Flowserve LPNV Worthington - Manual (Page 37)

LPNV USER INSTRUCTIONS ENGLISH 87900031 – 06/14
Page 37 of 48
6.9 Reassembly
To reassemble the pump consult the sectional
drawings, see section 8, parts list and drawings.
Ensure threads, gasket and O-ring mating faces are
clean.
6.9.1 Wear rings
The impeller is fitted with both front and rear wear
rings.
The impeller rings are renewable and should be
replaced when badly grooved, and/or when pump
performance does not meet the system
requirements. Whenever it becomes necessary to
replace either wear ring, both rings involved
(impeller and casing cover) must be ordered and
replaced as a set as they are furnished standard
size only. Spare impeller wear rings are supplied
with a material stock over outside diameter which
has to be machined off after rings fitting on impeller.
If an impeller with its wear rings is ordered as spare,
it will be supplied
fully machined, including wear
rings outside diameter, to original dimensions.
Casing wear rings are always supplied fully
machined. Be sure to re-establish the original
running clearance between the two wear rings
involved by machining the fitted impeller rings.
6.9.1.1 Impeller wear rings
a) To remove impeller wear rings, mutually remove
wear ring set screws or ground off tack weld.
Rings can be machined off or grind two slots
diametrically opposite across the width of the
ring so it can be split apart. Use caution if ring is
removed by grinding so as not to damage
impeller hubs.
IMPELLER
HAND
GRINDER
IMPELLER
RING
Figure 6.3
b) To fit new weaqr rings:
Make sure ring fits on impeller are free of nicks
or burrs. Heat new ring to 107 °C (225 °F) and
install on impeller. Drill and tap new holes in
impeller spaced half the circular distance from
the previously used holes in the impeller. See
sketch below.
Figure 6.4
Impeller wear rings when installed must
be machined to establish original diameter and
running clearance. Whenever an impeller has
new wear rings fitted it must be dynamically
balanced before being reassembled. Refer to the
Cross Sectional drawing for the requested
running clearance.
The impeller wear ring bore is relieved
at one edge. Ensure that the ring is installed on
the impeller so that the chamfered edge is sitting
against the impeller.
Do not tighten set screws
excessively, as this will distort the wearing ring.
Lock set screws by prick punching.
6.9.1.2 Casing wear rings
Each wear ring is locked against rotation with a
cylindrical pin.
a) To remove the wear ring, press it out. If this
method does not easily effect removal of the
ring, it can be split apart. First, however, drill one
or more holes in the face of the worn ring.
b) New rings to be installed must be shrunk by
freezing -20°C (-4°F) when installing in casing
cover. Fit and secure with a locking pin.
Replacement wear rings are furnished standard
size in the bore. Check the running clearance
between impeller and casing ring against the
appropriate value.