F-1031, Section 2119
Page 23 of 24
Balance Valve Function
The balance valve’s primary function is regulation of the
air circuit when operating the Auto-
Sync in the “AUTO”
mode.
The balance valve has 5 elements that work together to
provide regulation: air inlet, air outlet, diaphragm, water in-
let and piloted balance trim valve (BTV) (see Balance
Valve Elements)
Air enters the balance valve through the BTV and into the
inlet. This applies pressure to the diaphragm. On the other
side of the diaphragm is water pressure form the pump
discharge. The air pressure and water pressure opposes
each other against the diaphragm. As long as the water
pressure is greater than the air pressure on the dia-
phragm, the balance valve stays closed and no air passes
through. When the air pressure rises and becomes great
enough to overcome the water pressure, the diaphragm
moves allowing air to pass on through the outlet (see Bal-
ance Valve Open). The balance valve can be calibrated
(or biased) via the BTV. See control air control circuit cali-
bration in the maintenance manual.
How does the balance valve operate in the air control
circuit when in
the “AUTO” mode?
The balance valve basically operates as previously de-
scribed. If the compressor discharge pressure is above
water pressure (100 psi / 8.6 bar), then the piloted balance
valve opens allowing the control air pressure to close the
air inlet valve and lowering control air pressure below 100
psi (8.6 bar). When the discharge air pressure is below the
water pressure (again 100 psi) / 8.6 bar, the piloted bal-
ance valve closes. Now the control air pressure is not high
enough to keep the air inlet valve closed. The air inlet
valve opens allowing air into the compressor raising the
control air pressure above 100 psi (8.6 bar).
The balance valve opens and closes as needed so the
discharge air pressure matches the pump discharge water
pressure.
Balance Valve - Open
Balance Valve - Closed
Water Pressure
Air Pressure
Water Pressure
Air Pressure
Diaphragm
Air Inlet
Air
Outlet
Water
Inlet
