Once planned installation events are classified by work class and assigned production rates, the next question is straightforward:
How many crew-days should the sequence require?
A crew-day is one defined crew working one defined shift. A rate of eight picks per crew-day is only useful when the crew size, composition, shift length and expected conditions are also defined.
Convert each work class into crew-days.
Suppose a sequence contains:
- 8 extra-heavy picks
- 24 heavy picks
- 90 extra-light picks
The planning rates are:
- 8 extra-heavy picks per crew-day
- 12 heavy picks per crew-day
- 45 extra-light picks per crew-day
Each work class can be converted into the crew-days required to complete it:
Planned picks ÷ picks per crew-day
The base production model gives us five crew-days. Hand iron and other work outside the crane-pick cycle still needs its own production rate or labor allowance so it is not buried inside the crane-pick rate.
Add the crew-days for all work classes to get the total.
This is the bridge between the information in the model and the duration in the schedule.
Convert crew-days into planned man-hours.
Multiply the crew size by the shift length to get man-hours per crew-day. Then multiply by the crew-days required for the sequence.
The sequence now has a visible operating basis: work class, production rate, crew definition, required crew-days, planned man-hours and duration.
The tonnage and planned picks in the work package can then be connected back to the labor plan.
Both labor rates use the same raising-gang hours, so MH/ton = MH/pick × picks/ton. Total-project MH/ton also includes the follow-up and support labor. Keep that scope explicit when comparing the plan with the estimate or actual performance.
This is an important distinction. MH/ton does not build the schedule. The classified work and its expected production rates build the required crew-days. Planned MH and MH/ton are outcomes of that operating plan.
Build the sequence from crew-days
What if the calculation and the superintendent’s schedule disagree?
The superintendent typically develops the erection schedule sequence by sequence using the drawings, model and field judgment. The production model supports that schedule by breaking the durations into measurable assumptions.
On one project, my initial calculations showed that we could erect several sequences faster than the superintendent had scheduled. When we compared the two and talked through the work, he explained how restricted access would slow the operation. I hadn’t accounted for that, and my production rates were too optimistic.
The same restrictions affected several sequences, so I updated the model with a duration multiplier to account for the extra time. His experience helped me see what the calculations were missing and bring the model closer to the conditions the crew would actually face.
The process can also work in reverse. A scheduled duration, crew size and work package quantity can be used to calculate the production rates implied by the superintendent’s plan. Those implied rates can then be compared with similar work or historical production.
The objective is not to replace field judgment with a formula. It is to give that judgment a measurable structure.
Would doubling the crew cut the duration in half?
Crew-days are not generic labor that can be divided among any number of people. If one crew needs ten days, doubling the crew does not automatically reduce the duration to five. The crane, connection process, access, deliveries or another part of the operation may still control production. Adding people behind the same constraint can increase MH/pick without increasing picks per day.
A second crew can reduce duration only when the work can be divided into independent fronts with the required cranes, access and supporting resources. The production rate must remain connected to the crew and operating conditions used to establish it.
Crew-days describe the work expected from a defined production unit without pretending that manpower and duration are interchangeable.
Build the duration from the operation.
At the end of this step, each work package has a production-based duration and planned labor demand:
- Classified work
- Production rates
- Crew-days
- Planned MH and duration
The value is not the arithmetic by itself. It is that the assumptions behind the duration can be seen, discussed and updated.
Once each sequence has been developed this way, the work packages can be placed on the project schedule. That is where the individual durations generate the manpower and crane loads for a complete resource-loaded erection schedule.