Installation and Operation Manual
Urano - Pressure Regulating Valve
MI-31
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CSQ
Data
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JJ
JJ
JM
05/07/21
05
11 de 74
3.2 REGULATOR SPRING TO OPEN (FAIL OPEN)
During pressure absence, shutter (A) is kept in the open position by the main regulator (B) spring, which keeps it away
from the gasket (C). It stands out that even when subject to pressure, upstream pressure variations have no influence on
the shutter position, due to the balancing of the forces acting on the same, as well as on the actuator shaft (D) that is also
balanced.
When the inlet piping is pressurized, gas passes through the filter element and reaches the pre-regulator (booster) (F), which
reduces the pressure to a convenient value near to the outlet pressure value and delivers the same to pilot (G). It is important to note
that unlike to the URANO FAIL CLOSE regulator, the pressure provided by the booster is injected also directly in the diaphragm upper
chamber. This is necessary for the regulator to close under normal operating conditions, since the main regulator spring is pressing the
shutter for it to stay in the open position.
The pilot compares the output pressure sensed by the diaphragm (H) and controls the flow to be injected under the
main regulator (L) diaphragm to open the valve.
If a decrease in the downstream pressure occurs (due to an increased consumption or a drop of the upstream pressure)
an imbalance between the spring (I) force on the pilot diaphragm (H) and the force generated by the outlet pressure under
this same diaphragm, drives the pilot (K) shutter to a larger aperture, therefore, causing a pressure increase under the
main regulator (L) diaphragm, determining the displacement of the shutter (A) upwards, thereby increasing the passage
and restoring the set point pressure.
When the setup pressure begins to increase, it requires the pilot (K) shutter to reduce the aperture. The higher pressure
that operated under the regulator (G) diaphragm flows through the Bleed (M) restriction (adjustable) that discharges the
same downstream, thereby causing the pressure to actuate on the diaphragm to be larger than the combined pilot force
and spring force, moving the shutter down and shutting the main valve.