Design and implementation of PLC systems
From Wikiversity
Template:Manufacturing Outline of an Approach Manufacturing process, systems, equipment Acquire pre-existing specifications for system components and behavior
- Site Layout Plan
- Wiring Diagrams
- Component specifications and constraints
- System and component behavior and constraints
- Process and instrumentation diagrams
Design the system and draft P&IDs (Process and Instrumentation Diagrams)
Assign I/O and memory ports
- Document for system manuals
Program PLC
- Ladder Logic
- other
Create user and maintenance manual
Test PLC code
Install system in field
Field test entire system
Contents |
[edit] External References
- http://en.wikibooks.org/wiki/Introductory_PLC_Programming
- http://en.wikibooks.org/wiki/Relay_ladder_logic
[edit] Design Challenges
A manufacturer who dyes a lot of cloth has a requirement to process waste water to oxidize the organics in the waste water before dumping the waste water into a nearby large river. It already has a waste water processing pond but the bugs keep dying off over the weekend when no feedstock is arriving as waste from the factory. Environmental engineers have decided to build a 300,000 gallon holding tank to smooth out the flow to improve the ponds performance. Average outflow during the middle of the week is 300 gallons/minute with occasional peaks (to avoid emergency overflow of holding tank) of 1200 gallons per minute.
A control valve will be used to smoothly control the outflow into the pond. In normal operations, stock should be built up on thursday and friday to enter the weekend with a full tank without any emergency overflow.
Water flows through a rotary strainer into a 20,000 gallon wet well. From the wet well two of three 600 gallon per minute pumps on a rotating basis pump water to the holding tank. The pumps specifications require a 5 minute cool down period after operating or any attempt to start pumping. Failure to meet these specifications voids warranty and could permanently damage or destroy the pump.
Fluid flows as vats are dumps during mid and end shifts at up to 3,000 gallons per minute at up to fifteen minutes at a time in a linear ramp pattern from 3000 to 0 gallons/minute.
Level monitoring is required in the tank with alarm alerting to bring abnormal operating conditions to the maintenance personel's attention.
Design an instrumentation and control system using a PLC and any appropriate instrumentation to control the equipment listed throughout the work week. Address holidays and 3 day weekends.
