The storage tank system shown in the below figure is used to store process feedstock. Overfilling of storage tanks is a common problem in the process industries. To prevent overfilling, the storage tank is equipped with a high-level alarm and a high-level shutdown system. The high-level shutdown system is connected to a solenoid valve that stops the flow of input stock.

(a) Develop an event tree diagram for this system using the failure of level indicator as the initiating event. Given that the level indicator fails 4 times/yr, estimate the number of overflows expected per year.

(b) Compute the probability of failure and reliability for the level indicator system

Use the following data:

System	Failures/demand
High-level alarm	0.01
Operator stops flow	0.1
High-level switch system	0.01