The model file Pond.gsm, found in the Reliability Examples folder in your GoldSim directory directory (accessed by selecting File | Open Example... from the main menu), is a simple model of a pond where the amount of water is controlled by three pumps. Water flows into the pond at a rate of 400m3/day, and it is pumped out of the pond by the three pumps.
In this model, we have a pond with an inflow rate of approximately 600 m3/day (the inflow is sampled daily from a Normal distribution with a mean of 600 m3/day and a SD of 100 m3/day).
Three pumps are used to remove this water. Each pump can only be operated if there is a sufficient depth of water in the pond (which varies from pump to pump). Pump_1 can only operate if there is more than 1.0m of water in the pond. Pump_2 can only operate if there is more than 2.0m of water in the pond. Pump_3 can only operate if there is more than 2.5m of water in the pond. The check to ensure sufficient water depth is done using a Condition type node in the External Requirements tree referencing the Water_Level element.
All three pumps can remove 300 m3/day and have an Exponential/Poisson failure mode with a failure rate of 1/3yr that is automatically repaired according to a Gamma distributed delay with a mean of 30 days and standard deviation of 10 days. The calculation of the water removed from the pond by the pumps is done using a series of if/then/else statements referencing the condition of each pump. For example, the contribution of Pump_1 is calculated using the following if/then/else statement:
if (Pump_1 = RL_Operating, 300 m3/day, 0 m3/day)
The result of this statement is added to the result of similar statements for Pump_2 and Pump_3 to determine the Rate of Withdrawal from the Pond element.
The time history of the water level in the pond over the course of the simulation looks like this:
The plot shows that for the most part, the level of the pond is controlled at about 2.4 meters. However, spikes as high as 8 meters can occur when the pumps fail.