ER5000 —
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Glossary of Terms
Creep
An increase in the Outlet Pressure following Lock-up. Usually seen as
a slow, gradual pressure increase. Indicates a regulator leak and calls
for the immediate removal of the regulator for service.
C
v
The ow coefcient: equal to the number of U.S. Gallons of
water at 60°F / 16°C that will ow through a valve, regulator or
restriction in one minute when the pressure differential between
inlet and outlet is one pound per square inch (1 psi). When gas is
used instead of liquid, the equation is modied to account for the
use of a compressible uid. For a regulator, C
v
is determined when
the regulator is wide open and not regulating. When determining
actual performance during regulating conditions, use ow curves.
Decaying Inlet Characteristic
Also known as Supply Pressure Effect. The effect on the set
pressure of a regulator as a result of an Inlet Pressure change;
usually an increase in Outlet Pressure due to a decrease in
inlet pressure.
In pressure reducing regulators, outlet pressure is set when force
from the load element, which opens the main valve, is matched
by inlet pressure moving through the valve. If inlet pressure
decreases, for example when a supply cylinder starts to empty
and the inlet pressure it supplies starts to decrease, this tips the
balance in favor of the load element and opens the valve wider.
This allows more ow, which results in a higher output pressure
and the seemingly paradoxical fact that a decrease in inlet
pressure results in an increase in outlet pressure.
Two-stage regulator design or the use of PID controllers, can
prevent this characteristic.
Diaphragm
One of several types of Sensing Element. A diaphragm is sensitive
in reacting to pressure changes. Common diaphragm materials are
Buna-N, Viton, Ethylene Propylene, 316 Stainless Steel and Elgiloy.
Dome Loaded
One type of Loading Element. Pilot Pressure enters the dome at a
pressure equal to the Outlet Pressure desired. Generally requires
some additional pressure to activate: refer to Negative Bias. Can be
used with the ER5000 for low Control Pressure applications.
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