Design and Implementation of HC900 Control System - Allowable Function Blocks for Process and Safety Functions
28 HC900 Process & Safety Controller Safety Manual Revision 1.9
01/14
Min-Max-Avg-
Sum
Accepts inputs from up to six analog input values (X1
- X6) and calculates these values for output: Minimum
input value, Maximum input value, Average of input
values, SUM of input values, Standard Deviation
value, Alarm output for deviations. Turns ON ALM
when any input is outside the configured number of
standard deviations when the configuration parameter
DEV > 0.
X
X
Negate
Convert a value to the opposite sign value. i.e., +5 in
= - 5 out, -6 in=+6 out.
X
X
Dewpoint
Monitors Dewpoint or Carbon Potential, or uses a
Zirconia Probe sensor input to supply a Dewpoint PV
to a PID function block for Dewpoint control. Use in
conjunction with other blocks including a PID to
generate more elaborate control strategies than that
provided by the Carbon potential (CARB) function
block.
X
Totalize
Integrates an Analog variable using a specified rate.
Rate may be in units per minute, hour, or day. A
preset is provided to reset the value when a specific
quantity has been accumulated and provides a digital
status output. Separate digital enable and reset
inputs are provided. Accumulated value may
increment from 0 to preset for increasing totals or
decrement from the preset to 0 for decreasing totals.
X
X
Continuous
Average
Provides the average value of a single analog
parameter for a user specified time period, plus the
running (instantaneous) average within the time
period. Running average value is updated at the end
of each sample period. Time periods to 1440.0
minutes are supported. At the end of the time period,
the running average value is transferred to I/O
process output. Hold input allows excluding samples
from the average when active. Cold Start – On the
first cycle after a cold start, the instantaneous
average output is initialized to current input value, the
sample counter begins to increment, and the period
timer begins to decrement (assuming that Reset is
OFF). The previous average output is set to zero.
Warm Start – On a warm start, the calculations
continue where they left off. There is no attempt to
compensate for the time the power was off or to
resynchronize with the time of day.
X
X
AGA8 Detail
The Detail method (AGA8DL) uses the gas analysis
of up to 21 components. From the gas analysis, the
super-compressibility factor, gas density at flowing
and standard conditions, and gas relative density at
standard conditions are calculated for input into the
AGA calculation for the meter type chosen. Used
when accurate gas analysis is available either via an
on-line gas analyzer or from laboratory
measurements. The Detail method can handle up to
21 gas components typically found in natural gas. If
this information is available, the Detail method is
preferable, as accurate results are obtainable over a
wider range of conditions than the Gross method.
X
To Next Page
Loading...
