3329 Manual
KOBELT MANUFACTURING CO. LTD
Rev A
MNL-3329.docx
6
2.2
B
ASIC
O
PERATING
P
RINCIPLE
The purpose of the 3329 relay valve is to
amplify the volume of air from a variable
pressure source while following the pilot
pressure signal with minimal error. The valve
uses a large diaphragm to maintain balance
between the pilot pressure and sensed
actuator pressure. The diaphragm makes
these valves very accurate due to the low
friction.
The pilot pressure entering the pilot port
applies a force on the diagram and spool
assembly. When this force exceeds the
cracking pressure, the spool moves
downward and opens the inlet poppet
thus
allowing air to flow to the “OUT” port (see
Fig. 2).
Air pressure goes to the “OUT” port and via
an orifice, also to the pilot chamber. The air
accumulating on the underside of the
diaphragm until such a point that the
pressures on both sides of the diaphragm are
equal and the spool moves back to its neutral
position and the inlet poppet closes again.
This will cause an equilibrium point whereby
no air flow will take place.
Reducing the pilot pressure to a value less
than the outlet pressure will cause the spool
to move upwards and lift itself from the inlet
poppet seat and permit exhaust of air to
atmosphere. This will permit the outlet air to
also exhaust until the valve is in a balanced
position again.
Figure 2: Principle of Operation
