Figure 2-1. Pump Or Compressor Discharge Pressure Control With Turbine Inlet Pressure Limiting - Woodward 505 Installation And Operation Manual

Manual 85017V2
Example 1–Pump or Compressor Discharge Pressure Control
with Turbine Inlet Pressure Limiting
Figure 2-1. Pump or Compressor Discharge Pressure Control with Turbine Inlet
This is an example of a typical pump or compressor application. With this
application the 505 is configured to normally control pump/compressor discharge
pressure, and limit governor valve position based on low turbine inlet steam
pressure. Both the Auxiliary and Cascade modes were used for this example
application. Other applications may or may not use all the functionality shown in
Figure 2-1 and described below.
With this application pump/compressor discharge pressure control is performed
within the 505 through the Cascade controller. Because the discharge pressure
being controlled, typically affects many other plant processes, a plant Distributed
Control System (DCS) may be used to monitor plant process conditions and set
the Cascade setpoint position. This can be performed through Modbus
communications, discrete raise and lower commands, or with a Analog setpoint
signal.
For this application a limiting type of control function was required to help
preserve inlet header pressure in case of system header problems. Because the
Auxiliary PID is the only controller that has this capability, it is used to sense
turbine inlet pressure and limit governor valve position, based on a low inlet
pressure setting.
Woodward
Pressure Limiting
505 Digital Governor
15