Boiler Interlocks
medium
Combines pressure, level, and flame inputs into a burner permissive and reports which condition is blocking.
What it teaches
A safety permissive is a multi-input AND — every condition must be true for the burner to run. The industrial half: when the permissive is down, the operator needs to know why, so each condition also drives its own blocking-status flag. Teaches the interlock-plus-annunciator pattern every burner panel uses.
Inputs and outputs
| Tag | Type | Default | Description |
|---|---|---|---|
| In_Run | BOOL | — | Operator run request for the burner |
| In_Pressure | REAL | 5.5 | Boiler steam pressure in bar |
| In_Level | REAL | 60 | Drum water level in percent |
| In_FlameOK | BOOL | — | Flame safeguard healthy; 0 means a flame fault |
| Cfg_HiPressure | REAL | 8 | Pressure at or above this blocks the burner |
| Cfg_LoLevel | REAL | 30 | Level below this blocks the burner |
| Out_Burner | BOOL | — | Burner run command |
| Sts_Permissive | BOOL | — | 1 while every interlock is satisfied |
| Sts_PressureBlock | BOOL | — | 1 while high pressure is blocking the burner |
| Sts_LevelBlock | BOOL | — | 1 while low water level is blocking the burner |
| Sts_FlameBlock | BOOL | — | 1 while the flame safeguard is blocking the burner |
Required behavior
- Sts_PressureBlock is 1 while In_Pressure is at or above Cfg_HiPressure.
- Sts_LevelBlock is 1 while In_Level is below Cfg_LoLevel. A level exactly at Cfg_LoLevel does not block.
- Sts_FlameBlock is 1 while In_FlameOK is 0.
- Sts_Permissive is 1 only while all three blocking flags are 0.
- Out_Burner is 1 while In_Run and Sts_Permissive are both 1.
- The blocking flags report whether or not In_Run is 1, so the operator can see what is holding the burner before asking for it.
- More than one flag can be 1 at the same time. Each flag reports its own condition only.
- Nothing latches. When a condition returns inside its limit its flag clears at once, and Out_Burner resumes on the same run request.
- A change to Cfg_HiPressure or Cfg_LoLevel takes effect immediately.