Micromod MOD: 1800P - MOD 30ML Identity Module (Version 2) Algorithms, Tables and Sequential Logic Functions - Manual (Page 148)

Logic Functions - Book 2
CONFIGURING THE SEQUENCE BLOCK
11-2
11.2.1 Sequence Description
The operations necessary to cook a batch of product require six basic steps. The steps and
the actions determining the progression from one step to the next are shown in the flow chart,
Figure 11-2.
Yes
No
Yes
Is Kettle
Full
?
Yes
No
Operator Presses
Start Button
Step 1
Process is Idle
Step 2
Open Fill Valve
and Fill Kettle
Is
Start Button
Pressed and
Drain Valve
Closed
?
Step 3
Close Fill Valve
and Set PID Controller
Setpoint at Cook
Temperature
Step 4
Cook
Product
Step 5
Change Controller
Setpoint to Cool
Step 6
Open Drain Valve
Close Drain Valve
Is Product
Temperature at
Setpoint
?
Is Draining
Finished
?
Is Product
Cool
?
Is Cook
Finished
?
Yes
No
Yes
No No
No
Yes
At the start of a sequence, the process is idle on Step
1. An operator starts the sequence using a push button
symbol on a CRT screen. If the drain valve is closed,
the sequence advances to Step 2.
In Step 2 the fill valve is opened and the kettle starts
to fill. When the rising level trips the high level switch
(LSH), the sequence advances to Step 3
In Step 3 the fill valve closes, the drain valve remains
closed, and a setpoint value of 250°F is sent to a
temperature controller (the controller configuration is
not part of this example). The product begins to heat.
When the temperature reaches the setpoint the
sequence advances to Step 4.
In Step 4 the product is held at the cook temperature
for 1 hour. At the end of the cook time, the sequence
advances to Step 5.
In Step 5 the temperature controller setpoint is changed
to 100°F and the product is allowed to cool. When the
temperature reaches the cool setpoint, the sequence
advances to Step 6.
In Step 6 the drain valve is opened allowing the finished
product to drain from the kettle. When the low level
switch (LSL) is tripped, the drain valve closes. The
sequence is reset to Step 1 and the process remains
idle until the operator pushes the start button again.
Figure 11-2. Sequence Flow Chart