Hello everyone, I would like to address the issues we are experiencing with the Agitator Gear Box failures at our PVC plant. We have a total of 8 poly gear boxes in place, which are designed as speed reducing gear boxes with a combination of helical and bevel gears. Gear reduction occurs in 3 stages - starting with the input shaft equipped with helical gears, followed by the intermediate shaft, and finally the output shaft with spiral bevel gears. The main challenges we are encountering are: 1) Excessive Radial and Axial Floats of the input shaft 2) Regular occurrences of gear failures such as tooth failures, Pitting, and scoring in gears. 3) High levels of moisture content in the oil. We are particularly interested in understanding why there are high radial and axial floats in the input shaft (operating at 1500 RPM) despite maintaining proper alignment. What could be the potential causes for these issues? Thank you, Jatan Desai
When it comes to gearbox design, the type of bearings used plays a crucial role. Angular contact rolling element bearings are typically found in this type of gearbox. Improperly set bearings can lead to both radial and axial movement, with radial movement being particularly damaging and resulting in gear failure. For instance, if one rotor's bearing is loosened, the gears may no longer be parallel, leading to excessive loading on the teeth and potential damage such as pitting or scoring. Moisture content in the oil of gearboxes can be caused by various factors. One common cause is air being drawn in through a breather when the gearbox is hot and then cools down, causing condensation inside. Using synthetic lubricants can help mitigate this issue. It is recommended to have experienced individuals rebuild the gearboxes, paying close attention to bearing settings, as it requires skill. Consider switching to synthetic lubricants for better performance and longevity.
Hello John, Thank you for your thoughtful response. I want to confirm that we do indeed utilize Taper Roller Bearings for this particular service. Your suggestion will definitely be taken into consideration. Feel free to share any other recommendations you may have. Best regards, Jatan Desai
When discussing a PVC agitator, it appears that the equipment configuration includes a vessel where the process takes place, and agitation is achieved through a rotor powered by a gearbox with spiral bevel on the output shaft. The speed is then reduced by the intermediate and input shaft of helical gear type. A motor drives the gearbox, which is mounted on a plate adapted to the gearbox casing, with the assembly suspended at the bottom. One issue with this setup is the resonance frequency, which can be influenced by the vessel's level and the properties of the process.
quote: This discussion is about the issues we are facing with the Agitator Gear Boxes at our PVC plant. We have 8 poly gear boxes in place, which are designed for speed reduction using a helical/bevel gear setup. The gear reduction process involves three steps - helical gears on the input shaft, an intermediate shaft, and spiral bevel gears on the output shaft. Our current problems include: 1) Excessive radial and axial floats on the input shaft 2) Regular gear failures such as tooth damage, pitting, and scoring 3) Presence of high moisture levels in the oil. We are seeking insights into the causes of the high radial and axial floats on the input shaft despite proper alignment measures. Any suggestions or advice would be greatly appreciated. Thank you.
Hi Jatan, the issues you've described sounds like they could be connected. If the input shaft is experiencing excessive radial and axial floats, it can closely impact the alignment of the gears leading to tooth failures, pitting and scoring. These failures could potentially be caused by excessive loading or perhaps a misalignment in your shaft. As for the moisture content in the oil, usually, these are due to leaks or condensation if the gearbox is exposed to fluctuating temperature conditions. An inadequate sealing system might allow moisture to seep in as well. When moisture mixes with the lubricant, it reduces its effectiveness, potentially exposing gears to quicker wear and tear. It might be worthwhile checking your loading conditions, alignment, sealing process, and oil grades. Remember, regular and thorough maintenance can go a long way in protecting your gearboxes.
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Answer: 1. What are some common challenges faced in agitator gear box failures at PVC plants? - Common challenges include excessive radial and axial floats of the input shaft, regular occurrences of gear failures such as tooth failures, pitting, and scoring in gears, and high levels of moisture content in the oil.
Answer: - The gear reduction process in poly gear boxes at PVC plants occurs in 3 stages: starting with the input shaft equipped with helical gears, followed by the intermediate shaft, and finally the output shaft with spiral bevel gears.
Answer: - The high radial and axial floats in the input shaft of agitator gear boxes could be caused by various factors such as misalignment issues, wear and tear of components, or potential lubrication problems.
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