ProMinent DULCOMETER PH-501 Assembly And Operating Instructions Manual page 869

If reusing the timing gears, the gears should be returned to their original positions.
A. Obtain 2 gear locking assemblies. Clean the inside and outside diameters of both locking assemblies.
Clean the inside diameter of 2 gears. Clean the outside diameter of the both rotor shafts. Lightly oil the
surfaces that have been cleaned. Note: DO NOT USE MOLYBDENUM DISULFIDE, MOLYKOTOE, OR
ANY OTHER SIMILAR LUBRICANTS.
B. Slide a locking assembly into a gear. Install the gear and locking ring assembly onto the idler rotor shaft.
Push the locking assembly firmly until flush with the end of the idler rotor shaft and hand tighten the 7 cap
screws. Align and adjust the connections.
C. Use a torque wrench to tighten the screws to 75 in. lbs. in a diametrically opposite sequence. Ensure that
none of the screws will turn when 75 in. lbs. is applied to them a second time.
D. Tighten the screws further to 150 in. lbs. in a diametrically opposite sequence. Ensure that none of the
screws will turn when 150 in. lbs. is applied to them a second time.
E. Slide the second locking assembly into a gear. Install the gear and locking ring assembly onto the drive
rotor shaft. Note the circular mark on each gear indicates the position of the largest runout. These marks
must be 180 degrees apart when the gears are installed.
F. Push the locking assembly firmly until flush with the end of drive rotor shaft and hand tighten all cap
screws but leave them loose enough that the gear can be rotated on the shaft.
G. The first step in setting the interlobe clearance is to measure the total clearance between two meshing
lobes. This is accomplished by determining the maximum feeler gauge thickness that will fit between the
rotor lobes near the pitch diameter. The clearance should be measured along the entire length of the
meshing lobes. This measurement should be taken for each of the 2 interlobe meshes. The location of
the smallest total interlobe clearance should be marked on the rotor lobes. Refer to diagram in
FIGURE 7-4, page 33. Use feeler gauges to check clearances between impeller lobes at positions
A—A and C—C. Add the clearances, and divide the total clearance evenly between A—A and C—C.
H. Rotate the rotors until the two lobes that have the smallest total interlobe clearance (as determined in
step G) are visible through the discharge port. Lock the idler rotor from turning by wedging a shop rag
between the tip of a lobe and the air cylinder. Insert feeler gauges with a thickness equal to the half
clearance (determined in step G) between the drive rotor and the idler rotor lobe. Pull the drive rotor tight
against the feeler gauges (drive rotor, feeler gauges, and idler rotor must be tight against each other).
While holding the drive rotor tight against the feeler gages rotate (in the direction that the rotor turns) the
gear on the drive rotor until a tooth on it contacts a tooth on the gear on the idler rotor. Hand tighten the 7
capscrews in the drive gear locking assembly. Align and adjust the connection.
I. Use a torque wrench to tighten the screws to 75 in. lbs in a diametrically opposite sequence. Ensure that
none of the screws will turn when 75 in. lbs is applied to them a second time.
J. Tighten the screws further to 150 in. lbs in a diametrically opposite sequence. Ensure that none of the
screws will turn when 150 in. lbs is applied to them a second time.
K. Check gear backlash four places at 90 degree intervals as described in the disassembly procedure
(Item 4).
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