Doc: ps2001-5-1101-001 Rev: R02. 00

Doc PS Rev Rb
Application Modules
Application
modules will be project specific modules and will be written and configured fora particular project and the requirements of that project. This approach is best explained with an example to illustrate the desired concept. Consider a control system that is required to control and monitor various devices and instruments that are part of the simple filtration plant shown in Figure 2.1. This example filtration plant has the following types and quantities of valves MOTORISED VALVES QUANTITY 2 DEVICE
T
AG
D
ESCR IP TI ON MV101 Filter 1 inlet valve
MV201 Filter 2 inlet valve Table 2.1 Example filtration plant equipment — Motorised valve MODULATING VALVES QUANTITY 2 DEVICE
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AG
D
ESCR IP TI ON CV Filter 1 outlet valve CV Filter 2 outlet valve Table 2.2 Example filtration plant equipment — Modulating valve ISOLATING VALVES QUANTITY 6 DEVICE
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AG
D
ESCR IP TI ON VV103 Filter 1 backwash water inlet valve
VV104 Filter 1 backwash water outlet valve
VV105 Filter 1 Air inlet valve
VV203 Filter 2 backwash water inlet valve
VV204 Filter 2 backwash water outlet valve
VV205 Filter 2 Air inlet valve Table 2.3 Example filtration plant equipment — Isolating valve

18-71 Doc PS Rev R Figure 2.1 Example filtration plant schematic

Doc PS Rev R 19-71 It has the following drives DRIVES QUANTITY 4 DEVICE
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D
ESCR IP TI ON BL Backwash blower 1 BL Backwash blower 2 PM Backwash pump 1 PM Backwash pump 2 Table 2.4 Filtration plant equipment — Drives And the following instruments INSTRUMENTS QUANTITY 3 DEVICE
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AG
D
ESCR IP TI ON FIC101 Filter 1 outlet flow
FIC102 Filter 2 outlet flow LIT Backwash tank level Table 2.5 Filtration plant equipment — Instruments In summary, this example filtration plant has the following types of devices and instruments Motorised valves (open/close valve driven by a motor)
•
2 × Modulating valves (can beset to any position between opened and closed)
•
6 × Isolating valves (open/close valve usually by a solenoid)
•
4 × Drives (simple start/stop motors)
•
3 × Instruments
I.e. it has five different types of devices and instruments.

20-71 Doc PS Rev R If this were to be programmed using the PAL, five
standard
modules would be needed one for each type of device
• Standard module for motorised valves
• Standard module for modulating valves
• Standard module for isolating valves
• Standard module for drives
• Standard module for instruments It would also have five project specific
applications
modules:
• Application module for motorised valves
• Application module for modulating valves
• Application module for isolating valves
• Application module for drives
• Application module for instruments The first of these (for motorised valves) would call the
standard
motorised valve module two times (once for MV101 and once for MV201) and each instance would link the standard module to the particular physical input and output (IO) signals and internal storage locations associated with the motorised valve in question. Similarly, the
application
module for modulating valves would call the
standard
mod- ulation valve module twice (once for CV and once for CV. The isolating valve
application
module would call the
standard
module (for isolating valves) six times (for VV103, VV104, VV105, VV203, VV204 and VV205). And soon. The contents of each
application
module would be dependent on the requirements of the plant being controlled (specifically how many of each type of device exist. I.e. the

Doc PS Rev R 21-71
application
modules differ between different projects the
standard
modules on the other hand are the same across all projects. In the above (filtration) example, the application modules are simply coordination areas that call the required
standard
modules the requisite number of times. There would clearly be more to the Controller programme than this, something must decide when a valve is to be opened, a drive started c. and in the case of the modulating valves something must decide what position the valve should adopt. The type of logic that performs these actions is either continuous logic (operates all the time) or sequential logic (operates as part of a sequence. In this case, the filter would normally operate under continuous control (the inlet valve would open and the modulating outlet valve position adjusted to maintain a specific flow from the filter. At some point, the filter will be need to be cleaned (probably at a specific time of day the continuous logic would (when the specific time was reached) trigger a cleaning sequence that would then take control of the filter and clean it. Atypical sequence would be
• Isolate the filter (take it out of service and close all valves)
• Aerate the filter (open air inlet valve and start blower)
• Backwash the filter with aeration (open backwash inlet and outlet valves and start backwash pump)
• Washout the filter (stop blower and close air inlet valve)
• Allow filter bed to settle (stop pump and close backwash valves)
• Return filter to service (open inlet and outlet valves) These modules (continuous logic modules and sequential control modules) are also
application
modules.