The Critical Chain Method was introduced by Eliyahu M. Goldratt in 1997 as a project management tool which differs from Critical Path and PERT methods. It is an alternative method to the standart and traditional methods in project management. In this article, we’ll analyze the principles of Critical Chain Project Management and its practicality to managing projects.
Successors of this project management tool claim it to be an alternative to the established standard of Project Management as advocated by PMBOK and other standards of project management.
The Critical Chain method is applied after the project schedule is prepared and the critical path determined . The determined critical path is reworked based on The Critical Chain Method. Then a resource-constrained critical path is determined which is altered from the original.
The Critical Chain Method considers the resource availabilities and their dependencies along all the task chain and adding buffers to the end of the chain. This method defines three types of buffers.
Project buffer is placed at the end of the project between the last task and the project finish milestone. If there is a delay on the critical chain, this buffer will act as a contingency to prevent the delays.
There can be lots of non-critical chains in a network. Feeding Buffers are placed at the end of the non-critical chains to match the duration of critical chain.
Resource buffer is a task which is placed before a critical chain task which requires critical resources such as labour, equipment etc.
As the project progresses, critical path changes and The Critical Chain should be recalculated. The Critical Chain method focuses on managing buffers in order to manage the manage and control the project schedule effectively.
Differences Between The Critical Chain Method and The Critical Path Method
In The Critical Path Method, all the activities are sequenced in a network system and the critical path is determined by making mathematical calculations. There are no overall buffers added to the critical path but while estimating the activity durations implicit buffers are added to each activity in order to protect schedule from delays. This may result too much buffers added to the schedule and cause an uneffective schedule.
In The Critical Chain Method, activity durations are estimated by considering minimal time needed to perform the activity. A Project buffer is placed at the end of the project between the last task and the project finish milestone which acts as a contingency to prevent the project from delays. This will provide a higher efficiency for estimating activity durations and resource needs. By the use of this method a more aggressive and efficient schedule can be obtained.
The Critical Chain Method enables to develop a more effective and agressive schedule by using the outputs of The Critical Path Method. This method helps to optimize resources and activity durations for a flexible and realistic schedule.