Dynamax HPFM3, Installation And Operation Manual, Page: 36 / 86

Revision: JUNE 2017 36
3. Under low pressure, and using a towel to catch water drops, disconnect the water inlet tube (INLET) from the water inlet
on the 8-way manifold. Then allow air and water to escape from the upper half of the filter and PVC tubing. You may
need to tilt the HPFM so the water filter outlet is higher than the rest of the system. After all air and bubbles have escaped and
only water flows out, replace the inlet hose and tighten the inlet coupling on the 8WI. Water should stop dribbling, once the 8WI
coupling is tight.
4. Attach a clear outlet tube to the 8WO, and open the outlet valve. Then, open the flow inlet valve, the brown capillary valves, to
allow any large air bubbles in the manifolds to escape. Once you observe the tube is clear of bubbles, open each capillary in
turn, to remove bubbles. Proceed to 5.5.2 for more steps to clear the manifolds.
5.5.2 Removing Air Trapped in the 8-way Manifold
Small air bubbles trapped in the 8-way manifolds or in the outlet tubing can seriously degrade the performance of the HPFM
during transient measurements of hydraulic conductance (Tyree et al. 1995). Air bubbles can be detected by doing a transient
conductance measurement with a solid metal plug mounted in the compression fitting. See the instructions under Section
5.6 , “
Transient Measurement of Conductance
”, to see how to perform a transient conductance measurement.
Air bubbles cause errors mostly when measuring low conductance by the transient method when using the lowest
three flow ranges, i.e., the Green , Orange and Red ranges. The best way to remove air bubbles from the 8-Way valves is
to perfuse water through the system overnight (12 hours) after bleeding the manifold. Steps for perfusing the water can be
found in Subsection 5.4.2 , “
Priming a totally Empty Captive Air Tank (CAT)
.”
The steps for bleeding the manifold are:
a. Open or make sure to open the Water Supply Valve to the “flow” position (right).
b. Make sure that you still have pressure by checking the pressure gage.
c. Open the flow inlet valve. Keep all other valves closed.
d. Loosen connector for PT1 and PT2, allowing a small amount of water to flow out.
e. Close the Water Supply valve removing the pressure from the connection.
Each HPFM is shipped with a 5’ (1.5 m) length of Red tubing about 0.005” ID. Connect the 1.5 m Red tube to the outlet tube
using the smallest “Omnifit” connector part. Pressurize the CAT to about 350 – 480 kPa (50-70 PSI) and open all valves on
both 8-way connectors. Allow degassed water from the CAT to flow through the system for 8-16 hours. Less than 0.5 liters
of water will pass through the HPFM overnight, but that flow is usually sufficient to dissolve all air bubbles trapped in the
8-way valves and the outlet tube. In some rare cases, an air bubble may be trapped in PT2 between the 8WO and PT2. Air
must be removed by carefully disconnecting Blue caps from the 8WO and injecting water using a 7/8” hypodermic needle
and syringe.
Short Needle Injection Demonstration
7/8" Needle
Pressure Transducer
3cc Syringe