The piston tip should be checked for correct tolerances. (MI 0.3730
+/- 0.003 in.)
The guide bushing should be clean of material and easily slide up and
down the piston rod.
If running method B tests, are the factory supplied flags in good
condition.
The machine should be on a level surface. (Vertical alignment of the
bore)
The precision and accuracy of the test and instrument has been standardized by
ASTM D1238. Dynisco Polymer Test has found that the contributing factors to
the accuracy of the test includes sample weights (the amount of material tested),
timing (how long the material is in the heated barrel), packing technique,
dryness (has the material been properly dried), cleaning and cutting technique. It
is recommended to follow ASTM Specification D1238 for your material or
control sample. Also, pay attention to the recommendations of the manufacturer
or suppliers.
After a good cleaning and purge, your control sample should be run a
minimum of 5 times to verify that the problem is repeatable or even exists.
If you feel it is necessary to call the factory, please have your model number,
serial number and a complete program listing available (it may be helpful to fax
the program data) when you call.
Temperature is Unstable
Mercury Separation in Thermometer
Reuniting Mercury Thermometers
Unplug the unit and remove the front cover. Verify all cables and circuit cards
are properly connected.
While the cover is off and the unit is unplugged, clean out all debris from the
unit’s internal components with compressed air. Clean all debris from the units
cooling fan. Air must flow freely to properly cool the unit.
Before using any thermometer it should be examined very carefully for
mercury separation in the main mercury column, expansion chamber,
contraction chamber and bulb. Mercury separation in the bulb will usually
show as small bubbles. All the mercury must be united. If a thermometer does
not read zero at the ice point mercury separation is typically the cause.
There is no known method to completely insure that the mercury will
not separate in a thermometer when the thermometer is subjected to shock. This
can occur either in transit or by improper storage and handling. On the
following procedure describes a procedure for reuniting a separated mercury
column. Remember that the thermometer contains only two fluids, mercury and
gas. The object is to get all the liquid below the gas or conversely all the gas
above the liquid.
This method is the easiest to use and is the method PRINCO
recommends. In a small Dewar flask or thermos bottle mix powdered dry ice
with Methanol or Acetone. Holding the thermometer vertical, immerse about
3/4 of the lower section of the bulb into the mixture. DO NOT immerse the
capillary or funnel section that is above the bulb into the mixture. The main
portion of the mercury will retreat into the bulb, and the separated portion will
follow.
Occasionally the separated portion may cling to the walls of the funnel
portion of the bulb. When all the mercury, including the separated portion, has
retreated into the bulb, remove the thermometer from the dry ice mixture. (See
Figure 1). The mercury should go together. Stand the thermometer in a vertical
Series 4000 Melt Indexer Operation Manual Instrument Maintenance and Troubleshooting
66
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