Basic concept
In a double flame tube boiler, two burners are operated with two flame tubes in one boiler:
The following modes are distinguished:
Note
Both HMIs must be connected to one another via an Ethernet cable.
Only parallel operation
In this mode, both burners are basically operated in parallel over the entire capacity range. The system behaves as follows:
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Both burners are always started together.
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The two burners purge and ignite simultaneously.
Cross wiring on the FSCs is required in order to ensure this. To do so, the "purge position reached" and "ignition position reached" outputs on one of the FSCs are wired to the "external purge position reached" and external ignition position reached" inputs of the respective other FSC.
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Synchronous run monitoring is active. This means that a load difference is only possible within an adjusted tolerance range.
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A safety shut-off on one burner automatically leads to a safety shut-off on the other burner (except when emergency operation is active).
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The load position of one burner is determined by the setting value of the other burner.
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Single operation is not possible.
Parallel operation
Both burners can be operated in parallel via one of the two HMI or DI/BUS modules. Regardless of the HMI used for operation, it always applies to both burners in parallel.
Example
Both burners are stopped automatically if the operator stops the burner on HMI1.
Manual operation
Manual operation can be activated for the burners if necessary. As soon as the operator activates manual operation for one burner, it is also activated for the other burner. However, manual mode behaves differently in parallel operation than in single operation:
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Parallel manual operation
The manual load demand which the operator specifies for a burner applies concurrently to the other burner.
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Single Manual Mode
The operator can adjust the load demand separately for each of the two burners (e.g. burner A: 30 %, burner B: 70 %). DFT: Single Manual Mode: Trip at load load difference is used to define whether a safety shut-off is triggered if the load difference between the two burners set in parameter DFT: Parallel operation: Maximum load difference is exceeded. A separate user level can be defined for single manual operation.
Emergency operation
If a safety shut-off occurs on one burner, it is nevertheless possible to allow the other burner to keep firing. Emergency operation can be parameterized for this purpose.
In emergency operation, the other burner continues firing at a reduced load (individually parameterized via DFT: Single operation: Load limitation).
This requires that communication via the Ethernet connection remains active.
The burner which is firing in emergency operation is automatically switched to burner OFF as soon as the fault is rectified and the burner reset. Then both burners are restarted. This ensures that purging, ignition and firing of the burners takes place simultaneously again.
Parallel and single operation
If the design of the boiler also permits single operation of the burners, then these can be operated both in parallel and singly. In this case the operator can select the required operation mode in the burner operation.
Parallel operation
Parallel operation in this mode largely behaves the same way as parallel operation in "Parallel operation only" mode. Differences exist in manual operation and emergency operation, however.
Single operation
Only one burner is firing at any time if single operation is activated. A maximum load limit can be defined for this burner, in order to prevent the burner from firing at full load and thus potentially causing damage to the boiler.
Manual operation
Manual operation can be activated for the burners if necessary. As soon as the operator activates manual operation for one burner, it is also activated for the other burner. However, manual mode behaves differently in parallel operation than in single operation:
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Parallel manual operation
The manual load demand which the operator specifies for a burner applies concurrently to the other burner.
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Single Manual Mode
The operator can adjust the load demand separately for each of the two burners (e.g. burner A: 30 %, burner B: 70 %). DFT: Single Manual Mode: Trip at load load difference is used to define whether a safety shut-off is triggered if the load difference between the two burners set in DFT: Parallel operation: Delayed shut-down for load difference is exceeded. A separate user level can be defined for single manual operation.
Emergency operation
If a safety shut-off occurs on one burner, it is nevertheless possible to allow the other burner to keep firing. Emergency operation can be parameterized for this purpose.
In emergency operation, the other burner continues firing at a reduced load (individually parameterized via DFT: Single operation: Load limitation).
The burner is restarted as soon as the fault has been rectified and the burner reset. Then both burners synchronize automatically.