Emerson Tescom ER5000 Series User Manual page 53

ER5000 — Glossary of Terms
Creep
An increase in the Outlet Pressure
a slow, gradual pressure increase. Indicates a regulator leak and calls
for the immediate removal of the regulator for service.
C v
The flow coefficient: equal to the number of U.S. Gallons of
water at 60°F / 16°C that will flow 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 modified to account for the
use of a compressible fluid. For a regulator, C v is determined when
the regulator is wide open and not regulating. When determining
actual performance during regulating conditions, use flow curves.
Decaying Inlet Characteristic
Also known as Supply Pressure Effect. The effect on the set
pressure of a regulator as a result of an
usually an increase in Outlet Pressure
inlet pressure.
In pressure reducing regulators, outlet pressure is set when force
from the load element, which opens the main valve, is matched
following Lock-up. Usually seen as
Inlet Pressure change;
due to a decrease in
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 flow, 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
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.
pressure equal to the Outlet Pressure
some additional pressure to activate: refer to
used with the ER5000 for low Control Pressure
Element. A diaphragm is sensitive
Pilot Pressure enters the dome at a
desired. Generally requires
Negative Bias. Can be
applications.
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