Field notes

Mining Conveyor Structures: Fabricating Stringers, Gantries and Transfer Towers for Export

Published 26 September 2026

Conveyor structure is the most repetitive heavy fabrication in a mine. A single overland conveyor can run to thousands of stringer modules, hundreds of idler frames and a dozen transfer towers, and every one of them has to bolt to the next one in a different country from where it was welded.

That repetition is what makes conveyor steel a good fit for export fabrication, and also what makes it unforgiving. A dimensional error in one stringer is a nuisance. The same error in four hundred identical stringers is a site stoppage. This guide covers how the structure is broken into fabrication modules, what the coating decision changes and what a buyer needs on the drawing and in the contract. The mining equipment frames page covers the related crusher and screen structures.

The pieces of a conveyor structure

A typical belt conveyor package breaks into:

Element	Typical construction	Fabrication note
Stringers	Channel or lipped channel pairs with cross bracing, in 3 to 6 m modules	Highest repetition, jig-built
Idler frames	Pressed or welded brackets bolted to stringers	Often supplied by the idler vendor
Trestles and bents	Welded H-frames or braced towers	Height varies along the route
Gantries	Truss or box girder spans between trestles	Largest single pieces
Transfer towers	Braced steel frames with platforms and chutes	Most complex, most site interfaces
Drive and take-up frames	Heavy plate weldments, machined for pulley bearings	Closest to machine base work
Chutes and hoppers	Plate shells with bolt-on wear liners	Liner detailing decides service life

Each of these has a different fabrication logic. Stringers are a production run. Drive frames are one-off heavy weldments with machining. Transfer towers are a structural steel job with a lot of interfaces. A single export package usually needs all three kinds of shop capability.

Design for modular shipping

Conveyor steel is designed around the container or flat rack from the start. Good practice:

Stringer modules sized to nest. Channels nest inside each other. A module length that fits a 40 ft container with room for dunnage cuts freight cost more than any other decision.
Bolted splices, never welded on site. Every site joint is bolted. Holes are drilled or punched in a jig to a common template so that any module bolts to any other.
Gantries in sections. A 30 m gantry ships as three 10 m sections with bolted splice plates and a documented camber. The camber has to be measured and marked before it leaves the shop.
Trestles as flat-pack frames. Legs, bracing and cap beams as loose pieces with match-marked connections, or as welded H-frames if they fit.
Transfer towers as bolted columns and braced panels, with the platforms, handrails and stair stringers packed as numbered kits.

The out-of-gauge shipping guide covers what happens when a piece cannot be made to fit.

Hole accuracy is the whole job

Bolted modular steel lives or dies on hole position. If the stringer splice holes are within a millimetre of the template, site erection is a bolt-up. If they are not, it is a reaming and drilling job at height, in the dust, with the schedule running.

Buyers usually specify:

Hole diameter and position tolerance per the structural code, typically clearance holes at bolt diameter plus 2 mm, with position within 1 mm of nominal for splices.
Drilling by CNC line or from a numbered template, not marked out by hand.
Trial assembly of a representative run in the shop, photographed and measured, before the production run starts.
A trial fit of each gantry section to its neighbour before shipping, with the match marks recorded.

A trial assembly costs a day in the shop. It saves a week on site.

Galvanising versus paint

Most mining conveyor steel is hot-dip galvanised to ISO 1461 or ASTM A123. It is cheaper than a multi-coat paint system over the life of the structure, it tolerates handling damage and it does not need touch-up at every bolted splice. The trade-offs:

Bath size. The largest piece has to fit the zinc bath. Galvanisers publish their bath dimensions; the design has to respect them, and double-dipping has consequences for distortion.
Venting and drainage. Closed sections need vent and drain holes so that the zinc can flow in and out. Those holes are a design detail, not an afterthought.
Distortion. Asymmetric weldments and thin plates move in the bath. Symmetric design and balanced welding limit it.
Bolted joints. Galvanised faying surfaces in slip-critical connections have a lower slip factor than blasted steel. The connection design has to allow for it.

Where paint is specified, mine sites generally call for an ISO 12944 C4 or C5 system over a Sa 2½ blast. Paint makes sense for the heavy drive frames and for anything that will not fit a bath. The surface finish guide lays out both systems.

Chutes and wear liners

Transfer chutes and hoppers carry the abrasion. The structural shell is ordinary plate; the wear is taken by bolt-on liners in abrasion-resistant plate, ceramic or polyurethane. The details that matter:

Liner plates sized to be lifted by one person, or with lifting holes if not.
Bolt patterns that let a liner be swapped from outside the chute where possible.
Flow angles and impact zones on the drawing, so the shop knows where the heavy liner goes.
Countersunk liner bolts where the flow would catch a bolt head.

A chute that is cheap to reline is worth more to the mine than a chute that is cheap to buy.

Drive frames: where it becomes machine base work

Drive and take-up frames carry pulleys, bearings, gearboxes and motors, and they need machined bearing seats and mounting pads. That puts them in the same category as the crusher bases covered elsewhere on this site: heavy plate weldments, stress relieved and machined in one setup, with a flatness tolerance and an inspection report. Not every stringer shop can do them, and the package often needs to be split between a structural shop and a machine base shop.

Documentation for an export package

A conveyor package arrives complete when the paperwork does. Ask for:

Material certificates traced to heat, per piece mark.
Galvanising or coating certificates with thickness readings.
The trial assembly report with photographs and measurements.
A piece list with mark numbers, weights and container or crate numbers.
Match-mark drawings for gantry sections and towers.
Bolt schedules per connection, with the bolts shipped in labelled kits.
Lifting points and weights marked on every piece over a size the site rigging crew cannot handle by hand.

Sending a conveyor package out for quotes

Conveyor steel is usually quoted from a bill of materials and a set of typical drawings rather than every detail drawing. Send what you have through the RFQ form, with the module count, the longest single piece, the coating spec and the destination port. Within 24 business hours we tell you which shops in the network fit the run, and up to three of them quote you directly.