rationality, progressiveness and stability of each machining process also affect the slewing bearing life.

What's the application and selction of swing bearing?

Slewing bearings has a unique bearing capacity and is usually used on lifting machines, excavators, rotary tables, wind turbines, telescopes and tank turrets. With the improvement of machining methods and the update of design concept, today's slewing bearings can be applied to smaller, more complex and more sophisticated applications.

In the machine tool industry, the slewing bearings of standard structure is applied with high precision grade and preload to eliminate gap and reduce vibration. The radial runout of the slewing ring and the diameter tolerance range from one thousandth to one thousandth of an inch (2. 54 tan), compact structure, small section size, and the diameter range can be as small as 50 mm(this type of slewing supported steel ball size is smaller than the traditional heavy series slewing bearings steel ball size). This prompted the designers to reconsider the traditional slewing ring configuration.

How to judge if the bearing can be used again?

"Inspect the bearings that have been removed from the equipment during regular maintenance, operation inspection and peripheral parts replacement to determine whether they can be used again or whether the condition is better than bad.The bearing and appearance of the disassembled bearing should be carefully investigated and recorded."

Secondly, check if the raceway surface, rolling surface and mating surface, as well as the wearing state of the cage are damaged or abnormal.

To determine whether the bearing can be used again, it shall be decided after considering the degree of bearing damage, machine performance, importance, operating conditions, inspection period, etc.Check the results, if the bearing has damage and abnormal conditions, the contents of the damage section to find out the cause and develop countermeasures.In addition, the inspection result shows that if there are the following defects, the bearing can not be used again, and a new bearing needs to be replaced.

4 factors for influence slewing bearing capacity

Slewing ring failure form has two kinds, one is the raceway damage, the  second is broken teeth, and the raceway damage accounted for the proportion  of over 98%, so FRB Bearings said, the raceway quality is the core of the  quality of slewing bearing, there are many factors influencing the quality  of the slewing ring raceway.Among them, the raceway hardnesss, raceway  hardener depth,raceway radius of curvatureand and aceway contact angle are  undoubtedly the most important four influencing factors.They affect the  quality of the raceway in different ways and determine the bearing capacity  and service life of the slewing bearings.

Raceway hardness
The hardening hardness of the slewing bearing raceway has a great impact on  its rated static capacity. The minimum hardness specified in the standard  is HRC55, and the actual average quenching hardness is usually around  HRC57. Therefore, the actual bearing capacity of most of the slewing  bearing is higher than the theoretical value calculated according to  HRC55.When the hardness is lower than HRC53, even if the safety factor of  1.2 is left, it is not safe to use. In particular, when the hardness is  only HRC50, the safety factor of 1.7 is useless, which is very  dangerous.Lack of hardness can easily cause the failure of slewing bearing,  from the beginning of the pitting on the surface of the raceway to the end  of collapse.

What are the used screws requirements in building mechanical slewing bearings?

It is well known that slewing bearings are used in many fields and are also  one of the most important construction machinery parts.To ensure the safe  operation of slewing ring, the whole process of production and installation  of slewing bearings is often involved.FRB Bearings will introduce what are  the used screws requirements in building mechanical slewing bearings?, come  together to understand!

1. Requirements for bolts used:
The size of bolts used shall conform to the regulations of GB/ T5782-2000  and GB/ T5783-2000, and the strength grade shall not be lower than the 8.8  level specified in GB/ T3098.1-2000, and the proper strength grade shall be  selected according to the bearing capacity.So make sure you choose the  right bolt.That's how it works.

2. Operating standard of nuts:
The size of nuts shall comply with the provisions of GB/ T6170-2000 and GB/  T6175-2000, and their mechanical properties shall comply with the  provisions of GB/ T3098.2-2000.Therefore, the standard of nut use is also  very strict, which should be noted.

How is the slewing bearing sealed at high temperature?

Slewing bearing is an important part of mechanical equipment, which is not only used in engineering machinery, but also widely used in port, military, wharf and other fields.But now many friends are asking about the slewing bearing at high temperature if the bearing is sealed.Here, FRB BEARINGS are simple to talk about.

The slewing bearing is mainly composed of upper ring, lower ring and a full complement ball.These two single row and double row designs, as well as the convenience of pre-drilled mounting holes.In real life, some bearings are only tightened at the fixed blade end, some are tightened at both the fixed blade end and the moving blade end, the way of tightening is cylinder type, there are also institutional linkage.Under the working environment of heavy load and low speed, the bearing is sealed by rubber sealing ring or labyrinth seal.

4 main advantages of slewing drive,FRB Bearings let you know!

FRB Bearings slewing drive with advanced processing and manufacturing and  assembly process, not only ensure the security, stability and reliability  of the gear reducer and protective but also has beautiful appearance.FRB  Bearings slewing drive four advantages.

1. High integrability of slewing drive
The slewing drive is highly integrated, and the maximum and minimum slewing  bearings reducer can drive the parts and the load difference is dozens of  times, but their sizes, specially the axial size of the transmission chain,  have little difference. This advantage is conducive to the flattening of  the structural form of the series drive connection parts, so as to reduce  the whole mechanical equipment.

What's the selection principle of slewing bearing steel?

When designing and manufacturing rolling bearings, What's the selection  principle of slewing bearing steel?The following principles are generally  followed to select bearing materials.

1. According to bearing working conditions
1) Operating temperature: bearings working at normal temperature, using  chrome bearing steel.Working temperature higher than 150 ℃ lower than 250  ℃ using chromium bearing steel, but with special heat treatment (200 ℃ or  300 ℃ tempering required).

2) Size of impact load: bearing under strong impact load, generally not  using chrome bearing steel, most of the high quality carburized structural  steel, impact tool steel or tempered structural steel.

3) Contact media: bearings used in corrosive media must be made of  corrosion-resistant steel or alloy steel with good corrosion  resistance.Structural steel, shock resistant tool steel or tempered  structural steel.

What's the matter need to notice before the slewing bearing installation?

Turntable bearing usually consists of four parts: inner ring, outer ring, roller, spacer, etc.Because the core component adopts slewing bearings, it can bear axial force and radial force at the same time.It has many forms, but its structure is basically the same.Swing bearing is widely used in life, it is an indispensable part in people's life. So, what's the matter need to notice before the slewing bearing installation?Learn from FRB BEARINGS.

Before installing slewing ring bearings, you need to know the following methods: