When the job is on a Thames Water roof next to the Greenwich ferry

We were not asked to quote a standard generator package. We were asked to take old chimneys off the roof of a Thames Water waste treatment plant next to the Greenwich ferry, design the replacements, get the scheme approved, crane two new stacks into position, and make the roof good again.

That invitation only arrived because of the chimney systems we already design, specify and install for our own generator work. On a live Thames Water site you do not get a second chance to look like a general builder with a flue catalogue. You either understand draught, support loads, expansion, weatherproofing and site rules, or you do not get through the gate.

The site, not the brochure

A waste treatment plant is an operational site first. Plant keeps running. Access is controlled. The roof is not a tidy yard with a forklift and a clear turning circle. Next to the Greenwich ferry there is also river traffic, tight approach roads, limited laydown, and a lift that has to be planned around the building, the weather and everyone else still working on site.

Two new chimneys were larger than the people installing them. That is not a figure of speech. Once a stack is on the hook it is a long, awkward load. It does not forgive a sloppy slinging arrangement or a crane that is “probably big enough.”

Logistics: people, plant and the lift

The sequence had to be thought through before anyone cut the first fixing.

Old chimneys came off first. That meant a method for dismantling at height, a safe route off the roof, and a crane programme that could land scrap and send new sections up without blocking the site or leaving the roof open longer than necessary.

The install needed:

• a crane sized and positioned for two tall stacks, not just the weight on a datasheet

• banksmen, slingers and a lift supervisor who treated the roof as a live workplace

• enough hands on the roof to receive, plumb and hold each chimney while it was still on the hook

• a clear exclusion zone below

• a plan for wind. A chimney is a sail the moment it leaves the deck

You do not improvise that on the morning of the lift. You survey, you check ground bearing and outreach, you book the crane for the window you can actually use, and you have a stand-down if the wind makes the load unsafe.

The technical job: design, not just “new pipes”

Replacing the old chimneys was not a like-for-like swap of whatever came off.

The new flues had to be designed as a system: diameter and height for the plant they serve, support steel that takes wind and self-weight back into the structure, joints that can move with heat, and a route that can be maintained. Generator chimney work is the same discipline. A flue that looks neat on a drawing but starves the engine of draught, dumps heat into the roof, or cannot be supported in a storm is not a finished job.

That design then had to be approved. Thames Water do not take a contractor’s word for it. Drawings, calculations, method statements and risk assessments go in. The scheme is reviewed. Only then do you get to put steel and flue on an operational roof.

Approved to work — and staying approved

Getting the design signed off is one thing. Being allowed to work on a Thames Water site is another.

That means their rules, not a generic construction habit. Induction. Competency. Permits to work. Hot-work controls for cutting out the old stacks and for welding the roof back. Lifting plans. RAMS that match what you will actually do, not a template from another job. If the site says stop, you stop. If a permit is not in place, the grinders stay in the van.

We were approved by Thames Water to do the work. We stayed approved by working to their regulations rather than treating them as paperwork to get past the gate.

Craning in, then making the building whole

The two new chimneys went in by crane, one controlled lift at a time, landed onto prepared supports and fixed plumb. Once they were off the hook the job was only half done.

The roof had been opened to get the old systems out and the new ones in. That opening had to be made good. Aluminium roof panels were welded back into place so the building was weather-tight again — not patched with a temporary sheet and a promise. A flue job that leaves a leaking roof is a failed job, whatever the chimney looks like from the ferry.

Why we were asked

Plenty of firms can hire a crane. Fewer can design a chimney system, take an old one apart on a live roof, satisfy Thames Water, lift stacks bigger than the installers, and weld the building back together.

We got this work because that is already what we do for generator exhaust and chimney systems: design, specify, install, and stand behind the result. The Greenwich ferry site was a larger, more public version of the same problem — access, height, approval, lift, and a finished flue that the client can live with.

The power behind your peace of mind.Specialist diesel generator solutions, including the chimney systems we design, specify and install — nationwide.

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