Function Block Description

Function Block Description - CavtProt

Pin Diagram

Brief Description

The CavtProt function block helps to avoid operating the VS and FS pumps in a cavitation situation. To achieve this, it constantly verifies the suction pressure in the pumping application and adapts the setpoint of the PID control function, if necessary. If in spite of this measure the suction pressure drops below the NPSH+ value, the CavtProt function block indicates a detected alarm, induces the stop of the pumping application, by setting the iq_stAlrmCtrl.xAlrmRele bit to FALSE (0) to help avoid pump damage.

I/O Variables Description

The table describes the input/output variables of the function block:

Input/Output	Data Type	Description
iq_stAlrmCtrl	stAlrmCtrl	Structure used for alarm handling. Refer to the structure data type description.
iq_stOpMode	stOpMode	Determines the operating modes. If the element xAuto of the structure data type stOpMode is set to TRUE, the function block executes its tasks automatically. With another status of this element, the outputs of this function block are set to their defined fallback (default) states. Refer to the structure data type description.
iq_stCavtInit	stCavtInit	Structure used for initialization data for the cavitation protection function. Refer to the structure data type description.

Input/Output

Data Type

Description

iq_stAlrmCtrl

stAlrmCtrl

Structure used for alarm handling. Refer to the structure data type description.

iq_stOpMode

stOpMode

Determines the operating modes.

If the element xAuto of the structure data type stOpMode is set to TRUE, the function block executes its tasks automatically. With another status of this element, the outputs of this function block are set to their defined fallback (default) states. Refer to the structure data type description.

iq_stCavtInit

stCavtInit

Structure used for initialization data for the cavitation protection function.

Refer to the structure data type description.

The table describes the input variables to the function block:

Input	Data Type	Description
i_xRele	BOOL	Activates (TRUE) or stops (FALSE) the execution of the function block.
i_stAna_SuctPres	stAna	Structure used for the analog suction pressure input value and the state of this value. Refer to the structure data type description.
i_rSp	REAL	Contains the user-defined pressure setpoint. This constant setpoint is considered during startup (pipe fill function) of the pumping process. It is adapted by this cavitation function and can be adapted by other functions of this library, if used (ComSp and CompSpFLow). To help to prevent a cavitation situation, this value is adjusted by the CavtProt function block. The adjusted setpoint is provided by the output parameter q_stRef_Sp.

Input

Data Type

Description

i_xRele

BOOL

Activates (TRUE) or stops (FALSE) the execution of the function block.

i_stAna_SuctPres

stAna

Structure used for the analog suction pressure input value and the state of this value.

Refer to the structure data type description.

i_rSp

REAL

Contains the user-defined pressure setpoint. This constant setpoint is considered during startup (pipe fill function) of the pumping process. It is adapted by this cavitation function and can be adapted by other functions of this library, if used (ComSp and CompSpFLow).

To help to prevent a cavitation situation, this value is adjusted by the CavtProt function block. The adjusted setpoint is provided by the output parameter q_stRef_Sp.

The table describes the output variables from the function block:

Output	Data Type	Description
q_stRef	stRef	Structure for setpoints contains the adapted pressure setpoint and the state of this value. Refer to the structure data type description.
q_stCavtSta_Hmi	stCavtSta	Structure that is used to display the status of the cavitation protection function on the HMI. Refer to the structure data type description.
q_stCavtErr	stCavtErr	Structure used for states of alarms and alerts detected by the cavitation protection function. Refer to the structure data type description for detected cavitation protection alarms.

Output

Data Type

Description

q_stRef

stRef

Structure for setpoints contains the adapted pressure setpoint and the state of this value.

Refer to the structure data type description.

q_stCavtSta_Hmi

stCavtSta

Structure that is used to display the status of the cavitation protection function on the HMI.

Refer to the structure data type description.

q_stCavtErr

stCavtErr

Structure used for states of alarms and alerts detected by the cavitation protection function.

Refer to the structure data type description for detected cavitation protection alarms.