Module spare parts UNS0881a-P,V1 3BHB006338R0001

Focus on DCS, PLC, robot control system and large servo system.

Main products: various modules / cards, controllers, touch screens, servo drivers.

Advantages: supply of imported original products, professional production parts,

Fast delivery, accurate delivery time,

The main brands include ABB Bailey, Ge / fuanc, Foxboro, Invensys Triconex, Bently, A-B Rockwell, Emerson, AB91-1

UNS0881a-P,V1 3BHB006338R0001

Both the availability and the safety availability can be determined from a Markov model of the Tricon TMR PLC in the configuration described above. A Markov model uses a state diagram of various failure states of the system. From this model, the probability to be in any one state at a given time can be predicted. Using the combined probabilities of various failed states the mean time to failure due to a spurious trip (MTTF) and the probability of failure on demand (PFD) can be calculated for the system. These quantities are directly related to the availability and the safety availability. Failures can be generally classified into two categories: safe and dangerous. Safe failures are failures that result in the safety system failing into a safe configuration. For example, most safety systems including the Tricon TMR are designed to actuate upon complete failure of both power supplies. Dangerous failures are failures that result in the system failing to perform its intended safety function. Each category of failure can be further classifed into detected and undetected failures. Detected failures can be repaired on-line. Undetected failures are only detected and repaired during off-line periodic testing. 3.2.1 Model Description for Safe Failures. The Markov model for a safe spurious trip is shown in Figure 3-1. Note that this figure is developed using the methodology described in Reference 5. The Tricon TMR is a fail safe PLC with triplicated inputs (3-2-0), triple redundant main processor with communication, and a quad output voter. As required by Reference 1, the Markov model includes the main processor, a digital input module, an analog input module, a digital output module, and an analog output module. Along with each input/output microprocessor, the Markov model includes each input/output circuit. Also included is the dual power supply. The first state in the Markov model is the system operating normally with no failures. The intermediate states are when one channel of the various modules fail. The last state is when a second failure causes the system to trip spuriously. The probability of moving from one state to another (i.e., probability of failure or repair) are shown by the arrows. Note that constant failure and repair rates are assumed. Also time steps are assumed to be short so that the probability function can be estimated as shown bel