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

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GEA19684  ISRB_2008 rev._11.15

It is possible for a base-mounted assembly to become 
twisted during shipment, thus disturbing the original align-
ment. For this reason, make the following checks after the 
base has been leveled and bolted down. Disconnect the drive 
and rotate the unit shaft by hand. It should turn freely at all 
points. Loosen the unit foot hold-down screws and determine 
whether all feet are evenly in contact with the base. If not, 
insert shims as required and again check for free impeller rota-
tion. Finally, if unit is direct coupled to the driver, check shaft 
and coupling alignment carefully and make any necessary 
corrections.

In planning the installation, and before setting the unit, 
consider how piping arrangements are dictated by the unit 
design and assembly. Drive shaft rotation must be established 
accordingly and is indicated by an arrow near the shaft.

Typical arrangement on vertical units has the drive shaft at the 
top with counterclockwise rotation and discharge to the left. 
Horizontal units are typically arranged with the drive shaft at 
the left with counterclockwise rotation and discharge down. 
See Figure 4 for other various unit arrangements and possible 
conversions.

When a unit is DIRECT COUPLED to its driver, the driver 
RPM must be selected or governed so as not to exceed the 
maximum speed rating of the unit. Refer to Table 1, page 13 
for allowable speeds of various unit sizes. 

A flexible type coupling should always be used to connect the 
driver and unit shafts.

When direct coupling a motor or engine to a blower you must 
ensure there is sufficient gap between the coupling halves and 
the element to prevent thrust loading the blower bearings. 
When a motor, engine or blower is operated the shafts may 
expand axially. If the coupling is installed in such a manner 
that there is not enough room for expansion the blower shaft 
can be forced back into the blower and cause the impeller 
to contact the gear end headplate resulting in damage to the 
blower. The two shafts must be in as near perfect alignment 
in all directions as possible, and the gap must be established 
with the motor armature on its electrical center if end-play ex-
ists. Coupling manufacturer’s recommendations for maximum 
misalignment, although acceptable for the coupling, are 
normally too large to achieve smooth operation and maximum 
life of the blower.

The following requirements of a good installation are 
recommended. When selecting a coupling to be fitted to the 
blower shaft Roots recommends a taper lock style coupling 
to ensure proper contact with the blower shaft. Coupling 
halves must be fitted to the two shafts with a line to line thru 
.001” interference fit. Coupling halves must be warmed up 
per coupling manufacturer’s recommendations. Maximum 
deviation in offset alignment of the shafts should not exceed 
.005” (.13 mm) total indicator reading, taken on the two 
coupling hubs. Maximum deviation from parallel of the inside 
coupling faces should not exceed .001” (.03 mm) when 
checked at six points around the coupling.

When a unit is BELT DRIVEN, the proper selection of sheave 
diameters will result in the required unit speed. When selecting 
a sheave to be fitted to the blower shaft Roots recommends 
a taper lock style sheave to insure proper contact with the 
blower shaft. This flexibility can lead to operating temperature 

problems caused by unit speed being too low. Make sure 
the drive speed selected is within the allowable range for the 
specific unit size, as specified under Table 1, page 13.

Belt drive arrangements should employ two or more V-belts 
running in grooved sheaves. Installation of the driver is less 
critical than for direct coupling, but its shaft must be level and 
parallel with the unit shaft. 

The driver should be mounted 

on the inlet side of a vertical unit (horizontal piping) and 
on the side nearest to the shaft on a horizontal unit.

 The 

driver must also be mounted on an adjustable base to permit 
installing, adjusting and removing the V-belts. To position the 
driver correctly, both sheaves need to be mounted on their 
shafts and the nominal shaft center distance known for the 
belt lengths to be used.

CAUTION:

 Drive couplings and sheaves (pulleys) should have 

an interference fit to the shaft of the blower (set screw types 
of attachment generally do not provide reliable service.) It is 
recommended that the drive coupling or sheave used have a 
taper lock style bushing which is properly sized to provide the 
correct interference fit required. Drive couplings, that require 
heating to fit on the blower shaft, should be installed per 
coupling manufacturer recommendations. A drive coupling or 
sheave should not be forced on to the shaft of the blower as 
this could affect internal clearances resulting in damage to the 
blower. 

Engine drive applications often require special con-
sideration to drive coupling selection to avoid harm-
ful torsional vibrations. These vibrations may lead to 
blower damage if not dampened adequately. It is often 
necessary to install a fly-wheel and/or a torsionally soft 
elastic element coupling based on the Engine manufac-
turer recommendations.

The driver sheave should also be mounted as close to its 
bearing as possible, and again should fit the shaft correctly. 
Position the driver on its adjustable base so that 2/3 of the 
total movement is available in the direction away from the unit, 
and mount the assembly so that the face of the sheave is 
accurately in line with the unit sheave. This position minimizes 
belt wear, and allows sufficient adjustment for both installing 
and tightening the belts. After belts are installed, adjust their 
tension in accordance with the manufacturer’s instructions. 
However, only enough tension should be applied to prevent 
slippage when the unit is operating under load. Excessive 
tightening can lead to early bearing concerns or shaft break-
age.

Before operating the drive under power to check initial belt 
tension, first remove covers from the unit connections. Make 
sure the interior is still clean, then rotate the shaft by hand. 
Place a coarse screen over the inlet connection to prevent 
anything being drawn into the unit while it is operating, and 
avoid standing in line with the discharge opening. Put oil in the 
sumps per instructions under 

LUBRICATION

.

Piping

Before connecting piping, remove any remaining anti-rust 
compound from Unit connections. Clean pipe should be no 
smaller than unit connections. In addition, make sure it is 
free of  scale, cuttings, weld beads, or foreign material of any 
kind. To further guard against damage to the unit, especially 
when an inlet filter is not used, install a substantial screen 

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15/02/2016   11:17:05