Humboldt HM-2315 Volume Change Apparatus - Manual (Page 3)

Volume Change Measurement & Bypass
In order to measure the volume change, the left hand valve of the Volume
Change Apparatus must be set to VOLUME CHANGE position and the right
hand valve must be set to FLOW UP position or FLOW DOWN position.
During a test, water fills one of the chambers, while the other chamber is
opened and water drains out. As one chamber is filling and the other draining,
the piston will move inside the cylinder and the lever arm will move up or
down depending on which chamber is filling. The lever arm acts on the LSCT
or Digital Gauge which indicates the distance the piston has moved. This
information is then converted by the computer to volume change. During the
test, if the capacity of the sample exceeds the volume in one of the chambers,
it may be necessary to increase the volume change capacity. This is done by
reversing the flow direction. The flow direction is changed by switching the
FLOW UP/FLOW DOWN valve to the opposite direction. Note: When using
the reverse flow for greater capacity during a test, certain precautions should be
carried out when calibrating the apparatus (see calibration instructions).
By setting both valves to the BYPASS position, de-aired water can flow
through the change over valves system direct to the Triaxial cell. Volume is not
measured when the valves are in the Bypass position.
Calibration:
Switch on the power supply to the logger or monitoring readout unit with the
LSCT or Digital Gauge connected to it for at least one hour before attempting
calibration. Note: Some older monitors or loggers require a longer warm up
period. Please refer to your logger or read out unit guide.
With the probe of the transducer or Digital Gauge set to its maximum
downward position, set the monitor or logger to zero (if using a Digital Gauge,
set it to zero also). Note: The probe must still be in contact with the lever arm.
Adjust the right hand valve to the FLOW UP position until the maximum upward
movement has been achieved. Accurately measure the amount of water flowing
out with a measuring cylinder.
Alternatively you could work out the volume change by weighing the volume of
water displaced from the draining chamber. Weigh a beaker or other suitable
container with which to collect the water. Collect the water displaced when one
chamber is filled and the other drained. Weigh the beaker again with the water
displaced after the maximum upward movement has been achieved. Subtract
the empty container weight from the weight of the container and displaced
water. If the weight is measured in grams, this number will be the same as the
volume in millilitres or cubic centimetres.
Once the volume has been determined, the Digital Gauge should be set to
show the volume displaced and the logger or monitor should be adjusted to the
same volume.