Howden Roots Metric Series, Installation, Operation And Maintenance Manual

ISRB_2002 GEA 19171 Roots URAI 

Page 12 of 32

Inspection & Maintenance: Roots Universal RAI 

series blowers 

A good program of consistent inspection and 

maintenance is the most reliable method of minimizing 

repairs to a blower. A simple record of services and 

dates will help keep this work on a regular schedule. 

Basic service needs are: 



 Lubrication 



  Checking for hot spots 



  Checking for increases or changes in vibration and 

noise 



  Recording of operating pressures and temperatures 

Above all, a blower must be operated within its specified 

rating limits, to obtain satisfactory service life. 
A newly installed blower should be checked often during 

the first month of full-time operation. Attention thereafter 

may be less frequent assuming satisfactory 

performance. Lubrication is normally the most important 

consideration and weekly checks of lubricant levels in 

the gearbox and bearing reservoirs should be 

customary. Complete oil change schedules are 

discussed under 

LUBRICATION.

Driver lubrication practices should be in accordance with 

the manufacturer’s instructions. If direct connected to 

the blower through a lubricated type coupling, the 

coupling should be checked and greased each time 

blower oil is changed. This will help reduce wear and 

prevent unnecessary vibration. In a belted drive system, 

check belt tension periodically and inspect for frayed or 

cracked belts. 
In a new, and properly installed, unit there is no contact 

between the two impellers, or between the impellers and 

cylinder or headplates. Wear is confined to the bearings 

(which support and locate the shafts) the oil seals, and 

the timing gears. All are lubricated and wear should be 

minimal if clean oil of the correct grade is always used. 

Seals are subject to deterioration as well as wear, and 

may require replacement at varying periods. 
Shaft bearings are designed for optimum life under 

average conditions with proper lubrication and are 

critical to the service life of the blower. Gradual bearing 

wear may allow a shaft position to change slightly, until 

rubbing develops between impeller and casing. This will 

cause spot heating, which can be detected by observing 

these surfaces. Sudden bearing failure is usually more 

serious. Since the shaft and impeller are no longer 

supported and properly located, extensive general 

damage to the blower casing and gears is likely to 

occur. 

 
Oil seals should be considered expendable items, to be 

replaced whenever drainage from the headplate vent 

cavity becomes excessive or when the blower is 

disassembled for any reason. Some oil seal leakage 

may occur since an oil film under the lip is required for 

proper operation. Periodically leaked oil should be wiped 

off from surfaces. Minor seal leakage should not be 

considered as indicating seal replacement.  
Timing gear wear, when correct lubrication is 

maintained, should be negligible. Gear teeth are cut to 

provide the correct amount of backlash, and gears 

correctly mounted on the shafts will accommodate a 

normal amount of tooth wear without permitting contact 

between lobes of the two impellers. However, too high 

an oil level will cause churning and excessive heating. 

This is indicated by unusually high temperature at the 

bottom of the gear housing. Consequent heating of the 

gears will result in loss of tooth-clearance, backlash and 

rapid wear of the gear teeth usually will develop. 

Continuation of this tooth wear will eventually produce 

impeller contacts (knocking), and from this point serious 

damage will be unavoidable if blower operation is 

continued. A similar situation can be produced suddenly 

by gear tooth fracture, which is usually brought on by 

sustained overloading or momentary shock loads. 
Problems may also develop from causes other than 

internal parts failure. Operating clearances within a 

blower are only a few thousandths of an inch. This 

makes it possible for impeller interference or casing rubs 

to result from shifts in the blower mounting or from 

changes in piping support. If this type of trouble is 

experienced, and the blower is found to be clean, try 

removing mounting strains. Loosen blower mounting 

bolts and reset the levelling and drive alignment. Then 

tighten mounting again, and make sure that all piping 

meets blower connections accurately and squarely 

Foreign materials in the blower will also cause trouble, 

which can only be cured by disconnecting the piping and 

thoroughly cleaning the blower interior. 
A wide range of causes and solutions for operating 

troubles are covered in the 

TROUBLE SHOOTING 

CHECKLIST.

The remedies suggested should be 

performed by qualified mechanics with a good 

background. Major repairs generally are to be 

considered beyond the scope of maintenance, and 

should be referred to an authorized Howden Roots 

distributor. 
Warranty failures should not be repaired at all, unless 

specific approval has been obtained through Howden 

Roots before starting work. Unauthorized disassembly 

within the warranty period may void the warranty.

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17/09/2015   12:52