Hale MG - Manual (Page 56)

Muscle Pumps
3-13
In clear water, the clearance rings continue to
effectively seal for hundreds of hours of pumping.
In dirty or sandy water, the impeller hub and
clearance rings will wear faster than in clear water.
The more the wear, the greater the bypass and the
lower pump performance. Also, the greater the
pressure at which each stage is operated, the larger
will be the bypass and the more the performance
will be lowered.
When new, the radial clearance between the
impeller hubs and the clearance ring is from 0.005
to 0.007 inch per side. Any increase will allow
more bypass and result in lower performance. But
when the pump is adequately powered, it should
not be necessary to replace clearance rings and
impellers until the average radial clearance reaches
0.015 to 0.020 inch or more per side, as measured
by a feeler gauge.
Often, replacement of the clearance rings is all that
is necessary. This will largely reduce the bypass
and restore the pump to near original performance.
A complete restoration requires that oversize
clearance rings be installed and the impeller turned
or the impeller may also be replaced.
Anode Check
The zinc anodes should be inspected every 12
months. Replace when over 75% of the zinc has
been consumed (Refer to figure 6-15 for original
dimensions). Performance of the anode life will
vary with water quality and pH. Anodes conform
to MIL Spec A180001.
TRV Test
The TRV should be tested every 12 months. The
following procedure should be used to test the
TRV. Before testing, make sure a clear view is
available to the TRV discharge.
DO NOT RUN PUMP FOR LONGER THAN IS
SHOWN IN THE TABLE, AS OVERHEATING
COULD OCCUR AND SERIOUS DAMAGE TO
PUMP WILL RESULT.
1. Close all discharge valves including pump and
engine coolers so there is no flow through the
pump.
2. Use care that engine does not overheat, set the
pump discharge pressure to one of the
pressures listed.
Time in Minutes
PRESSURE TRV120
TRVM120
TRV170
TRVM170
200 PSIG (13.8 Bar) 10 20
400 PSIG (27.6 Bar) 4 8
600 PSIG (41.4 Bar) 2 4
3. The thermal relief valve should discharge
water through the 1/8 NPT or metric discharge
line approximately within the time specified.
4. The table is for midship type pumps. The
thermal relief valve will open faster on smaller
pumps, dependent on how close it is to the
impeller.
5. The table is based on 70°F (21°C) water and
70°F (21°C) air temperature. The thermal
relief valve will open faster in hotter
conditions and slower in cooler conditions.
6. Units equipped with TRV-L kit will flow up to
1-2 GPM (3-7 LPM) of water before lamp turns
on.
If unit fails to open in time allotted, remove TRV
in accordance with Procedures in Section 5.
Place TRV-120 on work area with inlet facing up.
Pour water of 120°-130°F (66° to 72°C) into opening
of TRV. Element should open allowing water to flow
out, if valve does not open replace valve. For TRV-
170, use water at 170
o to 180 o (77 o to 82 o C).
Refer to figure 3-2 for a service chart including
recommended service points and intervals.