Tonnage can tell us how much steel is in a sequence, but it does not tell us how many times the crane has to move or how the crew will install it. Piece count gets us closer, but a fabricated piece is not necessarily a production unit either.
The 3D model may show 100 pieces. That does not mean the erection plan contains 100 picks.
Some members will be erected individually. Several smaller pieces may be rigged together as Christmas-tree iron and installed from one crane pick. Other pieces may be installed as hand iron without passing through the crane-pick cycle at all. A larger assembly may combine several model pieces into one planned lift.
The same 100 model pieces could therefore represent very different operations. Until the installation method is defined, the model gives us quantities but not yet a production plan.
Convert model pieces into installation events.
The first step is to assign each piece to the way it is expected to be installed:
- An individual crane pick.
- Part of a Christmas-tree pick.
- Part of a preassembled or multi-piece lift.
- Hand iron installed without a crane pick.
- A special pick requiring its own planning assumptions.
This converts the raw piece count into planned installation events.
That distinction matters because production happens through those events. A Christmas-tree pick may install several pieces during one crane cycle. Hand iron still consumes labor, but it does not consume a crane cycle. Treating every model object as one pick would misrepresent both the planned crane demand and the expected labor.
Classify the work.
Once the planned installation events are defined, they can be grouped into work classes with similar production characteristics.
A basic classification might begin with weight:
- Extra light.
- Light.
- Standard.
- Heavy.
- Extra heavy.
Weight is only the starting point. Two picks in the same weight range may behave differently because of rigging, geometry, connection requirements, crane position, access or preassembly. A special or complex category may be needed when a pick does not reasonably belong in the standard production classes.
The objective is not to create a perfect classification system. It is to create one that is consistent enough to support a useful planning conversation and improve as actual production is collected.
Attach production values to the work classes.
Production rates should attach to the classified installation events, not to tons in the abstract.
For example, a planning model might assume that a defined raising gang working a defined shift can complete:
- 8 extra-heavy picks per crew-day.
- 12 heavy picks per crew-day.
- 45 extra-light picks per crew-day.
At 45 picks per day, a mix of 30 single-piece picks and 15 two-piece Christmas-tree picks would erect 60 pieces. Count the grouping in the planned picks once. The pick rate still needs to allow for the rigging and connection time of that mix.
Hand iron would need its own production rate or labor allowance because it consumes crew time without becoming a crane pick.
These are not universal rates. They are planning assumptions developed from field knowledge and refined with historical production. Their value comes from making the operating assumptions visible.
Now the model can tell us more than the tonnage and piece count in a sequence. It can tell us how many planned picks of each type the crew is expected to perform and how much non-pick installation work remains.
How much steel does each pick get in?
Illustrative weights and rates, not weight-class boundaries or production standards. Christmas-tree grouping is available for the extra-light example. Adjust the pick rate to allow for rigging and connection time. Labor covers the raising gang only.
- Model pieces
- Installation events
- Work classes
- Production rates
The next step is to convert those classified quantities and production rates into crew-days. Crew-days can then be connected to crew size, work hours and man-hours to develop a resource-loaded duration for each sequence.
The schedule does not begin with spreading tonnage across dates. It begins by defining the work the crew is expected to perform.