Dresser Roots DVJ WHISPAIR, Installation Operation & Maintenance

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  Dresser Roots

Lubrication

A - SEPARATE OPPOSITE GEAR END RESERVOIRS

A simple and reliable splash lubrication system is employed in 
ROOTS

®

 blowers. All friction parts - gears, bearings and shaft 

seals - are lubricated either by dipping directly into oil reser-
voirs or by receiving splash oil from other rotating parts. All 
reservoirs require the same grade of oil as specified in Table 
3 for various ambient temperature ranges at the installation 
site. Reference to the appropriate assembly drawing, Figure 
15, will assist in understanding of the following discussion.

At the opposite gear end of the blower, the upper (or driven) 
shaft bearing is lubricated from its own oil reservoir, formed 
by the bearing carrier (6) and the deep blind end cover (5A). 
At a normal oil level, bearing rollers dip into the oil as they 
roll through the bottom of their raceway. The oil picked up 
is carried over the top by bearing rotation, and some of it 
transfers to the shaft behind the bearing to lubricate the 
dynamic lip-type inboard seal (27). A slight amount of oil may 
work through this seal, but it will be thrown off by the shaft 
slinger, and further prevented from reaching the air chamber 
by a labyrinth type seal where the shaft passes through the 
headpiece. The chamber between the two sealing points 
is vented to atmosphere and serves not only to drain any 
seal leakage but also to keep the lubrication system at 
atmospheric pressure.

At the lower (driving) shaft the arrangement is the same as 
described above when a short shaft for direct coupling is 
provided. Here an outboard shaft seal (23) is provided in 
the end cover (5). On V-belt driven blowers the drive shaft 
and bearing carrier (63) are extended and provided with and 
additional inboard bearing (60). This creates a larger reservoir 
requiring about three times as much oil to fill.  Lubrication is 
the same as for the shorter shaft, except that two protruding 
screws (96) are provided to insure adequate splash oil for 
bearing (60).
At the gear end of the blower the bearings, seals and timing 
gears are enclosed by a gearbox containing a double 
(primary and secondary) oil sump arrangement. In a vertical 
style blower the secondary sump is formed of sheet steel 
and contoured around the bottom half of the lower gear. It is 
fed with oil at a controlled rate from the surrounding primary 
sump in the gearbox itself, through a metering orifice in the 
secondary wall. The lower gear teeth pick up oil and carry 
it to the meshing point with the upper gear, from where it is 
splashed onto oil control shields with leaders that direct the 
oil to the two bearings. A dam at each bearing maintains 
the desired oil level there, with excess overflowing into the 
gearbox primary sump. Inboard sealing of the shafts is the 
same as at the drive end. In a horizontal style blower the 
gear end lubrication arrangement is identical, except that a 
secondary sump is formed around each gear and the total oil 
capacity is more than doubled.

Note

 - A good grade of industrial type non-detergent, 

anti-foaming oil should be used when the average of blower 
inlet and discharge temperature is 125°F (52°C) or lower. 
Oil should be changed after the first 100 hours of operation. 
After initial oil change, normal oil change periods under these 
conditions may be considered as 2000 operating hours. 

Table 3 - Recommended Lubrication Oils

Ambient 

Temperature

Viscosity Range, SSu at 

100% °F (83 °C)

Above 90 °F (32°C)

1000-1200

32° to 90°F (0°-32°C)

700-1000

0° to 32°F (-18°- 0°C)

500-700

Below 0°F (-18°C)

300-500

During initial operation, install a temporary corrosion resistant 
screen at the compressor inlet connection. Screen should be 
made of 16 mesh (.020” diameter) wire backed with 2 mesh 
wire cloth. Backing cloth-wire diameter shall be a minimum 
of 0.063” diameter for 12” pipe, 0.080” diameter for 16” pipe, 
0.105” diameter for 20” pipe, and 0.120” diameter for 24” 
pipe. For 30” and 36” pipe use 1 mesh backing cloth with a 
minimum of .180” wire diameter for 36” pipe. The table below 
gives approximate screen pressure drop. A manometer 
connected to read pressure drop across the screen will 
indicate when it needs cleaning. Do not allow pressure drop 
to exceed 55 inches H2O. Clean and replace the screen 
until debris no longer appears. Do not leave it installed 
permanently, as the wire will eventually deteriorate and pieces 
may go into the blower causing serious damage. (Typically, 
screens are installed 1-2 days of operation.)
Discharge piping requires a pressure relief valve, and should 
also include a suitable pressure gauge and a manually 
operated unloading valve. The latter permits starting under 
no-load conditions. The optional back pressure regulator 

shown in figure 5 will be required if volume demands vary 
while blower operates at constant speed. It may be vented 
if only air is being handled. A vent silencer may be required, 
depending on permissible sound levels in the general 
surroundings.
In some installations, particularly where two or more blowers 
discharge into a common header, it is recommended that a 
direct acting or free swinging check valve be provided in each 
discharge line. These valves, properly installed protect against 
damage resulting from reverse rotation caused by back flow 
through an idle blower.
In making pipe connections to the blower, use special care 
in lining up the mating flanges. They must contact squarely 
and accurately, without imposing strain on the blower casing. 
Any attempt to draw flanges together by force will probably 
distort the blower and cause internal contacts. Also, the 
blower should not carry more than the weight of one pipe 
fitting at each connection. After bolting up the flanges, rotate 
the drive shaft by hand to check for rubbing contacts caused 
by strains or dirt.