Howden Roots Tri-RAM 409, Installation, Operation & Maintenance Manual

GEA19684  ISRB_2008 rev._11.15

10

Inspection & Maintenance

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 there after 
may be less frequent assuming satisfactory performance. 
Lubrication is normally the most important consideration and 
weekly checks of lubricant levels in the gearbox and bear-
ing 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 and wear, and may require replace-
ment at varying periods.

Piston ring seals (28) are designed to operate without rub-
bing contact, once temperature and thermal growth have 
stabilized. The stationary rings will rub the rotating sleeve 
(38) briefly as a result of temperature cycles that occur 
during the startup and shutdown of the unit. The sleeves are 
hardened and the rings are coated with dry lubricant that 
provides for temporary break in wear. Replace piston ring 
seals if they become excessively worn.

Shaft bearings are designed for optimum life under aver-
age 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. Sud-
den 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. Periodi-
cally leaked oil should be wiped off from surfaces. Minor 
seal weepage 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 de-
velop. 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 overload-
ing 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 interferences 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 leveling and drive alignment. 
Then tighten mounting again, and make sure that all piping 
meets blower connections accurately and squarely Foreign 
materials sucked into 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 & 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 your authorized Roots distributor.

Warranty failures should not be repaired at all, unless spe-
cific approval has been obtained through a Sales Office or 
the factory before starting work. Unauthorized disassembly 
within the warranty period may void the warranty.

GEA19684_ISRB-2008_Tri-RAM_rev02.16.indd   10

15/02/2016   11:17:05