Dresser Roots DVJ WHISPAIR, Installation Operation & Maintenance

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  Dresser Roots

On a belt-drive unit with extended shaft, use spacer 
sleeve (62) to push inboard bearing (60) into its final 
position. There is no shaft shoulder behind this bearing, 
but there is a stop for the sleeve. Make sure that the 
inner race flange of bearing (60) is facing outboard.

2.  Install bearing lockwasher (25) and locknuts (24) on each 

shaft, and tighten nuts with a spanner wrench. Lock the 
nuts by bending a tab on each washer into a slot in the 
nut.

3.  Install new or original gears and set impellers as 

described in Operation B.

4.  Place bearing clamp plate (8) over main bearing (31) 

and tighten all screws. In the case of the extended type 
drive shaft, end cover (58) serves as the clamp plate but 
cannot be installed until later.

5.  Using 1/2” (13mm) feeler gauges, determine for each 

of the drive end bearings (31) the maximum clearance 
between the outer race and one of the rollers near the 
top. Obtain pieces of brass shim stock, of thicknesses 
corresponding to these clearances, about 3/4” (19mm) 
wide and long enough to reach completely through the 
bearings. Push one piece through each bearing, in the 
spaces between rollers, then rotate that shaft so that one 
roller of each row is up on the shim stock. This removes 
all clearances, and forces the bearing rollers and races to 
center as in normal running. Refer to Figure 14.

6.  Set the impellers lengthwise in the case by using long 

pieces of shim stock, or feelers, as wedges between the 
two ends of each impeller and the headplates. Using the 
total end clearance obtained in Step 8 of Operation D, 
the two ends of each impeller and the headplates. Using 
the total end clearance obtained in Step 8 of Operation 
D, place wedges equal to two-thirds of the total at the 
gear end and one-third at the drive or thrust end. It will 
be necessary to bump the shafts to obtain the required 
impeller positions. Set the drive end clearance first, after 
installing and tightening drive shaft end cover (58) if used.

7.  With feeler gauges, carefully measure the spaces 

between the drive end bearing carrier flanges and the 

headplate face. Insert shims (17) of correct thickness to 
fill these spaces. The original shims should be correct if 
bearings and carriers have been returned to the original 
location.

8.  Remove wedges from ends of impellers inside the casing.
9.  Tighten all bearing carrier flange screws.
10.  Recheck impeller end clearances for proper values 

per tables, then remove brass shim stock from both 
bearings (31).

11.  Check front and back clearances of impeller lobes as 

outlined in Operation C, and reset timing if not correct.

12.  Reassemble the unit, starting by installing the main end 

cover (5) and then proceeding in reverse order through 
Operation A from Step 5. Be careful with lip seal (23) or 
new O-ring (59) in end cover (5).

13.  Check the work area to make sure no parts have been 

left out in assembly.

14.  Turn the drive shaft over several times by hand as final 

check for impeller contact or case rubs.

15.  Reinstall coupling or belt sheave, check their alignment 

with driver and reconnect all external piping.

16.  Start and operate unit for a reasonable period in the 

manner outlined for initial starting. See OPERATION.

IMPELLER CLEARANCES

Instructions on impeller clearances under Operation C and 
Operation D do not include data on the amount of clearance 
to be expected. For blowers in good condition this informa-
tion is not essential in field service work. However, situations 
may arise where it is desirable to compare existing clearances 
with the correct values. Listed in Table 8 or 9 are the ranges 
of values used in original factory assembly. Clearances may 
change in service, but they should never be less than the 
minimum values listed. Only well 

qualified personnel

 should 

attempt to measure clearances for comparison with this data.

Figure 14