Shipping a silo into Korea: bolted flat-pack or welded sections
You have a silo to deliver to a site in Korea, and the drawing office is waiting to hear whether to detail it as bolted panels or as welded shell sections. That decision looks like a fabrication choice. It is not. It is set by the last few kilometres of road, by the gate the trailer has to turn into, and by the crane that can stand next to the foundation on the day the steel arrives.
Fix the form before anyone has looked at those three things and you learn the answer at the worst moment: the pieces are on the water, the largest one is 3.4 m across, and the road permit for the final leg comes back with conditions that move the delivery by weeks. Nothing about the silo was wrong. The order of the decisions was.
Four things to ask the receiving site before detailing
The information that decides the form sits with the buyer, not with you, and nobody sends it unprompted. Ask for four things in writing.
First, the clear width and height at the tightest point of the approach, from the public road to the foundation — including the plant gate, any underpass, pipe racks and overhead lines. Second, the laydown area next to the foundation: how much flat ground is available for pre-assembly, and for how long. Third, where a crane can be set up, what it can be supported on, and what class of machine is realistically available in that region on your window. Fourth, whether the plant will be running when you arrive, because that governs permits and working hours more than anything else on the list.
A site plan and a few photographs of the approach answer most of it. What you do with the answers is the rest of this article.
What fits in a box, and what stops being a box problem
A 40 ft dry container gives roughly 12.03 m x 2.35 m x 2.39 m inside; the high-cube version has the same footprint with about 2.70 m of height. Bolted silos are detailed against those numbers. Curved panels, ring segments, stiffeners, ladder sections and the hopper plates stack flat, and the whole silo leaves the shop inside standard boxes. The sea leg is ordinary freight.
A welded silo does not miss that envelope by a little. A shell can 3.4 m in diameter is over the internal width before you add the cradle it sits in. It moves as out of gauge cargo — flat rack, open top or breakbulk — and the sea leg handles that routinely, at a price and with more handling. The road leg is where the same piece stops being routine.
That is the part worth internalising. Ocean freight rarely decides the form. The road behind the port does.
Korean road limits are a permit threshold, not a wall
On Korean roads a movement is treated as a restricted vehicle load once it exceeds any one of these: 2.5 m wide, 4.0 m high — 4.2 m on sections the road authority has designated as suitable — 16.7 m long, 10 t on an axle, or 40 t gross. Past any single one of them the movement needs an oversize-load permit from the road authority, filed at the point of departure, and where the route crosses more than one authority those authorities consult each other before it is issued. Published handling is within five days, or within ten when that consultation is needed. Confirm the current figures and handling times for your own route before you plan a schedule around them.
Two consequences catch exporters out. The permit is issued against a named vehicle on a named route. Swapping the truck is a change application on the same route; taking a different road — a new port of entry, a detour around works — starts the application again from the beginning. And the permit can come back with conditions attached — the hours during which you may move, an escort vehicle — and those conditions, not the driving distance, set the delivery date.
The arithmetic is unforgiving in one direction. That 3.4 m can, lying on a low-bed deck roughly a metre off the ground, stands around 4.4 m to the crown. Every underpass, footbridge and overhead line on the route becomes something a transport contractor surveys, not something anyone assumes.
Reading your site conditions against the two forms
| Condition at the receiving site | What it usually means | How to confirm | If you read it wrong |
|---|---|---|---|
| Tightest point on the approach is under about 3 m clear | Welded cans of that diameter cannot reach the foundation; bolted panels can be trucked in normally | Site plan plus a route survey by the Korean transport contractor, not a map measurement | The trailer stops short, the pieces are set down in a yard and re-handled, and a second crane appears in the cost sheet |
| Crane capacity at the required radius is limited | Favours pieces the available machine can lift — bolted panels, or a welded shell split into more cans | Lift study from the lifting contractor with radius, ground bearing and the crane actually available on your dates | The lift is refused on the day and the pieces sit on the site while a larger machine is found |
| Plant is running and hot work is permit-controlled | Site welding has to be scheduled around production; bolted assembly avoids most of that | Ask the plant for its hot work rules and the hours it will release | The erection crew is on site and idle, waiting for permits that are issued a few hours a day |
| The silo may be relocated later | Bolted can be dismantled and re-erected; welded has to be cut | Ask the end user whether the location is permanent or tied to a construction phase | A structure that has to be scrapped rather than moved when the site changes |
| Fine powder stored, tightness matters | The joints carry the risk on the bolted form — sealant specification and bolt torque are part of the design, not site detail | Confirm the stored material, its moisture and the fill method, then the joint detail against them | Dust at a seam on first fill, on a joint that is now 20 m up |
What each form asks of the site once the steel is there
Bolted assembly is a bolting job, and it is only as good as the discipline applied to it: torque values per joint, sealant laid in the sequence the maker specifies, and a torque record if the buyer asks for one. Send spare bolts and sealant with the shipment. A missing bag of the right grade stops a crew that costs considerably more per day than the bolts do, and the replacements are not on a shelf nearby.
Welded assembly asks for different things: welders qualified to the procedure, access at height that the site will actually approve — scaffold, or an aerial work platform with ground firm enough to stand it on — power at the base, and weather that stays within the limits the procedure allows. If your specification calls for non-destructive testing of the site joints, the inspector has to be on site inside the same window, which in practice means booking that person before the ship is booked.
Inside a running plant the difference sharpens. On-site welding is permit-controlled work with a fire watch and agreed hours, and it competes with everything else the plant wants to do that week. That, more than transport cost, is what pushes existing plants towards the bolted form. If the silo is already standing in Korea and the question is a safety package rather than a delivery, that is a different job — see retrofitting silo protection on a running plant.
Where the price actually changes
The steel does not move much between the two forms. Days do. Number of lifts, the class of crane and how many days it stands, the road permit and any escort, port handling for out-of-gauge pieces, temporary works, and the erection crew's time on site — that is where the difference lands.
Flat-pack silos are marketed with a logistics saving as the headline. Whether that saving appears on your job depends on whether the route was going to need a permit and a larger machine in the first place. On a coastal site with a straight approach and a crane already standing for other work, the welded form can land cheaper and finish sooner, because there are far fewer joints to make and seal. On an inland site inside a running plant, the same comparison usually goes the other way.
The related trap is commercial. Quoting ex works and leaving the inland leg to the buyer means the road leg gets priced after the form is frozen, which is the wrong order — the survey that should have informed the design happens after the design is closed. Getting the route and the lift checked while the form is still open costs a few days at the front, and that is what delivery execution into a Korean site is for.
The lift window becomes the next thing that jams
Settle the form and the constraint moves one step down the line, to the day the crane can stand. Machines in the class a silo needs are booked well ahead, and their availability is not evenly spread across the country — a site far from the main industrial belts has fewer options and less tolerance for a slipped vessel.
The foundation has to be ready to receive on that same day: anchor bolts set to the template, the base ring inside the flatness the erector works to, and the concrete at the strength the design requires before anything is stood on it. That handover — civil contractor finished, erection crew arriving — sits between two scopes and belongs to neither, which is where schedules usually lose their first two weeks. Part 2 covers it: who receives and erects a silo on a Korean plant site.
Send the diameter, overall height, section weights and the delivery address to our logistics team and you get back the route, where a permit is required, and whether the lift is feasible on the date you are holding.