Critical Chain Project Management
People, professionally engaged in project management, have to know as many techniques, methodologies, and solutions as possible. One of the widespread ways to analyze projects is Critical Chain Project Management (CCPM). What is it? Let’s together figure it out.
What is critical chain project management?
This is a critical technique to plan and manage plans where much attention is paid to resources and resource management, risks and uncertainties. It is built on principles of keeping them leveled and where start dates are supposed to be flexible. This is what makes the difference between this method and more traditional ones such as CPM in project management and PERT.
This method that in general originates from Theory of Constraints notions was introduced in the book with the title Critical Chain. It was written in 1997 by Eliyahu Moshe Goldratt, the famous business guru of Israeli origin.
Critical Chain by Eliyahu Goldratt
Actually, the author originated many notions that are familiar to people engaged in plans scheduling. They include already mentioned the Theory of Constraints (or TOC for short), Drum-Buffer-Rope, the Thinking Processes and some others. He also devoted himself to writing business novels where he described ways of applying knowledge to business processes.
Why did Goldratt introduce the Critical method?
His introduction was a sort of response to problems that existed in projects. They were typical ones and included extended duration of plans, missed deadlines, poor performance, increased costs, etc. In general, tasks were not completed within budget and on time. Peers immediately recognized new ideas and highly valued the critical chain Goldratt proposed.
This is commonly recognized as the longest group of dependent tasks. The word dependent here refers only to resources. This is the point of difference between critical chain method and critical path method. What are those key differences?
When we speak about the critical path, it is implied that resources regardless of their nature (people, equipment, money) are always available. This is the problematic point of the approach as it is not always the case. Moreover, according to it, any delay in a certain activity impacts on other tasks what leads to a project delay.
Critical chain method does not rely primarily on estimates. They are to be shortened here by 50% of a normal duration. Such an approach allows managers to eliminate uncertainties and rely on new notions – buffers – that serve as strategic points. Safety buffers are widely used here to level down risks and ensure stability of a plan.
The following buffers are distinguished.
Project buffer that is put at the end in between the last task and the date of completion. It helps to keep the completion date the same even if there are some delays. Those delays consume buffer time what allows protecting the completion date.
Feeding buffer is added between last assignments in different groups – non-critical (that also can be called feeding paths) and critical ones. This buffer is needed to protect the critical one from any delays on a feeding path.
Resource buffer is used on the critical dependent group. They ensure that resources are available in case they are needed.
Critical chain project management example
Let’s take a look at a simple example where all described above buffers present.
Tasks that go along a parallel line from Start to End form the Critical chain.
To support this approach, special critical chain project management software is needed. It can accompany other popular tools such as GanttPRO that help to make timeline charts for project scheduling.
Have you ever used the described critical method in your projects? What advantages and disadvantages can you distinguish in it? Please, share your experience with us!