Report - Portwood gas works, Stockport – Summer 2018 / Winter 2019

[FreshFingers]

Living in Stockport and passing time as kids, we often did what kids did and played by the riverbank of the Goyt. A prominent feature that we always played near were these towers containing gas. At the time they were part of the landscape and given no thought at all, and certainly not to the land they occupied in general. It's only now, looking back with a bit more understanding and respect for Stockport’s choking and poisoning past, do I think it's important to document its industrial heritage. Stockport Historical Investigation Team does.

I’m not sure the following report follows a standard 28DL format, and I hope it’s not a slog to get through, but I do feel it’s important to at least document our local heritage. So maybe this is a bit more of a historical walk through in a chronological sense with bits of ‘The report’ thrown in for good measure.

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Always on the lookout for something new, Alley had read a letter giving notice of projected works due to be completed at the gas works. Following a message, we met not long after for a casual look. Sadly, after being ushered into a corner of the fencing and having demonstrated the effect of a pie or two, we decided to leave it for a while.

Sometime later
In the company of Alley and SLG, a second visit was underway. This time we took a much different route. With temperatures unusually high for a late evening, wearing shorts was a nice relief. Avoiding nettles like seasoned explorers, we dropped down to the bank of the river and began to wade over to the other side of the river.

Taking in some bonus shots of the vertical sandstone faces which most of Stockport is built on, we admired a nice little tunnel, possibly an outlet for the boiler house and the hidden footings of the demolished Vernon Mill.

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Waders placed to one side and regretting the choice of leg wear within a few steps, we spent a good 30 to 40 minutes trawling the river-bank looking for a nice easy way in. Eventually finding a suitable tree to scale up, the explorers quick reference handbook was referred to - a good look around (tick) bags under (tick) rip another t-shirt (tick)…and we're in.

Having decided to start at the far point of the site, once there, we zig-zagged back to the entry point taking photos as we did. A good 30 minutes poking around was had.

For years, visiting the Goyt, I'd always used the 'big pipe' crossing the river as a visual reference point, but it wasn't until Alley was climbing a valve gantry that it became obvious to us that it was a supply line out from the exiting modernised network feeding an area to the south.

Governor

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The flow of gas sounded mesmerising; the flow was heard loudly as gas pressure being regulated through the governor sounded like air passing through the lungs of a giant.

Gasometers have been seen many times on this forum, so there's nothing to tell on them from an exploration point of view, but I thought I’d offer a bit of detail on the basics of a coal gas plant. Although it was nice to see them up close after all these years, inspect a bit of engineering and a general loiter, we left in the knowledge that more of Stockport was to be turned into yet another carpark...goodbye industry.

Chronology of gas works in Stockport
1820 The first gas production site in Stockport erected in Millgate with a capital of £10,000.

1821 Committee of the Stockport Gas Light Company commence laying pipes.

1826 – 1830 Heaton Lane gas works was in operation and in competition with the Millgate site. It had two gas holders, a coal store and a retort house.

1839 Passing of the Improvement Act empowered Stockport Gas Corporation to purchase both Millgate and Heaton Lane sites. £21,493 10s 0d bought both sites.

1876 Extensions to the Heaton Lane site were deemed not viable to meet future demand. A new site in Portwood was chosen for the erection of the latest works.

1878 Gas making at Portwood commenced.

1891 Production capacity at Portwood site at 750,000 cubic feet per day.

1892 Millgate gas works site closed.

1900 Electricity power station operating on the old Millgate gas works site.

1907 Gas manufacturing at Heaton Lane stopped. Gasometers in use for storage only.

1928 Production capacity at Portwood site reaches 6,500,000 cubic feet per day.

1929 Heaton Lane storage station stopped.

1931 Waterless Gasholder number 3 constructed at Portwood.

1931 – 1932 Possible rebuilds of gas holders 1 and 2 at Portwood.

1969 Old retort house demolished.

1988 Gas holder number 3 dismantled.

2003 Last aerial view showing the gasometers in the raised position.

2019 Removal of gas holders 2 & 3.


General
Industrial Heritage often lies dormant, hidden behind nondescript doorways, but can be viewed so often that it becomes part of the normal skyline to the casual passer-by.

Falling victim to this site by my underestimation of the importance and impact it had on the lives of so many local people in the early nineteenth century, it justifies more recent documentation.

Location of earlier gas works (Heaton Lane & Millgate)

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As of summer 2018, Portwood gas works was a shadow of its former self. A victim of modernisation, the only reminder of the past being two rusting crowns fenced away behind a retail park. Standing in the centre of the site, imagining the thudding of solid-wheeled trucks returning from the short journey from Portwood coal sidings, the clash of mechanisation during loading of the retort hoppers and the roar from the furnaces must have been an experience.

Hissing, bubbling, steaming, noxious processes attacking the senses from all angles. Smoke and falling soot were an issue for the house-proud wife. A local lady told us that when she walked to school in her white woollen coat it would be grey by the time she arrived. It is mentioned that washdays were governed by the operating times of the retorts.

Hidden wonders
When operating at full potential, the utilised land consumed an area of approximately 12.5 acres from Great Portwood Street, southwards to the bank of the River Goyt, the bend in said river and east towards Palmer Mill.

Aerial images Portwood gas works

Site development at Portwood

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Prior to final demolition, one could have been excused for thinking the site was clear, but keeping a low profile were two four-stage gas holders, neatly nested within each other like Matryoshka dolls. Approaching the holders gives an idea of the immense void inside. The rusting crown inviting someone to walk over the top of it, a person braver than myself!

 

[FreshFingers]

Land occupation
The later gas works were situated on the backfilled Portwood reservoir used by Peter Marsland to supply the Park Mills further downstream. The chosen site would have been backfilled sometime between 1851 & 1873.

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Prior to the Portwood site, there were already small-scale gas works operating in mills that required gas for operations, an example being Park Mills. Two larger commercial sites had operated prior to Portwood. The first was located west of the bridge over the Goyt, an area called Millgate during the early 1820s. Note, the above OS map names the river as Mersey, but this section is now known as the Goyt. The Electricity works buildings occupied the land soon after the gas works would relocate.

Only a few years later, a gas production site was operating in Heaton Mersey, where subsequently the tram station was built, and where the present-day multi-storey car park stands.

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Production carried on at both sites for some years, with extensions being made to Heaton Lane during 1865. The insatiable demand for gas in 1876 required further extensions, but this would be hampered by the proximity of other buildings and services, so a new site was sourced in expectation that demand would overcome production.

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The chosen site was Portwood and was in operation by 1878. The entrance to the gas works was from Great Portwood Street, flanked by a gas laboratory, offices and a showroom to the left, and single-storey workshops to the right with ornamental ironwork. A re-purposed section of the ironwork can still be seen today.

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An increase in the uptake of gas and associated equipment during the early 1900s developed the need for a three-story distribution depot. It was suitably located on Marsland Street, alongside the Tiviot Dale railway line and opposite the gas works at Great Portwood Street. The basement and ground floor were used for storage of materials, the first floor for cleaning and overhauling of equipment (cookers, grills etc) and the second floor was where gas meters would be tested prior to and after repair. External land allowed movement of lorries and a Scotch Derrick handler to load, unload and position stock.

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Presumably low wages being the cause of the workers strike during 1912, Mr S Meunier, the gas engineer and manager of the Stockport Corporation, reported that the three-day strike stopped production of no less than 8 million cubic feet of gas, amounting to £800. The dependence of the gas supply was not felt until the strike as it left the whole area without heating, not to mention a high proportion of lighting. Council workers would distribute hot soup to those in need, primarily those with young children or the infirm.

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Gas production continued during and post war years, but a slow death was to become of town gas production with the discovery of natural gas located deep below the seabed of the North Sea. It was demonstrated that liquid natural gas could be transported safely and efficiently.

A Fuel Policy White Paper formed in 1967 created a surge in demand for this new type of gas, resulting in hundreds of miles of high pressure pipes being laid, a national distribution grid, and at a cost of over £100,000,000, the decommissioning of coal gas plants and conversion of customers appliances so that they would be able to burn the newer type of gas.

The wasteland created after the demolition of the gas work buildings were redeveloped during the late 90s for retail use. Pre-build ground water testing showed heavy metals and organic contamination with Benzene and Toluene resulting in the need for reactive clay barriers to be dug along the riverbank.

Plant Equipment Information

Boiler House
The site used two methods to generate steam for its numerous engines that would power pumps, blowers and general machinery. It also created the steam for the production of Water Gas.

First method - Four coke-fired, force-draught Lancashire boilers giving rise to 16,000 lbs per hour. The coke used to fuel the boilers was the processed coal from the Retorts.

Second method - Heating the water using the hot waste gases leaving the vertical retorts which would be rising (via convection and heat) through a system of pipework within the flow.

The latter method was over 250% more efficient.

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Retort House
This building is where coal, most likely pulverised to increase yield, would be fed into the Retorts from over-head hoppers by gravity. The coal would be heated to temperatures in excess of 1000ﾟC for approximately 12 hours. This process would release the gas. The spent coal is now known as coke. At peak production, Portwood was producing a combined daily output of 9,000,000 cubic feet of gas. A total of six bays, each bay comprising of twelve vertical Woodall-Duckham Retorts heated either upwardly (vertical retorts) or lambently (inclined retorts).

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Coke recovery and storage
Once the coal had been processed in the Retorts, the coke was fed by band conveyors to two vibrating double-deck Pegson screens which could process approximately 50 tons per hour. A second 30 ton per hours screen was located external to the Retort House, but this was later upgraded to the Pegson type.

Two travelling cranes mounted on a gantry allowed the stacking of coke within a 50-foot reach and a 3000lb load in the coke yard.

Coke that wasn’t destined to be recycled back into the furnaces could be bought each Saturday morning. Prior to the second world war, taking a sack, it would be filled with 100lbs of coke. If the sack wasn’t too large, it was just filled, but during the times of rationing, it was strictly limited to 50lbs.

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Carburetted Water Gas Plant – (C.W.G)
The coke was used to produce an additional gas called Water Gas. This was done by alternately blowing steam and air through the superheated coke. After a few cycles, the superheated pressurised hydrogen and carbon monoxide mix was fed through a brick chamber whilst a fine mist of oil would be sprayed into the stream (carburetted). The superheated air would cause the oil to ‘crack’ and release gas. The site initially comprised of one hand-operated Humphreys and Glasgow plant, originally of 500,000 cubic feet per day, but later modified with a ‘back-run’ process to increase capacity up to 800,000 cubic feet per day.

To increase capacity, the installation of a fully automated Humphreys and Glasgow plant, complete with condensers, blowers and ancillary equipment was installed. Incorporating an annular and waste heat boiler, a turbine driven blower, supplemented by an electric motor, production could be raised to 3,000,000 cubic feet per day.

The resultant gas was stored in two steel tanks with a total capacity of 103,680 gallons.

Water Supply
Water for the boilers and amenities was provided by a borehole driven into the site grounds. Two centrifugal pumps also drew water from the River Goyt and this was then stored in an overhead tank storing 12,000 gallons.

Condensing and Purification Plant
Both Coal Gas and Carburetted Wet Gas underwent various forms of purification to remove tar and other impurities. Coal gas underwent a wet and dry process, with CWG going through dry and Electrostatic Precipitators. This latter stage effectively causes the heavier and very fine particles of tar to be drawn to a bank of charged plates through ionisation. The voltage required for this will have been a hefty 30kV, with the rectification unit being supplied by the Manchester-based Ferranti Company.

Engine House
Coal Gas Exhausters - Arranged between the Condensers and the Wet Purification Plant, consisting of two Holmes-Connersvilles machines driven by an Ainsworth Parker Steam Engine. For redundancy, a Bryan Donkin twin blade rotary exhauster could stand in for either of the Connersvilles. The Donkin being supplied by a vertical steam engine and having a capacity of 200,000 cubic feet per hour.

C.W.G. Exhauster - A single Bryan Donkin three stage turbo exhauster. Originally installed for the Coal Gas system, but later transferred to the C.W.G. stream.

Booster - A single 30 horsepower electric motor with a capacity of 415,000 cubic feet per hour.

Station Meters - Installed for the monitoring of gas production. Two Holmes-Connersville meters for Coal Gas, and a single meter for C.W.G.

Compressors – To provide the numerous high-pressure governors within the supply network, four steam driven compressors delivered gas at 10PSI up to a capacity of 400,000 cubic feet per hour.

Chemical Plant – Used for production and treatment of Ammonia (Concentrated Liquor Plant), Benzol (11,000,000 cubic feet per day), DRI-GAS Calcium Chloride (6,000,000 cubic feet per day), Softened water (5,000 gallons per hour)

Gas holders

Gas holder number 1 - Closest to the northern bank of the River Goyt. 136 feet in diameter, spirally-guided four-lift holder. Volume of 2,000,000 cubic feet. Prior to the gas work extensions, an 1890 site map shows the gas holders as being a two-section telescopic lift with a capacity of 1,000,000 cubic feet, but later works had it changed to four sections, doubling the capacity. A gas pressure as low as 10-30mb was required to lift the sections dependant on extension.

I Holder 1 (Left) and 2 (Right)

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Gas holder number 2 - Adjacent north of holder 1. There is evidence that Gas holder 2 was also replaced or converted during an unknown year due to it being column-guided initially. 136 feet diameter with a volume identical to holder 1.

Holder 2

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Gas holder number 3 – Adjacent west of holder 1. A demolished 1000 ton, M.A.N. Type, 136 feet in diameter with a fixed height of 255 feet. Painted green, known as the green giant and having twenty-two faces. Volume 3,000,000 cubic feet.

Holder 3

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This fixed style of holder would have been a new introduction to the country at the time of installation. The base of the holder was constructed from sections of riveted steel plates laid on a bed of sand and sealed with dehydrated tar. It would be through this base that gas could be pumped in and out of. The shell of the holder acts as a cylinder in which a piston raised and lowered dependant on the volume. It was therefore designed and built so that specially annealed steel plates and channelled stanchions would allow the 800,000 rivets to be driven outwards ensuring the bore of the cylinder was as smooth as possible. It was topped off with a heavily braced steel roof along with a sealing tar storage tank and access ladders for maintenance.

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Access to the upper surface of the piston was done by dropping a collapsible staircase. This would allow inspection on the seal mechanism and the concrete ballast required for working pressure.

The piston seal arrangement deserves time spent on it too, as with most engineering that is unseen, it’s here where great designs remain unappreciated. To contain the gas within the cylinder whilst allowing the piston, which is effectively a horizontal flanged round disc, to slide up and down, the gap between the cylinder and piston edge must be sealed to prevent escape. A gap with too close a mating surface would no doubt cause friction, obstruction and simply wouldn’t work. A tar seal was designed so that the gap could be kept large enough, but designed so that through a flexible barrier, levers, counter-weights and tar, would act as the seal.

Seal system in ideal condition

Seal system compensating for undulating side

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The counterweight is applying a force into the side of the vertical flexible steel plate. Being flexible and hinged allows any undulations to be accommodated. A simple system kept the tar level correct to allow for losses through the mating surface. Tar would flow down the sides of the cylinder, collect in a trough at the base and be collected in a set of five equally spaced tanks. A centrifugal pump would then pump the tar back to the top of the holder. I doubt this would have been an automated process, no doubt it was someone’s job to check the levels at the base and switch the pump on.

C.W.G. relief holder – A spirally guided two lift steel tank with a capacity of 115,640 cubic feet. Located adjacent north of holder 2.

Distribution
Supply pipes to customers were cast iron coated with a black enamel made from coal dust mixed with coal tar. Steam driven gas compressors (booster pumps) were used for the HP supply to Bramhall and surrounding areas.

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Holder 1 & 2 removal works
During the summer of 2019, contractors took to the caps of the two holders like a ring-pull on a tin of beans. We did pay a visit or two during the demolition to get some pictures, but having had a rather one-way confrontational meeting with a ‘security guard’ on another of the contractors site across the river, it just wasn’t worth any further aggravation.

What had been revealed, although just a hole in the ground to most, is a grand bit of work and quite imposing to peer into, with the odd whiff of hydrocarbons. A closer look in the base would have been nice, t’was raining though!

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[Ojay]

Superb, had a few trips here myself before they were demolished this was all that was left when I went last also, sad times

 

[FreshFingers]

Indeed. An eyesore to most (understandable) but some of the final traces of the towns industrial fingerprint smudged out.

 

[urbanchemist]

Interesting stuff - never heard of a lambent retort.
What's 'Benzol' - apparently 11 million cubic feet per day?

 

[Seffy]

Very thorough and detailed report that - just what we like. Like it mate.

 

[Nerth]

An enjoyable read, thanks.

 

[FreshFingers]

Interesting stuff - never heard of a lambent retort.
What's 'Benzol' - apparently 11 million cubic feet per day?

Appears Benzol is another term for Benzene.

 

[mookster]

Very enjoyable read.

There was a similar sized gasworks very close to where I live, although there doesn't appear to be anywhere near the amount of documentation on the internet about it. It was sadly demolished in the late 1960s with the land now a nature park and housing estate, the only thing left being the old dual track gasworks railway bridge that connected the two halves of the site and carried the gas in pipes underneath it from the works to the holders on the other side of the river. I wish I could have seen it!

 

[tigger]

Many things were considered eyesores once upon a time. They start to disappear and you don't really notice it happenning. One day you look around and they've all gone. No doubt an age thing but I miss seeing them as landmarks on journeys. Same with cooling towers and textile mills etc. All huge parts of our social history but people would rather preserve one more useless 'stately home' to add to the huge collection than keep one intact natural draught cooling tower or one gas-holder. Great report but makes me so sad

 

[urbanchemist]

Appears Benzol is another term for Benzene.

Not that it matters, but the number quoted is much too large, whatever benzol refers to (either benzene or a lighter fraction containing a lot of benzene).

 

[FreshFingers]

I agree the figures are quite grand, and sadly in the absence of other documents, it can't be compared against other site references

 

[tigger]

It's referring to the capacity of gas it can wash and not the volume of benzole produced

 

[Alley]

Wow, you've done your research. Very nice

 

[Baggy trousers]

Absolutely loved that, I live in Stockport too and I'm always interested in it's past, this was brilliant. Thanks for taking the time to put this together.