Grün Engineering
Two twin wall boiler flue legs rising into a large header in a brick boiler house
All projects
Flagship project Boiler flues GE4031, GE4033

RAF Marham

New boiler flues for two boiler houses on an RAF station, finished with a witnessed smoke test.

Site
RAF Marham
Town
Marham, East of England
Sector
Defence
Status
B266 complete

Key facts

buildings, B266 and B562
2
header off Ø250 primaries in B266
Ø400
twin wall flues for two 620 kW boilers in B562
Ø300
to install B266, 29 and 30 January 2026
2 days
smoke test on completion
Witnessed

The challenge

Two boiler houses on the station needed new flues. B266 has two 300 kW boilers, B562 two 620 kW boilers.

In B562 the old flue had to come out and be disposed of first.

In B266 the header had to be carried inside the boiler house as well as up the outside wall.

What we did

In B266, Ø250 primaries come off each boiler into a Ø400 header, with three elbows and three tees, then out through the wall to an external riser on three cantilever supports.

We built floor supports and a strut frame to carry the header inside the boiler house.

For B562 the scope was Ø300 twin wall insulated flues, about 6 m of vertical, with the old flue taken out and disposed of.

Both buildings were surveyed and drawn in CAD before any material was ordered.

The result

B266 was installed in two days, 29 and 30 January 2026.

The smoke test on completion was witnessed by the client. The smoke left at the terminal with no visible leakage.

strut channel caps and rod end caps fitted, and closure plates in place where the flue leaves the building.

On site.

6 photographs. Tap a photo to see it larger.

RAF Marham, Marham. B266: both boiler legs rising into the header.
RAF Marham, Marham. External riser on its three cantilever supports.
RAF Marham, Marham. Boiler connection, strut support and the header through the wall.
RAF Marham, Marham. Test point and drain on a boiler leg.
RAF Marham, Marham. Twin wall riser on cantilever brackets.
RAF Marham, Marham. Two risers on brackets up the side of the building, beside the old stack.

Finishing details

The details we leave behind.

  • Strut support under a flue connection

    Strut frame for the header

    Floor supports and a strut frame carry the header inside the boiler house.

  • Test point and drain on a flue

    Test points and drains

    A capped test point and drain on each boiler leg.

  • Riser on cantilever brackets

    Cantilever supports

    Three cantilever supports carry the external riser up the brickwork.

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.

  • Survey and CAD drawingsBoth buildings
  • Job-specific RAMSDecember 2025
  • Progress reportsWith photos, 29 and 30 January 2026
  • Smoke test recordWitnessed by the client, 30 January 2026
  • Certificate of conformityOn completion

Related services

Boiler flues Steelwork and supports Testing and surveys

Short job records: GE4031, GE4033.

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