# Plant

This chapter describes the **Plant** as the top structural level in the Selmo system.\
The goal is to **understand the entire plant as a unit** – independent of individual processes or stations.

The Plant forms the **global framework**in which all other elements exist.

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### Role of the Plant

The **Plant** represents the **entire machine or plant**.

It is:

* the top level in the Selmo model
* holder of global states
* place for plant-wide monitoring
* not responsible for processes

The Plant:

* describes **no sequences**
* contains **no state machines**
* makes **no process decisions**

> **The Plant defines the framework –**\
> **not the behavior in detail.**

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### Global states

At the plant level, states are described that:

* apply to the entire plant
* are independent of individual hardware zones
* are not tied to a specific process

Typical global states are:

* plant ready / not ready
* plant released / locked
* overall fault
* global safety state

These states:

* are visible to all subordinate levels
* influence their behavior indirectly
* are **not** controlled by sequences

> **Global states describe the plant context,**\
> **not the process state.**

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### Plant-wide CMZ

Certain conditions must **be valid for the entire plant at all times** be.

These are modeled as **plant-wide CMZ (Constantly Monitoring Zones)** .

Examples:

* main power supply
* central protective devices
* overarching safety releases
* plant-wide emergency stop states

Characteristics of Plant CMZ:

* permanently active
* state-independent
* override all subordinate levels

In case of a deviation:

* automation is locked plant-wide
* all hardware zones react deterministically
* there are **no movements possible anymore**

> **Plant CMZ protect the integrity of the entire plant.**

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### Distinction from hardware zones

For clear classification:

* **Plant**
  * describes the entire plant
  * manages global states
  * contains plant-wide monitoring
* **hardware zone**
  * describes a part of the plant
  * manages operating modes
  * starts and stops sequences

> **The Plant knows no processes.**\
> **Hardware zones know no entire plant.**

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### Placement in the overall model

The hierarchical structure is:

Plant\
└─ Hardware Zone\
└─ Sequence\
└─ Zone

The Plant:

* is above all hardware zones
* forms the stable upper closure of the model
* enables clear hierarchy and escalation

***

### Summary

The Plant is:

* the structural representation of the entire plant
* holder of global states
* place for plant-wide CMZ
* deliberately free of process and detail knowledge

> **The Plant creates order at plant level –**\
> **so that what is modeled below can be clear.**
