Flushing Gearbox Sumps

If they are flushing the sumps in the shop or during a shut down period I see no real problem. But, if they are replacing the oil with the flushing fluid or adding it in the field and operating the machinery under load then you may be doing much more damage than is gained by removing contaminants that are aleady attached to the surfaces of the machinery. Solvents greatly thin out your oil and reduce or even elliminate the protective oil film that prevents metal to metal contact (wear), and can be very difficult to remove causing low viscosity problems after the solvent is removed and replaced with oil often requiring several oil changes to get back to normal viscosity. The contaminants which are suspended in the oil contribute most to wear and are easily removed using a portable filter cart. Clean oil will act as a solvent to some extent to lift sludge and other deposits that have attached to the surfaces of your machinery which then can be removed by the portable filter cart. Dirt and metal particles that have settled out of the oil and are on the bottom of the sump are not much of a concern to the long term life as they are not circulating in the fluid. I would recommend modifying your equipment to be able to easily attach a portable filter cart and periodic filtering as indicated by oil analysis. If you have larger systems fit them with an ofline filter to continuously clean the fluid and you will be amazed at how clean your sumps stay.

I agree with BuckHntr, offline filtration is the way to go if possible.

If you have to flush try using a low viscosity oil of the same type as your currently using e.g if your using Mobilgear 632, try flushing using a Mobilgear 626. Compatibility shouln't be an issue this way, be aware that your next oil sample may have a lower viscosity than usual bacause of resdiual left in the gearbox.

I'm unfamiliar with the solvent you mentioned, but the solvents I know of generally are defatting in nature. I suspect this maybe detrimental to seals?