I just assumed a mould was simply made when a customer approached a manufacturer and the moulds stuck on a shelf until needed again – appears I was very wrong. John Bramall gives some fascinating insight into brick mould manufacture and ownership.
Moulds
Mould charges in the Refractory industry.
Experience at GR-Stein Refractories Ltd. 1969 and 1975-1983.
At that time GR-S had a number of plants – in Scotland there was Glenboig (firebrick),
Dykehead (firebrick) Castlecary (firebrick and fireclay monolithics) and the largest works
Manuel, Linlithgow (firebrick, high alumina and basic bricks).
There were several plants in England – Worksop (Basic bricks and monolithics),
Hipperholme, Halifax (insulation bricks), Bawtry (Carbon, high alumina), Meltham and
Deepcar (both silica and silica-based monolithics), Deepcar Monolithics (alumina-based
monolithics) and Ambergate (Insulation monolithics). Hirwaun in South Wales was a closed
plant) had made silica and then basic bricks) used as a storage/stocking location for
customers in that area.
I don’t know how the mould charging was done at different manufacturers but this was my
understanding of the way it worked for some of the big projects when I was at GR-Stein
between 1975 and 1983. Someone had to pay for the moulds for ‘special’; shapes i.e. those
specific to that project or that client. I recall that coke oven projects had 1000s of silica
special shapes and they all needed moulds that had to be paid for.
Of course, usually the brickmaker would absorb some of the cost – hence ‘part mould costs’
in order to a) win the initial order and b) to help ensure they get the repeat business and c) to
allow them to use those moulds for other customers’ orders. And of course, sometimes they
wouldn’t charge mould storage charges to help them win the business. It was sometimes a bit
of a negotiating tactic. For example, if 2 competitors were quoting similar prices for a
project, they might improve the terms of trade for the moulds (cut prices or free mould
storage) in order to give a discount without cutting the brick prices.
Major projects came up at regular intervals but with big gaps. Blast Furnaces – 5 to 7 years,
hot blast stoves – 15 to 20 years (timed to coincide with their BF relines). Coke ovens – 20 to
25 years. Glass tanks -10 to 15 years. Cement kilns 2 to 3 years with interim partial relines.
Furnaces and ladles had campaigns of various lengths.
In the bulk-steel making business – ladles and BOFs / BOVs (Basic Oxygen Furnaces / Basic
Oxygen Vessels) – it is all about campaign lengths – campaign lives are routinely extended by
adding layer upon layer of refractory monolithic material spun onto the top of the original
brick lining. The monolithic layer would be the sacrificial wear component – lives got up to
2000 + and became the standard.
Standard shapes, usually laid down by national and international standards were used by
many customers – there were no mould charges for those shapes.
And of course, some customers (e.g. Karrena, Liptak Bradley, MH Detrick) had their own designs and kept
sets of moulds at different suppliers including foreign suppliers so that could –
a) get competitive prices
b) help ensure continuity of supply
c) they could develop their own technology by using their branded or even patented shapes
specific to their needs.
It was all about negotiating the commercial ‘package’ –
Say a project had 500 moulds required (which was not unusual) and the cost was going to be
an average of £200 per mould to make them in-house then the total project cost would be –
c.£100,000. So the brickmaker could charge the client, say, £100,000 full cost no profit, or
maybe say £120,000 including some added profit and in either case the moulds became the
client’s property and they might then charge the client an annual mould storage charge, and
then a refurbishment charge when and if they were used again for an identical or similar
project for that client.
The client could take the moulds away if they wanted though they would probably have to be
modified or refurbished when / if used by an alternative supplier. But what the brickmaker
usually did was to charge, say, £80,000 or £90,000 and call it a part-mould charge
and retain ownership. That meant the moulds could also be used by the brickmaker on other
projects. The original client would not incur any mould storage charges but would have to
pay a refurbishment charge if necessary.
There was generally no mould charge for standard shape bricks which were sold to many
clients and were often ‘stock’; bricks available from stock or on short order, of say, 2 to 10
weeks depending upon the type of brick and the lead times. Specials were usually on 10 to 25
week or longer lead times. Big lining orders for hot blast stoves would be planned and
ordered a year ahead with the design, estimation and quotation being done a year or more
before that. Sometimes GR-S would have 3 or more blast furnace/hot blast stove projects
going through at once and the management of these projects was quite complex!
Sometimes would order a complete lining to be held in stock ready for shipment when the
time came for a relining to be done. The cost of such a lining could be £250,000 to £500,000
or more. If such an order was held in the supplier’s works then the pallets were marked up as
being the property of the customer, not the supplier to comply with insurance requirements.
Experience at Dyson Refractories Ltd. (J & J Dyson Group) 1965-1968 and 1972-1973
Casting (Pouring, USA term) pit holloware manufacturing works, Stannington, Sheffield.
Casting pit (pouring pit) holloware refractories (such as runners, guides, trumpets and
centres) and ladle control refractories (such as stoppers and nozzles) at that time were made
from very plastic, very mouldable clay mixes and the industry was dominated by the
Sheffield area manufacturers. They based their mixes on the Stannington pot clay seam that
underlies some of the hills between the Rivelin and Loxley valleys to the west of Sheffield
around Stannington, Dungworth and Ughill.
The three main UK manufacturers were Dysons at Stannington, Sheffield and Thos Wragg &
Sons Ltd. and Thos Marshall & Sons Ltd (Marshall Group) both based in the nearby Loxley
Valley. The three works were similar in size at c. 30,000 tonnes per year each – all operated
in a similar way with similar manufacturing equipment. There were other, smaller, casting pit
holloware brick makers in the UK – a Dyson Group company (John Knowles) had a works at
Swadlincote as did a Wragg’s sister company, Marshalls had a small works near Wrexham.
BSC Refractories Ltd. had casting pit refractory holloware brickworks at Lowca near
Workington in Cumbria and at Newfield near Crook in the North East.
At Dyson’s Griff Works Stannington (casting pit refractories manufacturing plant) they made
a lot of their own design presses – I think they were more advanced in some ways than local
competitors, Wraggs and Marshalls. Drop stamps (I think) and maybe some moulds came
from a local company called AMCO (Albert Marsh & Co) or from Leonard Hall (Patterns) in
Sheffield or from a Marshall sister company MIA (Modern Industrial Appliances) in
Sheffield.
Wraggs West Plant – the last (and most modern) plant to be opened in the area was opened –
c. 1970 – it had an optimum layout and had a lot of automated presses from Germany for
making the smaller cross-section items such as runners and guide tubes.
Mould maintenance was done in-house – Dysons had a good facility – with maybe 10
machine tools – drills and lathes etc. Wraggs and Marshalls had similar facilities.
Dysons and Wraggs had their own joinery shop making wooden moulds. I expect the same
happened at Marshall’s. Dysons made a lot of fireclay hand-made ‘coal savers’ and press-
made firebacks for the retail trade. Rayburn was a brand I recall.
Dyson’s joinery shop made the wooden moulds for the hand moulders. They were sometimes
metal lined or more often metal-edged to protect the wood.
It was the steel moulds that were bought in from Leonard Hall Patterns and AMCO. The
steel moulds came as a ‘carcass’; with an inner steel lining and top which wore away during
the brickmaking process. It took about 2 days for the abrasive clay mix to wear them down
such that the bricks were becoming out of size – too big or the edges became less square than
required. The moulds were then taken off the machines and taken to the fitter’s shop where
they were repaired/relined. A replacement mould would be put back on the brick-making
machine – the replacement mould might be for the same product or for a different product
depending upon the orders on the production schedule for that week for that machine.
The moulds were lubricated with a type of paraffin-based oil which was splashed into the
mould between each stamping to stop the clay mix sticking to the mould sides and the stamp
or press plunger walls. The liquid was transferred from a tin-can holder using a ‘dolly-brush’
– the operatives got liberally sprayed with the oil which could cause skin allergies!
Hand moulders used the same lubricant. The lubricant tin cans were refilled – supplies being
drawn from 50-gallon (200 litre) drums as necessary.
Dysons bought in thousands of wooden pallets and crates from Norman Charlesworth’s
joinery works (and funeral directors) in Stannington village. Charlesworths also supplied
pallets and crates to Wraggs and Marshalls. Lorries returning to the works picked up loads on
their way back.
Mould manufacture – contraction/expansion during the drying & firing process
Refractory bricks will generally contract or expand during the drying and firing cycle as the
water or binders within the ‘green’ product are removed by the heating process. The changes
in the chemistry of the products during the drying-firing cycle also makes physical changes
which often include changes in dimensions as the brick shrinks or expands.
The amount of contraction or expansion depends upon the nature of the material; the blend of
the batch or mix and the method of manufacture. A dry pressed brick will have little change
in finished dimensions whereas a product manufactured from a water-based wet mix will
shrink a lot. Some products such as silica expand during the firing process.
The nature of the batch mix includes the choice of material; the sizes of the particles and the
type of binder used. The binder could be water or sulphite lye or phosphate or tar or one of
the other binders in use in the industry. What is important is that the batch mix must be
consistent in line with the recipe to make a particular specification for the finished brick.
Moulds have to take account of the expected dimensional changes so that the finished size is
correct.
At Dyson’s, Stannington, Griffs Works, casting pit (pouring pit) and ladle flow control
refractories were manufactured by a wet plastic process with the wet batch being made into
hand-made shapes or following de-airing being drop-stamped or pressed into shapes. The
batch used a mixture of clays which themselves had their own contraction rates and it was
key that the blend and particle sizes used in the batch prepared for brick manufacture were
selected to give a finished product with a known and consistent contraction rate.
At Stannington, it was one inch to one foot (12 inches) contraction during drying and firing.
The binder water from the clay mix evaporated at c. 200C and the water of combination of
the fireclay at c. 700C. The drying and firing cycles were planned to allow slow release of
steam so that the bricks wouldn’t explode during the heating process.
I remember that all the metal rulers in the making sheds were made especially to read ‘as
finished’ sizes. So, a ruler would read, say, 12 inches but it would actually be 13 inches. A
maker could measure a newly drop-stamped or hand-made 12-inch brick (13 inches long
actual length) but the ruler would read 12 inches. And pro-rata.
At Griffs Works the run-of-the-mill batch comprised a blend of Stannington pot clay
(contraction 1 inch to 12 inches); a Swadlincote clay (2 inches to 12 inches); a Scottish clay
(0.5 inches to 12 inches) and grog – recycled crushed fired bricks (nil contraction). The
alumina content (as Al2O3) was different for each constituent but the blend when fired was
planned to be c.36% with consequencent and appropriate physical properties and
refractoriness.
I guess silica bricks would expand during firing so that would have to be factored in as the
moulds would have to be ‘under size’ to allow for that expansion. The firing of silica bricks
required a very complex schedule to avoid damaging the bricks.
Richard John Bramall – 16th December 2023.
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Harry Baird, an employee at the Stein Manuel Works Whitecross points out that all internal mould corners were rounded otherwise the corners would crack across the angle.
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Harley Marshall, ex export manager at the Stein Manuel Works, Whitecross says that the moulds were very often made from yellow pine and lined with brass to stop the clay sticking.
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