Grün Engineering
Three twin wall boiler flues with steel support frames on the roof
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Flagship project Boiler flues GE2594

DVLA

Three Ø500 flues for three 2.5 MW boilers, held on a tied roof frame that stands on rubber feet.

Site
DVLA
Town
Swansea, Wales
Sector
Government estate
Status
Complete

Key facts

boilers, 2.5 MW each
3
twin wall insulated, 550 OD
Ø500
of flue, 12.3 m per boiler
36.9 m
above the roof
4.3 m
of galvanised channel in three tied cages
120 m
to rebuild the roof restraint
3 days

The challenge

Three refurbished boilers needed replacement flues, and the boiler house had to keep running.

Nothing could go through the roof to hold the flues up.

In November only one flue could be extended, because the other two boilers were running.

What we did

Each flue stands in a cage of 41 x 41 mm galvanised channel. The three cages are tied with rails and bracing so they work as one frame.

The frame sits on rubber feet, so there are no roof penetrations.

Each flue has a condensate outlet and an inspection tee at its base.

Our technical note gave the structural engineer the base loads and brace forces in one document. The other two flues were done in December, in heat-proof visor and gloves.

The result

The roof restraint was redesigned and rebuilt in three days, 10 to 12 December 2025.

Smoke tested on 12 December 2025, with no visible leakage, and certified.

The boiler house kept running throughout.

On site.

7 photographs. Tap a photo to see it larger.

DVLA, Swansea. The three flues in their frames on the roof.
DVLA, Swansea. A terminal in its braced frame, with the office tower behind.
DVLA, Swansea. The three flues held in galvanised steel frames.
DVLA, Swansea. Steel frame around one of the flues.
DVLA, Swansea. Braced frame around two flues, close up.
DVLA, Swansea. Channel frame standing on rubber feet.
DVLA, Swansea. Storm collar and weathering plate at the roof, with end caps on the channel.

Finishing details

The details we leave behind.

  • Channel frame on rubber feet

    No roof penetrations

    The frame stands on rubber feet. Nothing goes through the roof.

  • Braced channel frame around two flues

    Braces and split bands

    Corner braces and split-band restraints tie each flue into its cage.

  • Storm collar and weathering plate

    Weathering at the roof

    Storm collar and weathering plate where each flue meets the roof, with end caps on the channel.

Handover

What the client got.

The documents on record for this job. Handover documents normally go into the customer's project folder before the engineers get home.

  • Frame drawingDrawing 0000-001, 9 December 2025
  • Technical note for the structural engineerBase loads and brace forces, 15 December 2025
  • Smoke test certificate12 December 2025
  • Certificate of conformityDecember 2025
  • Progress reports21 November and 12 December 2025

Related services

Boiler flues Steelwork and supports Testing and surveys Design and calculations

Short job records: GE2594.

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