Chain conveyor troubleshoot guide

 

Sl No.	Problems	Potential Cause	Solution
1	Chain rises off from sprocket	1. Excess chain slack.	1. Adjust the amount of slack equally at both sides.
		2. Excess wear at the bases of sprocket teeth.	2.Carryout hard facing of the sprockets
		3. Excess chain extension.	3. Replace the elongated chain parts.
		4. Foreign material stuck to the bases of sprocket teeth.	4. Remove the foreign material from the bases of the teeth.
		5.Reverse rotation of conveyor	5.Avoid reverse rotation of the conveyor when chain tightened is uneven
		6.Uneven chain tightening of chain
2	Chain separates poorly from the sprocket.	1. Sprocket misalignment.	1-Adjust alignment.
		2. Excess chain slack.	2-Adjust the amount of slack.
		3. Excess wear at the bases of sprocket teeth.	3-Avoid uneven tightening of the chain
		4.Uneven chain tightening of chain
3	Wear to sides of link plats and sprockets	1-Sprocket misalignment.	1-Adjust alignment.
		2-Trough width is lesser than required	2-Increase trough & runner flat width as per site conditions & links assembled width
		3-Chain runner flats size is less
4	Poor chain flexure	1-Inadequate oiling/lubrication	1-Lubricate properly, use standard lubricant during chain assy.
		2-Foreign materials between pins and bushes.	2-Wash the chain to remove foreign materials, and then oil it.
		3-Corrosion between bushes.	3-Replace with an environment resistant chain series.
5	Abnormal noise	1-Chain is too tight or too loose.	1-Adjust the chain slack.
		2-Inadequate oiling.	2-Lubricate properly.
		3-Excess wear of sprockets and chain.	3-Replace chain and sprockets or get worn-out area filled & hard face it
		4-Sprocket misalignment.	4-Eliminate contact with the case.
		5-Slats touching the trough
6	Chain vibration	1-Excess chain slack.	1-Adjust slack.
		2-Excess load vibration.	2-Reduce load variation
		3-Excess chain speed leading to pulsation.	3-Use guide stoppers to stop chain swaying.
		4-Chain flexes poorly at some points.	4-Replace the more worn-out chain parts during overall maintenance
		Sprocket wear.
		5-Worn out or more clearances in rollers & bushes
7	Damage to pins, bushes, rollers.	1-Inadequate oiling.	1-Lubricate properly.
		2-Jamed foreign bodies.	2-Remove foreign bodies.
	Deformation of link plate holes.	3-Corroded components.	3-Review chain and sprocket selections.
		4-Use with greater than allowable load.	4-Eliminate the abnormal load, and review chain and sprocket selections
		5-Abnormal load action.
8	Chain link cut or pins cut	1-Overload operation	1-Ensure all over load, ZSS protections are working
		2-Low breaking load of chain	2-Select chain with higher breaking load if this problem persists

Points to be kept in mind

1-Never weld the heat treated chains, as heat effect can reduce the strength & cause chain to break

2-Never go for electroplating of heat treated chain links, as it causes the hydrogen embrittlement failure

3-Do not use new chain on worn out sprockets

4-Gradual elongation of chain above 3%  in total chain length, indicates that the chain will soon jump the sprockets

Read SOP Coal handling & DE system

Comparison between Acetylene & LPG fuels for gas cutting operation

 

SL No.	Acetylene	LPG (Propane)
1	Highest flame temperature up to 3100 Deg C	Flame temperature up to 2800 Deg C
2	Flame speed up to 7.5 m/sec	Flame speed up to 3.3 m/sec
3	Most of the heat released is in inner cone	Most of the heat released is in outer cone
4	Higher flame GCV of inner cone (4500 kcal/M3)	Lower flame GCV of inner cone (2500 kcal/M3) as compared to acetylene
5	Stoichiometric air fuel ratio1.2:1 (Requires 2.5 to 3 Oxygen cylinders for burning one Acetylene cylinder)	Stoichiometric  air fuel ratio 4.3:1 (Requires 7 to 8 Oxygen cylinders for burning one LPG cylinder)
6	Can be used in gas welding, as acetylene when burning with air creates reducing zone that cleans the steel surface	Cannot be used in gas welding as it does not create reducing zone
7	Acetylene has Specific gravity 0.9 kg/m3, so if it leaks it will raise in air without harming much	Propane has Specific gravity 1.6 kg/m3, which is heavier than air. So if it leaks it will concentrate in deck level or any other closed/corner area
8	Acetylene requires less air for complete combustion	Propane requires more air for complete combustion, so there may be chances of formation of carbon monoxide (CO) in case of incomplete combustion. This incomplete combustion may result into poisoning of working area, as CO is poisonous gas
9	Can be used for cutting & welding applications in industry	Used only for domestic applications

Why do Bearings fail?

 Following are the 16- top listed reasons for bearing failure or damages

1-Lubrication:

Following are the 7 major reasons for bearing failures related to lubrication

1-Lack of lubrication

2-Less lubrication

3-Over lubrication

4-Contaminants in lubricants

5-Wrong method of lubrication

6-Poor quality of lubricants

7-Selection of wrong lubrication

8-Lubricant failure

2-Bearing clearance:

Bearings may fail if the clearance between rolling elements & race is too less & too more. Lesser bearings clearance than desired creates friction & temperature rise.

More bearing clearance creates vibrations

3-Operating the bearings at higher vibrations for long time:

Bearings can operate satisfactory at the vibrations range up to 5 mm/sec, vibrations more than this reduces the bearing life & eventually failure.

Operation range: 0.5 to 3 mm/sec

Alarm Range: 3 to 5mm/sec

Trip range: > 5mm/sec

High vibrations in machine or bearings are due to;

1-Axial vibrations due to misalignment

2-Horizontal vibrations due to imbalance in machine

3-Vertical vibrations are due to looseness in foundation bolts

4-Shaft run out

4-Operating the bearing at excessive loads:

Excessive load on bearings leads to premature fatigue, over loading creates other side problems like bearing overheating, damage to rolling elements.

Brinelling occurs when loads exceed the elastic limit of the ring material. Brinell marks show as indentations in the raceways which increase bearing vibration (noise]. Severe brinell marks can cause premature fatigue failure.

 

5-Overheating

Overheating & damage of the bearings is due to;

1-Lack of lubrication

2-Over lubrication

3-Improper cooling of bearings

4-Excessive loads

6-Smaller clearance between rolling elements & race

Operating the boilers at higher temperature (>90 deg C for ball bearings & sump cooling) will lead to annealing the races & rolling elements that, eventually fails the bearings.

7-Miss alignment

Running the equipments at misaligned condition creates vibrations & excessive loads on bearings in axial, vertical & horizontal directions that causes bearing failures.

Misalignment also leads into failure of couplings & equipments parts like seals, impellers, pulley etc

8-Frequent start & stops of machine

Leads to jerk load on bearings & leading to reduction of its life

9-Not following of equipment/machine SOP:

If machine SOP (standard operating procedure) is being not followed, then it could cause not only bearing failure but also machine other elements.

For example if pump is not started with discharge valve closed or not stopped without closing discharge valves, it could cause jerk loads on bearings & impellers. After some cycle it will reflect it effect on misalignment, vibrations etc

10-Reverse rotation of machine or reverse loading of bearing element:

Some machines & bearings are not recommended for reverse rotation.

For example: Boiler feed pumps & screw compressors are meant to rotate in only one direction

Also Angular contact ball bearings are meant to take load only in one direction

11-Corrosion in Bearings:

Red brown areas on balls, raceways, cages, or bands of ball bearings are symptoms of corrosion. This condition results from exposing the bearings to corrosive fluids or a corrosive atmosphere. The usual result is increased vibration followed by wear, with subsequent increase in radial clearance or loss of preload. In extreme cases. Corrosion can initiate early fatigue failures.

12-Loose & tight fittings of bearings:

Fitting of bearings loose on shaft or loose in housing leads to rotation of bearings outer race in housing, this causes rubbing & bearing damage.

As like loose fitting, very tight fit can also cause excessive load on rolling elements which eventually creates overheating & vibrations

13-Entry of water in bearings grease

14-Material or manufacturing defects in bearings cause bearing failure as soon as it is been installed.

15-Leakage current in VFD motor bearings lead to bearing failure

16-Carrying out welding near bearings or Plummer blocks without proper earthing can lead to flow of currents through bearings, which ultimately causes bearing failure

CHAIN CONVEYOR MAINTENANCE GUIDE

Read Powerplantandcalculations.com

Questions & answers on bearings