Tech Talk; Air
By Mark Greves (June Beach Water Association)
This new column will be devoted to educating our membership through
brief discussions revolving around system piping and operations.
We will attempt to highlight specific products and applications in the
hope of sharing the wealth of knowledge within WIWSA and from outside
professionals in the industry. As a way of beginning this
discussion we will use the alphabet as a guide, so our first discussion
will begin with the letter A; for Air.
You may ask; what the heck does Air have to do with our Water delivery
system. The answer is a lot. It can be your friend, as in a
“Hydro-Pneumatic” tank, a pressurized tank system to push the water out
for delivery at an acceptable pressure. Or it can be your enemy if
that air pressure in your tank exceeds the “MAWP” (Maximum Allowable
Working Pressure) of your tank or if it becomes entrapped in a control
valve or pump. For this discussion we will focus on the later
part, the potential for problems associated with air “entrapped” in your
delivery system. Air Release valves are often installed at high
points in the piping system, but they don’t catch everything.
When you start up a new system, replace equipment or open your system to
“atmosphere” for any reason, air will enter the piping and will need to
be evacuated. “Bleeding” entrapped air out at the highest points
commonly does this. The high point is where Air will naturally collect
due to elevation or the shape of equipment or the piping design.
In most cases the Air can be easily bled out by “cracking” open a union
or loosening a fitting on a control valve, meter or pump housing.
When you do this, the system will need to be pressurized so you need to
exercise EXTREAM CAUTION, as there will be potentially Explosive Forces
present. Carefully loosen the component until a “hissing” is
heard, wait until water begins to spray out, then properly re-tighten
the component. Follow through with normal start-up procedures.