Ageing chain - Timing process

[Steve]

Hi,

In attachment you will find an ageing chain of the bulk fleet. The idea is that i want to distinguish between the fleet (stock of vessels) and the active fleet. Their difference is in the Lay up of vessels (happens when age fleet > marginal age vessel).

I succeeded in modelling this albeit their is some problem. I want to calculate the time the vessel is in Lay up (now this happens (discrete) each time step by the decision to lay up or not). If a vessel is eg. 4 months in lay up, it will be scrapped. Then this vessel has to leave the fleet also.

Can you calculate in the diagram how to calculate the time a vessel is in lay up, and how to exit those vessels (which are too long in lay up) from the fleet stock.

Thanks in advance,

Steve

[bob@vensim.com]

I would recommend that you study the model maint1.vmf that comes with Vensim - specifically the parts failure process. This deals with all the issues you seem to need to deal with, through the names are different. See also John Sterman's book and look up coflows.

This is an aggregate representation. If you want to track attributes of individual ships it may be easiest to subscript the model by ship then you can know in detail information about all the ships.