I have a task within my project criteria which states: "Purchasing lead-time for the steelwork is estimated at 60-80 days".
What does lead time mean? Do I have to make special considerations for this?
Lead time is the delay between the initiation and execution of a process. For example, the lead time between the placement of an order and delivery of a new car from a manufacturer may be anywhere from 2 weeks to 6 months.
According to the Business Dictionary, Purchasing lead-time is the, "Interval between a decision to purchase an item and its receipt at the warehouse or stores. It is the total of order preparation time, order release time, supplier lead time, shipping or transit time, and receiving, inspection, and put-away time."
Yes, you do have to give special consideration for this. You must factor this lead time in your plan. More importantly, you must note that the Purchasing lead-time doesn't include time to create the design and specification for the steelwork, time to locate and qualify vendors, get quotations and conduct negotiations and make a decision. You should make sure that these tasks are properly incorporated in the plan and time estimates are accounted for.
Ashok gives a great definition for Purchasing lead-time.
Because the term lead time, is a catch-all for a whole load of preceding tasks, its even more important to check how the estimate for its duration came about. A special consideration for you would be to check a little more rigoriously how the estimate has come about. Some questions you may want to consider are:-