After writing my last post regarding items overlooked on inspections, it occurred to me that there was an item that no one ever mentioned. Oil. I am not referring to the oil level. This is something that is rarely overlooked. I am talking about two factors: The type of oil that gets put into the gearboxes on overhead cranes, and the length of time that oil has been in the gear-case.
To keep your crane running efficiently you should be asking yourself these three questions regarding your crane’s oil….
- How do I know I have the right oil in my crane’s gear-case?
- What can happen to my crane if I have the wrong oil in my crane’s gear-case?
- Is the oil in my crane’s gear-case still good?
Time and time again I have seen 80/90 weight oil put into gear-cases regardless of what the manufacturer is recommending. 80/90 weight is not a “general lub all” lubricant. There is no such a thing. The confusion of what type of oil to put in a gear-case is caused by the misunderstanding of the oil weight and what it really means. Viscosity is the thickness of oil. The smaller the number the thinner the oil is. So the thicker it is the less resistant it is to flow. This is why it is so important to have the correct gear oil in your gear-box. Gear-case oil is thicker than your auto transmission oil to give it more protection and the resistant flow is not required to be as low as your car’s transmission. Gear-case oil typically will have additives as well. This will allow for extreme pressure, anti-wear, anti-rusting, demulsibility, or foam resistance. It is also important to know that gear oil is rated by the API (American Petroleum Institute), and motor oil is not, therefore are not comparable.
How do I know I have the right oil in my gear-case?
Depending on the gearing of your crane it is going to require a specific type of oil. Your crane has a recommended viscosity level of your oil to keep the gearing protected and cool. The type of oil is going to be dependent upon the operating temperature of the gears, the gear speeds, the gear-box pressure, loads, containability , and the type of gearing. Your crane’s owner’s manual should tell you what the required oil is for the gear-boxes. Do not assume that every gear-box on your crane takes the same oil either. This is typically not the case. The hoist gear-box will more than likely take different oil than the bridge gear-case. If you are unsure of the oil type than contact your overhead crane service company and they should be able to provide you with the appropriate type. If the crane’s manufacturer cannot be found and not enough information can be provided to the service company to get the recommended oil then you will need to read the AGMA (American GearManufacturers Association) standard specifications and get an appropriate viscosity level for your gear-box. It is important to note as well that the manufacturers requirement for gear-case oil is specified based on a normal ambient temperature, and operating conditions. If the crane is being used outside these parameters it is possible that you do not have the correct oil even though you are using what is specified for your crane. If this is the case, you will then have to refer back to AGMA standards and pick the most suitable oil grade for your crane.
What happens if you have the wrong oil in your gear-case?
Depending on the oil viscosity is too high or too low you could have several different problems. Both can cause overheating which is the number one sign of the wrong oil. You can also get foaming of the oil that can also cause major oil leaks and severe damage to various components. Excessive noise from the gear-case could also be from the wrong lubrication. During a routine inspection, the overhead crane inspector will check for adequate oil level, and will inspect the gear-case breather. The breather is important because the oil will expand and constrict with the operating temperature. If the breather is clogged, it can blow out the seals on the gear-case. A preventive maintenance program on your overhead cranes can help prevent contamination accumulating in your gear-case. Oil samples on an annual basis is also help see the quality of your oil without the high cost of a gear-case inspection.
Is the oil in my gear-case still good?
The average shelf life of oil is about 5 years, some oil manufacturers state that their oil is only good for as little as two years. Just because you have oil right out of the barrel, it does not mean that it is good oil. Ask your overhead crane service provider how they store their oil. If they have no method of rotating its stock, or knowing what the shelf life is then you may want to consider who you have servicing your crane. The average recommended gear-case inspection is recommended every four years. If you haven’t had your gear-case inspected then now is a good time to get it scheduled. The gear-case inspection is very important because not only does it get fresh oil in the gear-case, your internal components will be inspected. It is the only way of knowing if you have any wear. This is where your load brake is on most hoists so it is a vital inspection. If you are changing the oil yourself you should do it when the oil is warm. The gear-case should also be flushed out with flushing oil. When you add the recommended oil you should keep the drain plug off. If the gear-case is running loud, you may have the wrong type of oil or contaminated lubricant. Contaminated lubricant is typically caused by water or dirt getting into the gear-case causing corrosion, and foaming which will deteriorate the oil. This will restrict the amount of oil to the gears and cause gar and bearing wear. Water can get into a gear-case simply through condensation, or moisture. Other issues could be gear and bearing wear or failure. This is where an annual oil sample will be able to tell if any contaminates are present in the gear-case. These tests also check for metal fragments so you can tell if you are getting wear on your gearing.
No two oils are the same and just because you have the correct oil in your gear-case it does not mean it is still good if it has been in that gear-case for years. The correct fresh oil is vital to preventing wear on your crane’s gearing, clutches, and load brakes. Take annual samples of the gear-case to inspect for wear, and contamination. Conduct periodic gear-case inspections (typically every 4 years) according to the manufacturer’s recommendation. A preventive maintenance program on your overhead cranes will add a longer life to your equipment and keep them running safe.