How Exostack works

Exostack EX-series — schematic section Not to scale

Structure

Aluminium exo-skeleton — outside, permanent

Extruded EN AW-6082 T651 sections bolt together in the field, Meccano fashion, with no welding and no hot work. The skeleton carries everything mechanical: its own weight, wind load and the pretension in the guy wires. It never meets the flue gas, so nothing about the exhaust chemistry constrains its specification — which is exactly why it can be aluminium instead of alloy steel, and why it outlives several ducts.

EN AW-6082 T651 Modules under 15 kg M12 stainless, no welds 30+ year design life

Interface

Stainless tensioning cables — duct to skeleton

At every ring level, cables run radially outward from the duct to the skeleton. They are what holds the duct in a true cylinder against internal pressure, wind and thermal cycling — and they do it without bonding the two elements together. Release the cables and the duct comes off the structure as a separate item. That single detail is what makes the duct a replaceable part rather than a demolition job.

Radial, at every ring Stainless, swaged Releasable in the field

Containment

Coated fabric duct — inside, replaceable

A woven base fabric with a fluoropolymer inner coating that meets the gas and a weathering outer coating that meets the sky. It sits inside the skeleton, shielded from impact and carrying no structural load whatsoever — which is why a fabric can do a job that otherwise demands 3 mm of 316L. In the standard specification, PTFE handles the acids and 260 °C continuously; PVDF outside gives 25 years of UV stability.

PTFE inner · 400 g/m² PVDF outer E-glass base · 600 g/m² Swap in 4 hours

Stability

Guy wires — the reason your roof is left alone

Three 6 mm stainless ropes to EN 12385, at 120°, anchored to integrated eyelets at two-thirds height. This is the load path that matters commercially: wind pressure on the stack becomes tension in three wires spread across the roof, instead of a concentrated overturning moment at a base plate. No moment at the base means no secondary steelwork, and that is where €14,000 to €28,000 of a conventional project disappears.

3 × 6 mm · 120° EN 12385, SF 3.0 Turnbuckle pretension Zero base moment

Why the split is the whole invention

A conventional stack asks one wall to be structural, corrosion-proof, weatherproof and permanent at once, so it has to satisfy the worst of all four requirements simultaneously — and you pay for that everywhere, including in the 900 kg you then have to lift and support. Separate the duties and each element gets cheap at its own job. The rest of the system — no crane, no reinforcement, a duct you can renew — follows from that one decision.

Installation sequence

One visit, two engineers, hand tools

The sequence below is for a 7 m × 1,000 mm system on trapezoidal steel sheet. Times are for a two-person crew with a working-at-height ticket and no prior Exostack experience. The clock is cumulative.

0:00start

Set out and anchor the base module

Position the base module — the load-distributing plate and lower skeleton section as one assembly — at the marked location. Mark and drill through the trapezoidal sheet into the purlin or structural member beneath, then fix with M16 stainless anchors at 150 mm minimum embedment. Connect the process exhaust to the low-level inlet port and fit vibration isolators if the application calls for them.

60 min Torque wrench · drill · level 2 engineers

1:00elapsed

Stack and bolt the skeleton sections

Every section is under 15 kg, so each one is carried up by hand through a standard access hatch or stairwell. Align the standardised end flanges with the section below and torque the M12 stainless bolts in a cross pattern to the figure in the manual. Work upward, section by section. Nothing is lifted mechanically at any point in this step — which is the whole reason there is no crane on the schedule.

90 min Torque wrench · ladder No lifting plant

2:30elapsed

Deploy and tension the guy wires

Each of the three assemblies arrives pre-made: 6 mm stainless rope, swaged end fittings and a turnbuckle. Clip them to the integrated eyelets at two-thirds height and run each to its roof anchor. Bring the turnbuckles up in sequence to the specified pretension using the calibrated gauge in the kit. All three must reach equal tension before the duct goes on — you know they have when the skeleton reads plumb on both axes.

60 min Tension gauge · spanners 2 engineers

3:30elapsed

Draw the duct over the skeleton

The duct is supplied rolled in a pre-formed tube. One engineer takes it at the head while the other feeds from below, and it slides down over the standing skeleton. Engage the circumferential tensioning bands at each ring and bring them to torque, then clamp the lower seal gasket at the inlet collar and the upper ring at the head module. The duct pulls itself into a true cylinder as tension comes on — there is no forming or shaping step.

60 min Tensioning tool supplied 2 engineers

4:30done

Inspect, test and issue the record

Walk every flange connection, duct seam and guy termination. Re-check the three guy tensions with the gauge and write the readings down. Test the base connection for gas-tightness. Complete the Exostack installation record — this is the document the Bezirksschornsteinfeger asks for under §14 SchfHwG in Germany, and the equivalent inspection authority elsewhere. The system is then live.

30 min Gas-tightness test Commissioning record issued

Total: 4 to 5 hours, one site visit

Two engineers, standard hand tools, no crane, no welding, no hot work permit and no trade waiting on another trade. A stainless equivalent runs three to five days across two or three visits, with a crane, riggers, a structural contractor and an engineer all needing to be on site at overlapping times.

Taking it down again

The sequence reverses. Release the duct tensioning bands and draw the duct off, slacken and unclip the guys, unbolt the skeleton downward and lift the base anchors. A full demount is a single working day, and the system stores on two Euro-pallets until it is needed at the next location.

Through life

The duct is a wear part. We would rather you planned for that.

Nothing that meets hot acid gas lasts forever, and a supplier who tells you otherwise is selling you a surprise in year twelve. The Exostack duct has a defined service life, a known replacement cost and a four-hour replacement procedure — so it belongs in a maintenance budget rather than a capital one.

The relevant comparison is not against a stack that never needs attention. It is against relining or replacing a rigid stainless stack, which means a crane, a shutdown and a five-figure invoice on someone's unbudgeted week.

See the 20-year cost of ownership

Duct replacement is a planned four-hour job on a live skeleton. The guy wires and structure are not disturbed.
Element	Service life	At end of life
Aluminium exo-skeleton	30+ years	Inspect and re-torque
Guy wires and fittings	15–20 years	Replace rope set
Duct — Option A	8–12 years	€1,175–2,775
Duct — Option B	12–18 years	€1,913–8,200
Duct — Option C	15–20 years	€6,005–11,590
Base anchors and seals	Life of system	Gasket renewal

Annual check, thirty minutes

Verify guy tensions with a gauge, walk the duct for seam or abrasion damage, confirm the base seal and re-torque a sample of flanges. It is a routine rooftop inspection, not a specialist visit, and it goes in the same schedule as your other roof plant.

Where it does not apply

The cases we will turn away

Every engineering system has an envelope, and a supplier who will not name theirs is not worth specifying. If your application sits in one of these, say so early and we will tell you straight rather than stretch the product around it.

Limit 01

Above 260 °C continuous

PTFE tops out at 260 °C continuous and 300 °C peak. Solid-fuel combustion, incinerator primaries and anything running hotter needs a rigid refractory-lined stack. We do not have an answer above that line and will not pretend to.

Limit 02

Sustained positive pressure

The system is classified N1 under EN 1443 — negative pressure operation. Forced-draught applications running consistently above atmospheric need a pressure-rated design and a different conversation.

Limit 03

Nowhere to anchor the guys

The guy wires are the reason your deck needs no reinforcement, so they need three anchor points with modest but real capacity, spread across the roof. A congested plant deck with no usable anchor geometry is a genuine constraint — it is the first thing we check.

Limit 04

Abrasive and hot together

ECTFE handles the abrasive, chemically aggressive streams, but only to 150 °C. Abrasive particulate above that falls between our specifications, and usually resolves upstream with cooling or dilution rather than in the stack.

Limit 05

Carrying anything else

The skeleton is sized for the duct, the wind and the guy pretension. It is not a support structure for cable trays, platforms, sampling gear or antennas. Loads that are not in the calculation do not go on it.

Status, not a limit

Approvals still in flight

DIBt national technical approval and CE marking are in progress, not complete, and the US listings follow. If your project cannot proceed without them in hand today, tell us your programme date and we will give you an honest read on whether we will make it.

Next step

Send us the stream and the roof

Temperature, chemistry, particulate, the height and diameter you need and what the deck is made of. That is enough for an engineer to tell you which duct fits, what it costs installed, and whether the guy geometry works on your roof.

Request a quote → Find the right duct first

ReplyWithin two working days, from an engineer rather than a mailbox

You getA specification recommendation, an indicative installed price and the structural basis behind it

CostNothing, and no obligation

Or emailengineering@exostack.com

Four elements, each doing exactly one job

System elements