CEMP-E
TI 811-12
18 August 1998
CHAPTER 11
EQUIPMENT MODIFICATIONS
1. MODIFICATION GUIDELINES. UMCS implementation requires modifications to mechanical and
electrical systems and their associated instrumentation and controls. Interface to mechanical and
electrical systems will require coordination with manufacturer's operating recommendations and site
associated equipment/systems operating constraints.
2. INSTRUMENTATION AND CONTROLS. Existing local controls will be removed and replaced with
the application of DDC. For supervisory control applications existing local control system equipment will
be shown to include modifications required for interfacing with the UMCS. Except for existing time clocks,
the existing local loop control system must remain and perform as originally designed for UMCS
supervisory control applications. It will be necessary to indicate replacement of controllers to provide
capability for remote control point adjustment. The local loop controls will be interfaced so they will
operate in a predetermined manner upon UMCS failure. New sensors dedicated for UMCS use must be
shown as new rather than reusing existing sensors. When interfacing the field equipment, all existing
indicating devices such as gauges and thermometers will be shown as remaining in service for direct
digital control applications. The local controller will be replaced but the existing final control element
(valve/damper) will operate as originally designed.
3.
LOCAL CONTROLLERS UNDER SUPERVISORY CONTROL.
a. Existing local control systems using sensor, controller, and actuator require a controller with CPA
port for remote control point adjustment. This will necessitate the replacement of the existing controller
without CPA by a new controller with CPA. The CPA will be reset from an analog output.
b. Single input CPA controller. Single input CPA controllers permit remote changing of control
points by varying the CPA port value. CPA port value variation must be plus or minus 10 percent of
primary sensor span. The controller must include an adjustable setpoint, adjustable gain (proportional
band) with field selectable direct or reverse acting action. The controller inputs and outputs must have
internal or external gauges for calibration of input and output signals.
c. Two input controllers. Two input controllers permit remote changing of control points by varying
the second port input value. Effect of the secondary sensor on the setpoint is adjustable as a percentage
of the secondary sensor span, usually 33 to 100 percent of primary sensor span. The controller must
include an adjustable set point, adjustable gain (proportional band) with field selectable direct or reverse
acting action. The controller inputs and outputs must have internal and external gauges for calibration of
input and output signals.
4.
CONTROLLER INTERFACES.
a. Typical controller interfaces are shown in Appendix B .
b. A two-position pneumatic override incorporates a three-way solenoid to switch the signal to a
predetermined UMCS signal. The UMCS control signal value depends on the operation required and the
equipment being controlled. The existing control signal will operate the device being controlled during
field equipment panel failure. The UMCS control diagrams (Chapters 8 and 9) will define the failure
mode. The electrical equivalent to the two position pneumatic override is accomplished with a relay with
Form C contacts.
c. A three mode pneumatic override control incorporates two 3-way EP valves controlled from the
field equipment panel electrical output. The operation of the solenoids allows either for the dampers to be
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