A production line is an important class of manufacturing system when large quantities of identical or similar products are to be
produced. The performance of a production line is highly influenced by machine failures. When a machine fails, it is then be unavailable
during a certain amount of time required to repair it. Analysis of production lines divides into three types: analytical, approximation and
simulation models. The analytical and approximation models have assumptions which make these models unrealistic such as reliable
workstations, certain processing distribution, the first workstation cannot be starved and the last workstation cannot be blocked. The main
problems in production lines treatment are the calculation of throughput and average levels of buffers because of the great size of state
space. An analytical model is reviewed to clarify the limitations to use such treatment in real production lines. Simulation modeling of
production lines is considered very important for designers interested in: Workload Allocation Problem (WAP), Server Allocation Problem
(SAP), and Buffer Allocation Problem (BAP). This paper studies and analyzes the performance keys, which effect on production lines. A
simulation model is developed by using ARENA software and used to analyze and test several bottlenecks that are causing severe
congestions in different areas on the production line and could resolve all of these bottlenecks. In this paper, an actual cement production
line is studied. After a simulation time of 13 days, a simulation results show the line bottlenecks, workstations utilization, buffer capacities
and the line production rate. The outputs clarify redesign of allocation of buffers, which verify an optimum size could be made; it might be
taken into consideration when designers implement such lines. Finally modified better workstations utilization, buffer capacities and the line
production rate with an increase about 15% of the production rate and economizing of 37 % from buffer capacities