Goulds Pumps 3420 - IOM - Manual (Page 59)

INSPECTION AND OVERHAUL
The model 3420 parts must be inspected to the following
criteria before they are reassembled to ensure the pump will
run properly. Any part not meeting the required criteria
should be replaced.
GENERAL
Clean all parts before assembly. This is especially
important at all O-ring grooves, threads, and bearing areas.
Remove any burrs. Replace all o-rings. Inspect labyrinth
seals for rubbing and wear. Replace as required. Replace
all lip (grease) seals. Inspect the oil rings. Replace if worn
excessively. Inspect and replace as necessary the
mechanical seal and/or its components per the
manufacturer’s instructions.
CASING
The casing (100) should be inspected for excessive wear or
pitting, particularly at the cutwater areas. It should be
repaired or replaced if the wear or pitting exceeds 1/8 in
depth. The parting gasket surfaces on both the upper and
lower halves should be cleaned and inspected for any
irregularities.
PARTING GASKET
Inspect the parting flange gaskets (351S and 351D) and
replace if torn or otherwise damaged. The recommended
gasket materials are Garlock Blue Gard 3000™ or
Armstrong N8090. See Table 8 for the correct gasket
thickness. Use the upper half casing as a template. Strike
the sheet with a soft face hammer. This will cut the gasket
against the edge of the casing.
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CAUTION
Take care not to chip any internal coatings that may
have been applied to the casing’s internal passages. If
the casing has an internal coating, it may be easier to
cut the gasket using a knife.
The gasket must cover the entire surface of the parting
flange. Pay special attention to the areas around the wear
ring locks.
NOTE: If the area around the wear ring locks are not
properly sealed, leakage will occur from the high to the
low pressure zones in the pump. This will result in lost
performance and efficiency.
For pumps with mechanical seals, cut the gasket
approximately ¼ in (6.35 mm) long at the face of the
stuffing box. This excess then should be trimmed to a
perfect fit after the pump casing is assembled.
NOTE: SX and MX pump parting flange gaskets are
supplied with pre-cut outer edges and fastener holes.
IMPELLER
Inspect the impeller (101) and replace if there is excessive
wear due to erosion or corrosion, particularly at the leading
and trailing edges of the impeller vanes. If the impeller
needs to be trimmed, it should be balanced to the tolerances
in Table 7. Determine whether a single plane or a two
plane spin balance is required by calculating the diameter to
width ratio of the trimmed impeller. Imbalance can be
corrected by grinding on the outside of the shrouds near the
impeller periphery. The impeller bore diameter should be
measured to ensure a proper fit on the shaft. Refer to Table
8 for the correct tolerances. Contact your Goulds
representative for special requirements on Lo-Pulse
impellers or rotating elements.
3420 IOM 8/09
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