Product Manual A

Maintenance
56 MTP4000-6000DZV/DZD Operating Manual 31609 A
3. Use new gaskets. In case of an emergency situation where you need to reuse the old gaskets, make sure
the gaskets are moist and flat.
4. Replace the impeller key and impeller. For solids handling pumps, install the impeller shims to maintain .030
inch minimum clearance between the backplate and impeller backvanes. Use the a long capscrew and sev-
eral washers to press on the impeller. Do not use the impeller lockscrew. The threads must be long enough
to enter the shaft approximately eight threads or turns by hand. This is necessary to protect the threads in
the shaft.
5. After replacing the impeller, remove the long capscrew and replace with the impeller lockscrew with the
impeller washer. The impeller lockscrew should always be new. Refer to table “Lockscrew Torque Values”
for torque requirements.
6. Replace the volute, sliding it carefully over the register. Bolt the volute to the backplate.
7. For seals, bring the gland and gasket against the face at the seal chamber and tighten the bolts evenly.
IMPELLER LOCKSCREW INSTALLATION
Impeller lockscrews are always right hand socket head capscrews. Stainless steel lockscrews are supplied with
Loctite 262, which should be applied to lockscrew threads and shaft prior to installation.
First determine the size and material of the lock, then torque to the appropriate value listed in the table below.
Lubrication
Do not lubricate the impeller lockscrew or tapped hole, between the lockscrew and impeller washer, or between the
impeller washer and impeller. Make sure parts are clean and dry; however, it is not necessary to remove the protective
coating from the screw. Lubricated bolts can be overstressed with the torques indicated.
DO NOT USE THE LOCKSCREW TO INSTALL THE IMPELLER.
CAUTION
Lockscrew failure can damage the impeller and volute. The impeller screw must be of the
best material, properly forged and machined to rigid specifications not available from local
suppliers. Purchase only lockscrews available from Generac Power Products to be sure of
quality.
Impeller Lockscrew Removal
1. Break the impeller lockscrew loose with a breaker bar.
Table 3 - Lockscrew Torque Values
Size
Torque for Stainless Steel Lockscrew (nonmagnetic)
302, 303, 304, 316 Series
.38- 6UNC 20 ft-lbs (27 Nm)
.50-13UNC 40 ft-lbs (54 Nm)
.62-UNC 90 ft-lbs (122 Nm)
.75-10UNC 135 ft-lbs (183 Nm)
1.00-8UNC 265 ft-lbs (359 Nm)
1.12-7UNC 360 ft-lbs (488 Nm)
1.25-7UNC 510 ft-lbs (691 Nm)
1.50-7UNC 875 ft-lbs (1186 Nm)