Failure analysis is as follows:
1. The control system can operate normally when the controlled object has the characteristics of saturation nonlinearity (e.g., temperature control system). Or small flow control system is very sensitive, and even oscillation and instability, but in the large flow, the control system can operate normally. Fault reason is the selection of the linear or fast open flow characteristics of the control valve. Fault processing method is to replace the control valve of the valve or control valve, or valve installation f Diao positioner, so that control valve to meet the percentage or parabolic flow characteristics.
2. The controlled object has a linear characteristic (for example, the flow control system) O small flow control system is operating normally, large flow control system appears oscillation or unstable phenomenon. Or small flow control system is stagnant, large flow control system to be able to operate normally. Fault causes are selected such as the percentage of the flow characteristics of the control valve. Fault processing method is to replace the control valve of the valve or control valve, or the installation of the valve positioner, so that the control valve to meet the requirements of linear flow characteristics.
3. Control valve rated flow coefficient selection. The rated flow coefficient is too large or too small, so that the control valve can be adjusted to the minimum or maximum flow becomes large or small, can not meet the operation requirements of process production process. Control valve in the small opening or opening position, control quality variation.
Fault processing method is to re - check the control valve flow coefficient, the installation of the control valve to meet the requirements. For example, directly according to the process pipe diameter selection control valve caused by excessive flow coefficient is too large, due to the expansion of production scale caused by the rated flow coefficient is too small, and so on.
