Quantcast Excessive sediment

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TM 5-684/NAVFAC MO-200/AFJMAN 32-1082
the spacers function to prevent adjacent cells from
tect this action. Cells which do not gas during
knocking together. The side rails are covered by a
charge may indicate problems such as undercharge,
corrosion-resistant cover (such as a plastic channel)
short circuits in the cell, or impurities in the elec-
where they touch the jars. Check to ensure that all
trolyte.
side rails, end rails, and spacers are in place, and
c. Mossing. Mossing of lead-acid cells is caused by
that bolts are properly torqued. Portions of the rack
overcharging, or charging at excessively high rates.
seismic equipment may occasionally be disas-
The manufacturer may provide moss shield protec-
sembled to allow maintenance to be performed on
tion on the top of the plates for some cell construc-
the battery or for cell replacement. The ability of
tions. Mossing results from the accumulation of a
the rack to protect the battery during an earth-
sponge-like material on top of the negative plates or
quake will be impaired if rack reassembly is not
straps. The material is shed predominantly from
properly tightened.
the positive plates and is carried off by gassing. If
(3) Grounding. Check that ground connections
deposited on the positive plates, gassing simply
washes it off again, but the material will adhere if
are correct, tight, and uncorroded.
deposited on the negative plates. Over time, the
f. Damaging actions to be noted. Low electrolyte
negative plates build up a sufficient deposit to
levels, vibration, hydration, or frozen electrolyte can
bridge and make contact with positive plates, caus-
often damage batteries beyond repairability and
ing partial shorts. If mossing is found during an
such batteries should be noted for prompt replace-
inspection, expect to find excessive sediment as
ment.
well.
g. Low electrolyte levels. Water should be added to
d. Sediment. Observing quantity and color of
cells when inspection reveals electrolyte levels be-
sediment in clear lead-acid battery jars also indi-
low the high level line. The manufacturer should be
cates the battery's condition.
consulted immediately about cells where the elec-
(1) Excessive sediment. Excessive sediment
trolyte level is below the plate tops. Water should
usually indicates overcharge or charge at exces-
not be added to these cells until the manufacturer
sively high rates. The sediment from a well main-
has agreed that this is the proper action or has
tained cell may look like a layer of dust on the
inspected the cells and recommended filling. Elec-
bottom of the jar. The sediment from a poorly main-
trolyte levels below the plate tops can cause perma-
--
tained cell may completely fill the space provided
nent cell damage, and the cell may need to be re-
under the plates and resemble hills. Partial short
placed. A record of the amount of water added to
circuits will occur when the sediment hills reach the
each cell should be kept and checked with the bat-
plate bottoms.
tery manufacturer's normal cell water consumption
(2) Color of sediment. Dark or chocolate brown
requirement. Lead-antimony batteries normally ex-
sediment hills beneath the positive plates indicates
perience an increase in water consumption with
continuous overcharge. Gray sediment in hills be-
age. Water consumption in excess of the manufac-
neath the negative plates indicates continuous un-
turer's requirement is an indication of overcharg-
dercharge. Excessive but somewhat mixed sediment
ing. A cell that has been recently moved or trans-
hills, showing both positive and negative materials,
ported should not have water added until it has
indicate the battery has probably undergone ran-
been placed back on charge for the period of time
dom periods of undercharge and overcharge. Where
recommended by the manufacturer. If the plates
excessive sediment is noted, examine cells for moss-
were exposed while moving cells, consult the manu-
ing.
facturer for recommended action. Vibration during
e. Battery racks. Battery racks should be checked
movement will tend to free hydrogen bubbles at-
tached to the plates. The loss of these bubbles will
during visual inspections. Included are checks for
cause a decrease in the electrolye level. Once the
structural integrity, corrosion, and proper ground-
cell is installed, the bubbles will reappear, and the
ing.
electrolyte level will increase. Never add acid (or
(1) Corrosion.  The jars normally rest on
alkali) to a cell, nor any additive which claims to
corrosion-resistant supports or  plastic jar-
rejuvenate cells.
supporting channels installed on the rack structure.
Check these and all items composing the rack for
(1) Vibration. Check the surface of the electro-
corrosion.
lyte for indication of any battery vibration. Battery
life will be reduced in proportion to the length of
(2) Seismic. If the battery rack is a seismic type
time and action of any severe systematic vibration.
for installations requiring earthquake protection,
Excess sediment, when there is no apparent reason
additional checks of the rails and spacers must be
for that sediment (the battery has not experienced
made. Seismic racks use rails and spacers to pre-
overcharging or undercharging), can indicate recur-
vent movement of cells during an earthquake, and
14-5





 


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