Humboldt HM-2315 Volume Change Apparatus - Manual (Page 2)

Introduction:
The Humboldt Mfg. Co. Volume Change Apparatus consists of a two chamber,
reversible piston assembly mounted onto an enclosure which contains the flow
control valves and internal fluid lines. The apparatus uses two different methods
for measuring the volume change. The standard 100 cc Volume Change
Apparatus is designed to utilize either a standard LSCT or a Humboldt Digital
Gauge for measuring the volume change.
The Volume Change Apparatus comprises a change over valve system, which
provides an unlimited capacity by reversing the flow. Once again an LSCT and
bracket or Digital Gauge must be used for measurement.
Installation:
Using 1/8 inch O/D tubing, attach a fluid line from the pressure system into the
left hand side (when viewed from the front) of the Volume Change Apparatus
(Figure 1). Note: The tubing is to connect into the same side as the Volume
Change/Bypass control valve. Using the same sized tubing, run a line from the
right hand side of the Volume Change Unit (i.e. from the Flow Up/Flow Down
valve side) to the backpressure valve situated on the Triaxial Cell base pedestal.
To measure the volume change, you need to fit an LSCT with bracket or Digital
Gauge to the top of the Volume Change Unit.
With the left hand valve set to VOLUME CHANGE position and the right hand
valve set to FLOW UP position, slowly fill the top chamber with de-aired water
with the top bleed valve open to release any entrapped air. Once the chamber
is full and all the air has been bled, tighten the air release valve at the top of
the chamber. To fill the bottom chamber repeat the above procedure with the
two chamber assembly rotated 180 Deg. (i.e. upside down) and the Right Hand
Valve to FLOW DOWN.
It is advisable to leave this apparatus for at least 8 hours with an internal
pressure of 700 kPa (102 psi) so that any remaining trapped air can be absorbed
into the water. It is then necessary to flush out the Volume Change unit with
fresh de-aired water. It may be necessary to carry out this procedure more than
once if there are any signs of air pockets in the system.
The Humboldt 100 ml Volume Change Apparatus can be used with a 25 mm
LSCT and bracket, or can be purchased complete with a Digital Gauge. These
units are usually supplied to connect to an existing laboratory set up where
there are sufficient change over valves and panels within the pressure system to
enable the reverse flow. Sometimes these units are used directly in the pressure
line by connecting the upper chamber to the base of the Triaxial Cell and the
lower chamber receives the de-aired water. In such case, it is necessary to apply
a pressure to the top of the chamber after each test to reverse the flow. This
pressure could be taken from the cell pressure line. Calibration and de-airing
etc. is carried out as mentioned earlier.