There is not a lot of preventative maintenance to expansion joints and sleeves. All you can do is be sure they are installed correctly, that is, properly aligned. But they can be the cause of increased vibration levels and reduced flow problems. The key is to identify them as the cause.

The purpose of the flexible material connection is to isolate the blower from the building and its' piping system during operation by absorbing movement due to thermal growth and expansion. The Buna, or reinforced rubber, flex material is designed to withstand the heat, but it has a life span. Visual inspection for checks and cracking on the outside can be an easy indication of old age deterioration, but the inside can deteriorate much faster. Gas, moisture, and other contamination can severely weaken the interior surfaces, sometimes without any exterior wear.

The heat of operation can actually reduce, or eliminate any flexibility. This would increase the overall vibration, which in turn could increase bearing wear. If you find you are replacing bearings more frequently than you should be, take a closer look at the flexible isolation. Obviously, loose bolts and hose clamps can cause air leaking, but building foundations, concrete floors, and piping systems can also shift causing piping misalignment and added stress to the blower. I've seen plenty of piping support hangars pull out of the concrete ceilings, or support posts simply "loosen up".

Replacing expansion joints and pipe sleeves is relatively simple, just be sure to replace with the same type and size. However, if you have piping shifting that cannot be corrected, there are many types of "offset" couplings and sleeves that can be substituted instead. If the design application has changed, such as you are processing a different gas mixture, or the air temps are higher than original, you might want to review changing the design.

The first step in equipment preventative maintenance is identifying what can be done. Invest in PM, it will save you money!