When someone asks for pricing on a replacement blower, the first question we have to ask is-what is the application?  There are standard air blowers used in "Wastewater" treatment plants that simply draw in ambient filtered air and send it to water tank diffusers.  Usually nothing special here.  Then there are "Industrial" applications, which could be a myriad of various type of design needs: from chemical tank agitation & fluidized bed incineration to filter backwash systems and pneumatic conveying.  Central "Vacuum" systems for factories, schools, and similar applications could be considered part of the industrial apps.  Finally, "Landfill Gas" applications, which is truly a vacuum system, requires a much different blower than the simple aeration machine. 

The first major difference is the gas blower must be certified spark free!  Landfill gas is much more volatile than ambient air.  The gas is also much more corrosive.  A regular air blower would not last much more than one year in a LFG application.  It would corrode and seize up.  The gas machine must also be leak free.  The sealing between the cast iron sections must be absolute.  The gas must be contained in the blower with special bearing housings and shaft seals.  Sometimes they are built with stainless steel shafts, and special drive end seal packing glands.

Internally, there are many different types & grades of protective coatings used to prevent corrosion of both the cast iron, and sometimes the aluminum, or fabricated, impellers. If coatings are used on the impellers, oftentimes the impellers must be "trimmed" down to allow the addition of the coating, or the cast iron sections must be "opened" up to provide the correct clearances for design performance.  The coatings: such as epoxy, ceramic, or baked enamel, are chosen by the design engineer based on the properties of the gas mixture being drawn through the blower. 

As far as operation, the bearings are usually the same, so the maintenance is no different.  The gas, with it's inevitable mixture of water, is always detrimental to the operation.  The gas blowers probably have an expected life of half that of air blowers-5 years vs. 10 years.  However, there are many exceptions to this rule.  I've seen LFG blowers fail after only 4 months of operation, and there are some out there still running for over 12 years now. 

A good water separator, and regular preventative maintenance, are the keys to extending the life of landfill gas blowers.  Invest in PM, it can save you money!    

Temperature alarms in motor windings--a Case History.