"We have many pumping units for our artificial lift operations. The new units sold do not have breathers on the gearbox. They breathe though the seals on the gearbox shaft, but this allows for contamination of the oil. These gearboxes are slow rotating, high torque, thus gear wear is expected and accelerated if the oil is contaminated. Other than adding a desiccant breather, what modifications/upgrades could be made to minimize oil contamination?"
The units that I believe you are referring to are the gearboxes on outdoor "pumpjacks" used in crude oil production, but the problem could occur in any outdoor gearbox. They are remote units with a large static sump and no filtration.
Particle and water (condensation) contamination are real issues with these units. Your idea of a desiccant breather is my first choice. We need to clean and dry the air going into the gearbox so we need to force the air through the breather, rather than allowing it to pass through the seal.
Would a bearing isolator labyrinth seal fit onto these units? It provides a more torturous path for the air to pass through the seal, which would knock out more contaminants and also force more of the air through the desiccant breather.
Another separate issue is selecting an oil that has the proper viscosity characteristics for these units; one that is thin enough in winter to flow to the bearings and yet thick enough in summer to lubricate the gears. I have always been a proponent of using a synthetic ISO 150, EP gear oil, depending upon your geographic location. Viscosity Index Improver additive shearing is a serious issue with these heavily loaded gears.
Bob Scott, Noria Corporation
Submit a question | Discuss on Message Boards | 
