Critical Chain Project Management Methodology and Buffers Explained
The age old problems the Project Managers face is exceeding their Project Schedule. This is a general problem that almost always happens in during project management. To solve this, the project managers usually plan for a buffer duration in the project schedule so they don’t exceed their Schedule and sometimes, even with this buffer, they end up getting delayed. These delays are caused by bottlenecks in various phases of the project.
Critical Chain Method (CCM) or Critical Chain Project Management (CCPM) extends from Theory of Constrains (TOC) which focuses on identifying the constrains and bottlenecks in the system to improve the throughput. As an outgrowth of TOC, Critical Chain Method also tries to identify and eliminate these constrains and bottlenecks to make sure there are no delays in the project and that it doesn’t extend the project schedule.
Critical Chain Project Management (CCPM) focuses on planning and managing projects which give special important to the resources required to execute project tasks.
The main advantage of CCM over other traditional Project Management Methodologies is that, Critical Chain Method focuses on getting the project done early and meet the Project Schedule strictly.
What is Critical Chain and Critical Chain Project Management?
The critical chain can be defined as “the longest path in the network diagram considering activity interdependence and resource constraints.” Basically critical chain is the longest path in project management which prevents the project from being completed in the shortest time assuming infinite resources are available for the task.
The critical chain method is a modified form of Critical path method which considers the availability of resources when making the project schedule.
The main advantage the critical chain method has over the Traditional Project Methods like Waterfall is how the uncertainties are managed. In traditional method, tasks are padded with extra time and starting each task as soon as possible and doing parallel activities to solve the uncertainties. In Critical Chain scheduling, uncertainty is primarily managed by estimating the average time duration for a task and scheduling these tasks and leaving out all the unnecessary tasks to save time. Aggregate buffers are placed in the project plan to protect the entire project and the key tasks; and buffer management is done to control the plan. The key tasks are those on which the ultimate duration of the project depends, also known as the Critical Chain.
In a Critical Chain Project Management, buffers are used. These buffers are created during the planning to add safety times to tasks within the project so there is a no risk of exceeding the project schedule.
These buffers are split into three types, namely
1. Project Buffer
2. Feeding Buffer
3. Resource Buffer
Project buffer is placed between the schedule of last task in a project and the project completion date. This “safe” duration buffer acts as a contingency for the project activities. Any delay on the critical chain will consume this buffer, but the project completion date will remain unchanged. If any activity in the project is completed early, then the gain would be added to the Project Buffer.
The duration of this buffer is usually 50% of the contingency that was removed from each task estimate. This helps to move uncertainty from each task to the project buffer. Once the project moves into execution phase, this buffer size is fixed and cannot be modified.
Any path of activities merging into the critical chain is called a feeding chain. A feeding buffer protects the critical chain against violations in the feeding chain. Basically feeding buffers are added to the non-critical chains so any delay in non-critical chains does not affect the critical chain.
Like Project Buffer, feeding buffers are placed between the last activity of a feeding chain (non-critical chain) and the activity on the critical chain which will be added to the project baseline schedule. These feeder buffers are calculated the same way as the project buffers.
Resource can be a Person or an equipment. Usually resource buffers are kept alongside the critical chain to make sure they are available when they are required. While the Project Buffer and Project Buffer add “Safe” time so the project is completed within the scheduled time, resource buffer makes sure that the critical resources are available to work on the critical chain activities.