Proportional_Valve Function Block
This figure shows the pin diagram of the Proportional_Valve function block:
The Proportional_Valve function block is used for controlling proportional valve.
The Proportional_Valve function block supports three operating modes:
oAutomatic Mode: The automatic mode is activated by the input pin i_xAut. In this mode, the valve is opened and closed via the input i_xMove, regardless if the local mode is activated or not. The new set point is given at the input i_rSp.
oManual Mode: The manual mode is activated by the pin i_xMan.
Case 1: Local mode is not activated. The valve is opened and closed through a bit command in the variable i_dwCtrl and the value of the set point is given by rSP on the input-output iq_strHmi
Case 2: Local mode is activated. The valve is operated through the inputs i_xManOpen and i_xManCls.
oLocal Mode: The local mode is activated by an input pin i_xLoc and is set additionally to the automatic or manual mode. The local mode does not influence the automatic mode, but changes the source for manual operation. The output q_iValvPos is automatically set to i_strPara.rMinSp when using i_xManCls or i_strPara.rMaxSp when using i_xManOpen.
NOTE: If the operation mode is changed from manual or HMI mode to automatic mode, a movement of the valve is stopped. Any other change of the operation mode does not affect the valve movement, but the setpoint is adjusted to the value of the actual operation mode.
The output q_xMove remains active as long as the new position given by the setpoint is not reached.
A deadband can be set by i_strPara.rBnd, so that q_xMove is switched Off, when the deviation of actual position and setpoint is less than the deadband.
When using the inputs i_xManOpen and i_xManCls in local mode, the output q_xMove is active as long as the inputs are active or if the maximum or minimum position is reached (taking dead band into consideration).
The position of the valve is supervised by the feedback signals i_xFbckOpen and i_xFbckCls. Once the operation is started, the feedback inputs must signal the right position of the valve within a defined time. If this time exceeds, then the block indicates a detected error. The time can be set through the structure element iFbckDly at input i_strPara. The supervision can be switched Off by the structure element xFbckEn at the input i_strPara.
The valve can be operated if the input i_xLock is set to 0. An active interlock signal inhibits the operation of the valve. An active interlock is indicated by the output q_xLock.
The valve can only be operated, if the output q_xErr is set to 0. An active detected error signal inhibits the operation of the valve.
The output q_xErr is high if an error is detected. The detected error can be:
oInternal detected error (invalid operation mode, missing feedback signal or unknown position.
oExternal detected error
The detected errors are indicated in the HMI as alarms. If an interlock or an error is detected during the operation of the valve, the behaviour of the function block depends on the structure element i_strPara.xFrceEn at input i_strPara. If this element is set to 1, the block enforces the valve to move in to the default position, and the output is high (q_xMove) for the duration of i_strPara.iFbckDly seconds. Otherwise the operation is stopped and has to be restarted after the interlock is gone.
To reset the q_xErr, the detected error has to be acknowledged by a rising edge on the input i_xAckn or by using bit 16 of the signal i_dwCtrl.
The default position of the valve can be set by i_strPara.xPosDfltSet. This description assumes Close as default. If i_strPara.xPosDflt is set to 1, Open is the default position.
