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Friday, 4 December 2015

HOW TO INSPECT A GEARBOX

We have seen "Classifications of gears” and "Gear terminology" in our previous post, where we have discussed the types of gears and various terms used in gear mechanism.

Now we will discuss here how to inspect a gearbox on site. In my previous post “Gearbox inspection procedure”, we have discussed each activity that we must have to follow before actual inspection of gearbox.

So, let us concentrate today, in continuation of previous post, with how to inspect a gearbox on site. We will see here the various important steps that should be followed to inspect a gearbox thoroughly on site.

Visual Inspection
Once gearbox and its surrounding area will be cleaned, we will have to inspect the following points of gearbox as mentioned below.
  1. Foundation fasteners condition of gearbox for checking tightness
  2. Gearbox’s cover fasteners condition for checking tightness
  3. Check any evidence of corrosion, overheating, oil leaks and damage.
  4. Oil leakage from input and output shaft
  5. Gearbox body for any cracks of welding or any damage of body of gearbox
Inspection for various evidences to ensure overheating of gearbox
During inspection of gearbox, we will check the shaft seals, air breathers to see any smoke. We will also spray the water over bearing housing or shaft to see whether water is evaporating, boiling or not. We will inspect the oil condition of gearbox by using dipstick or by looking over oil level indicator. If oil of gearbox is dark, it indicates that gearbox is overheating during operation.

Oil seal of input and output shaft
We will check the oil seal of input and output shaft for any oil leaks. If oil leaks observed from seals, it indicates that oil seal is damaged and we need to replace the oil seal on priority as damaged oil seal will allow to enter dust and water inside the gearbox and these dust and water will destroy the quality of gearbox oil and oil will not be able to perform its function as required.

 
Air breather condition
Next, we will check the condition of air breather and its filter, filter must be cleaned as it will allow exiting of vapor, which will be created during operation of gearbox, in environment. Air breather must be covered so that there will not be any possibilities of entering of any foreign particle, dust or water through air breather.

Oil level of gearbox
We will check the gearbox oil level by using dipstick or by observing the oil level indicator. If we observe oil level is low, we will have to plan to pour the oil of desired grade after completing the thorough inspection of gearbox.

Temperature measurement
We will check the temperature of gearbox body and we will also check the oil temperature during collection of oil sample with the help of infrared thermometer and we will have to record the temperature of oil and gearbox body to compare with operation and maintenance manual provided by the manufacturer of gearbox.

Measure shaft endplay and runout
We will check the shaft runout of gearbox with the help of dial indicator; we will also check any endplay in shaft. We will also check any relative motion between assemblies e.g. gear coupling and shaft or shaft and brake drum.

Inspection of internal components of gearbox
Now, we will have to check the gearbox internal components by opening the inspection ports. Before opening of inspection port, we must have to see the condition of all fasteners and seals of inspection cover or port. If there is any bolt damaged or missing, we need to use new bolt for properly covering of inspection port.
 Image courtesy: Google

Once we opened the inspection cover, we must have to take care to not pour any foreign particle in gearbox as if any foreign particles enter inside gearbox, it will damage the gearbox depending on type of foreign particle. 

Let us consider, we are opening the inspection cover and one bolt or nut, by mistake, entered inside gearbox. If we have observed this incidence, we will have to remove this foreign particle but it will take lot of time to remove as we will have to remove the top cover of gearbox to remove the foreign particle and it might be possible that we will have to replace the gearbox oil depending on the quality of gearbox oil. 

But suppose, if we have not observed the entry of bolt or nut inside the gearbox in this case, it will surely damage the gearbox internal components.

After opening the gearbox inspection cover, we will inspect the internal components of gearbox i.e. gears, shafts and bearings. If we are observing that bearings, gears or shafts are damaged slightly but we may continue with existing bearings, gears and shaft, in that case we will have to inform to our superior and management about the existing condition of internal components and we must have to keep mentioned internal components under observation.

 
Condition of gearbox oil
During inspection of gearbox internal component, we will have to take sample of gearbox oil and we will have to send the oil sample, by mentioning the gearbox name on sample bottle, in condition monitoring cell to analyze the quality of gearbox oil. 

Sound and vibration
We will observe the gearbox in operation for any abnormal sound and vibration. If there is any abnormal sound or vibration, we need to find out the location from where sound and vibration are coming.

Once we have completed through inspection of gearbox, we will record all detailed observations in our inspection form. Simultaneously we will present the inspection report to our superior to take necessary action wherever required.

Let us go ahead with our next article in engineering maintenance category.
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