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STI S.r.l.
– Via Dei Caravaggi 15, 24040 Levate (BG) – ITALY www.imi-critical.com
Manual 2071, rev.07 02/2019
– BV
8
6
OPERATION AND USE
6.1 Operation description
Big Volume Booster BV has 2 main setups: charge (figure 4, 5, 6) and discharge (figure 7, 8, 9). The valve
shutter may create a pressure drop depending on its adjustment and the working fluid flow rate.
In the charge setup the working fluid from the pilot passes through the valve shutter:
a) if the flow rate is lower than a threshold value depending on valve shutter adjustment, the valve shutter
throttling can’t generate a pressure drop between the two side of the piston and the working fluid goes
to the actuator chamber.
This case is called “stand-by mode” (figure 4);
b) if the flow rate is greater than a threshold value depending on valve shutter adjustment, the valve shutter
throttling generates a pressure drop between the two side of the piston and the working fluid pushes
down the piston and the lower shutter, allowing the connection between the BV supply chamber and the
actuator chamber.
This case is called “modulating mode” (figure 5);
c) if the flow rate is much greater than a threshold value depending on valve shutter adjustment, the valve
shutter throttling generates a pressure drop between the two side of the piston and the working fluid
pushes down the piston and the lower shutter, allowing the connection between the BV supply chamber
and the actuator chamber. In this case the lower shutter generates the greatest flow section available
because the piston reaches its lower stroke limit. This case is called “on-off mode” (figure 6).
In the discharge setup the working fluid from the actuator passes through the valve shutter:
a) if the flow rate is lower than a threshold value depending on valve shutter adjustment, the valve shutter
throttling can’t generate a pressure drop between the two side of the piston and the working fluid goes
to the pilot. This case i
s called “stand-by mode” (figure 7);
b) if the flow rate is greater than a threshold value depending on valve shutter adjustment, the valve shutter
throttling generates a pressure drop between the two side of the piston and the working fluid pushes up
the piston, allowing the connection between the actuator chamber and the exhaust chamber. This case
is called “modulating mode” (figure 8);
c) if the flow rate is much greater than a threshold value depending on valve shutter adjustment, the valve
shutter throttling generates a pressure drop between the two side of the piston and the working fluid
pushes up the piston, allowing the connection between the actuator chamber and the exhaust chamber.
In this case the upper shutter generates the greatest flow section available because the piston reaches
its u
pper stroke limit. This case is called “on-off mode” (figure 9).
