Steel erection works like a factory, with one important difference.
In a traditional factory, material moves through a series of fixed workstations until a finished product comes out the other end. On a steel project, the product stays in place while the workstations move through the building.
The crane, raising gang and supporting crews advance from sequence to sequence. Each sequence moves through erection, plumb and bolt, welding, decking, detail, inspection and closeout.
Move the factory through the building
Advance the day. The raising gang moves first; follow-on crews need completed work and room to follow.
Press Play or drag the day slider to follow the crews.
Illustrative crew-day example. Each crew works one area at a time; stages start after the prior stage finishes. Decking and detail are combined here to keep the motion readable.
The raising gang is the most visible workstation.
It produces the picks, pieces and tonnage we have used to build our sequence durations and time-phase the work. It also has the crane, and let’s be honest, cranes are just cool to watch working.
That visibility makes it natural to treat the raising gang as the entire production operation. Its pace matters, and it gives the rest of the operation something to plan around. But hanging iron is only one stage in the factory.
A sequence is not complete when the last piece comes off the hook. The steel still has to move through every operation that follows.
The goal is not just to put steel in the air. The goal is to move completed work through the entire system.
Translate the factory to the erection operation.
The comparison is not perfect, but the terminology helps describe what is happening:
| Manufacturing term | Steel erection equivalent |
|---|---|
| Raw material | Fabricated and delivered steel |
| Production batch | Erection sequence or work package |
| Workstations | Erection, plumb and bolt, welding, decking, and detail |
| Material handling | Delivery, shakeout, rigging and hoisting |
| Work in progress | Erected but incomplete sequences |
| Quality control | Survey, inspection, punch and verification |
| Finished product | Completed and released work package |
| Production line | The path the erection operation follows through the project |
The major difference is that the operating conditions change as the factory moves. Access changes. Pick radii change. Connection details change. Deliveries and crane configurations change. The production system has to travel while continuing to produce.
Erection establishes demand on the rest of the system.
The erection schedule gives the supporting operations their required pace.
If the raising gang completes a sequence every seven days, the crews following it must collectively be capable of processing that work at approximately the same rate. Otherwise, incomplete work begins accumulating between operations.
A fast raising gang can create the appearance of strong production while plumb and bolt, welding, decking or detail falls farther behind.
The tonnage is in the air. The picks are complete. The sequence is still not finished.
That unfinished work is work in progress.
The Assembly Yard exercise makes the same flow question tangible: add boxes in the yard and see whether the erection crane actually finishes sooner.
Some work in progress is necessary. The following crews need enough available work to remain productive, and every operation needs some separation from the one ahead of it.
Too much work in progress creates a different problem. It ties up access, leaves multiple sequences partially complete, increases coordination demands and delays turnover. The project may look busy without producing completed work any faster.
Local production and system throughput are not necessarily the same thing.
Measure the movement of completed work.
Throughput describes the rate at which the entire system produces completed work.
For the raising gang, we may measure tons, picks and erected pieces. Those measures tell us how work is moving through one important operation.
At the project level, we also need to know how work is moving from erection through completion.
That can mean tracking when each sequence is:
- Delivered / unloaded
- Erected
- Plumbed and bolted
- Welded
- Decked
- Punched
- Released or turned over
This creates a production history for the entire erection operation instead of only the crane operation.
If sequences are being erected faster than they are being completed, the gap becomes visible. If the supporting operations are waiting because the raising gang cannot provide enough work, that becomes visible too.
The objective is not to maximize the output of every crew independently. It is to keep the entire production system moving at a rate that supports the project goal.
Follow the factory through the building.
The schedule from the previous note time-phased each sequence and generated the expected crane and manpower loads.
The next step is to define what it means for a sequence to pass through each production stage.
Delivered, erected, plumbed and bolted, welded, decked, punched and released must each have an objective completion gate. Otherwise, the production history depends on interpretation.
Before we can see where work is accumulating or which operation is setting the pace, the team needs consistent rules for claiming completed work.