Tank filling pump

What you will build

Work order HS-2605. Harbour Steam Plant, Boiler feed tank T-201.

Harbour Steam Plant (power and utilities) needs a controller program for Boiler feed tank T-201. Fill a tank between two level switches without chattering, protect the pump from running dry, and latch an overflow alarm that needs acknowledging.

A pump fills the boiler feed tank from a sump. Three float switches in the tank read 1 when the water has reached them: Low_Level near the bottom, High_Level near the top, and High_High above that as the overflow warning. The sump has a float switch, Sump_Low, wired normally closed: it reads 1 while there is water in the sump and 0 when the sump is too low to pump from. Ack_PB is a momentary push button. The Pump must start when the level falls below Low_Level and keep running until the water reaches High_Level, then stay off until the level falls below Low_Level again: it must not start and stop as the level wanders between the two switches. The pump must never run while the sump is low; when the sump refills, the pump carries on if the tank is still below Low_Level. If the water ever reaches High_High (for example because High_Level has failed), the pump must stop, HH_Alarm must come on and stay on, and the pump must not run while the alarm is on. Pressing Ack clears the alarm only once the water has dropped below High_High. A press while the water is still at High_High does nothing and is not remembered.

What you will learn

• Latch and unlatch (OTL/OTU)
• Level control with hysteresis
• Dry-run protection
• Latched alarms and acknowledgement
• Read a short user requirement specification (URS) and turn it into ladder logic
• Prove your program against a numbered factory acceptance test (FAT)

How it goes

1. Read the work order and the URS.
2. Build the ladder program against the tag table.
3. Run the plant and watch it respond.
4. Run the FAT and fix whatever fails.

Tools

• Ladder editor in the browser

  Draw contacts, coils, timers and counters, then run the program.

• A working simulated plant

  Watch the machine respond as your logic runs.

• A tag table

  5 inputs and 2 outputs: Low_Level, High_Level, Sump_Low, High_High, Ack_PB, Pump, HH_Alarm.

• URS and FAT documents

  The paperwork a real project starts from, with numbered tests.

Questions

Is it free?

Yes. The lab is free to use with a free account. There is nothing to buy to open this scenario.

Do I need to install anything?

No. It runs in your browser with the ladder editor and a simulated plant.

What will I do in PLC-05 Tank filling pump?

You build and test a program, then check your work against an acceptance test.

How long does it take?

A first attempt takes about 50 minutes.

Do I need experience?

No. Each work order says what to do step by step, and hints are there if you get stuck.