Description of Plant, Processes, etc.

1. Producer Gas Plant

Although a coke oven gas supply pipe was put across this area during the war, the Works is still awaiting its connection. It has its own gas producers numbering 18; 10 are automatic insofar as

they have revolving grates and 8 are simple static ones. One of the former was working at the time of the visit, supplying washed gas to the neighbouring Works; normally a greater quantity is supplied. Brown coal (water content 55%) is used; this is brought up from the firm's own wharf on the Rhine in wagons and transferred to overhead bunkers by travelling crane and grab.

A total of 450 tons of coal used to be gasified per day, giving 25,000 metres washed gas per hour, this measurement being made by a venturi tube. The tar was removed by first cooling to 80°C. and then by passing through a centrifugal machine into which hot tar was sprayed, the temperature rising to 85°C., this preventing water condensation at this stage. The de-tarred gas was then washed with water, the temperature falling to 20°C. The approximate percentage composition was said to be 2-4 C0₂, 18 CO, 12 CH₄, 50 H₂ and 18 N₂. The gas was described as cheap but poor, having a calorific value of 1,300 cal. per cubic metre. Tar was reintroduced at the furnaces (see later.) They had no burn-outs.

2. Mixing Room

This is located in the basement of the Furnace Hall. It was described as out-of-date and containing much rubble from bomb damage and was not closely inspected. The batch was brought up into the Furnace Hall by hoist from an Eirich mixer and dropped into large hoppers which could be moved over the filling machines when the latter were brought up to this end of the hall or could be run on to side rails until required. The rails for these hoppers are about 8 ft above the floor and there are about 12 hoppers in all, each holding at least 4 tons.

3. Furnace Hall

The four 16-pot furnaces are in line with the batch-handling plant at one end and the Bicheroux machine at the other. Along each side runs a filling machine and a pot-handling machine, there being no overhead cranes. The furnaces have a single port at each end. The tar was reintroduced into the gas in the gas up-take through oil-burner fitted with a fine orifice, the tar supply lines being steam-heated. Compressed air was used for atomising and the burners were protected with water-cooled jackets.

Founding Cycle The glass made here was for normal polished plate and was decidedly green. Its percentage composition was given approximately as 72 SiO₂, 12 CaO, 13 Na₂O, etc. with 0.5 Fe₂O₃. No special glasses, including white glass, were made here during the war. All the cullet made in the plant was used up. The founding cycle took 27 hrs., casting being 3 hrs. later each day, giving 6 casts per week. A 24 hour cycle was said to be out of the question because the fuel was not good enough.

Details of the cycle were given as follows; the temperatures being approximate and said to be determined by optical pyrometer sighted on the siege.

Records and charts for the furnaces were said to have been destroyed. Several pots were in or about the furnaces. These contained the greenish glass and showed heavy flux line attack but few or no “fangs.” The pot wall thickness was 4œ" to 5" and the capacity 1,100 litres.

4. Casting Hall

The pots are put down on a travelling car and picked up by the teaming crane of the Bicheroux plant. A bomb had fallen between the guillotines, damaging the rolling plant and tables. There are 2 tables and 2 lehrs of the kiln and moving rail type. The kilns have 5 positions and the rails 22 making 27 in all. The tables are not heated; no sand is used but graphite is thrown on. Thin glasses go through the lehr in 1œ hrs. When thick glass has to be made only one or two plates are cast and these are at the end of the days cast, so that they can get 13 - 17 hrs. on the lehr rails. The normal thickness made was 9 mm. rough cast to give 6 mm. finished. The thinnest finished glass was said to be 2 mm. and the thickest 25 mm. The kiln beds are 14 years old and in fit condition for restarting. The station temperature was given as 430°C; there was said to be automatic temperature control in the kilns. (Note. This may however mean merely automatic temperature recording.)

5. Pot Rooms

Some work was going on here making regenerator bricks, etc. French clays (Provins: Etienne Henri, Delondres, St. Loup) and Belgian (Ardennes: Reunis, Thimsonet) are used in preference

to Grossalmerode (which was described as too expensive as well as unsuitable for plate pots) although the latter is used in making blocks etc. Ground silica is obtained from Grosspeter Lindemann A.G., Cologne. All French clay is used in the pot mixture if available. About 60 pots are made per batch, succeeding batches seldom being alike since some Belgian clay is added according to the state of stocks and deliveries. A batch (described as typical) in the records is as follows:-

The synthetic grog is burnt up to l,200°C. but the preference is for soft rather than hard-burned grog.

The pots are made on stillages and are then transferred to a dryer where they remain 16 - 20 days. This dryer consists of one large chamber but has a single track without any cars. The various shapes inside were on stages. The pots are subsequently stored for a period up to 6 months in hot rooms. The sound pots in stock number 300 - 400. There is only 1 pot maker available at present; 1 pot maker with 1 assistant will make 1 pot in one 8-hour day.

The pot arches take 2 pots each. There are 7 in all, 3 being electrically heated and 4 gas heated. The arching temperature was said to be 1,100°C. and the arching period only 3 days. A further arch is used for firing blocks; this has recuperators.

6. Grinding and Polishing

This department has been damaged by several bombs. There are 18 tables, 5 grinders and 6 polishers. The tables are 6 m. 40 cm. diameter. Both sides are laid on cloth. The grinding time is 35 minutes for 1 side and polishing 60 minutes. The sand is used in 11 grades. There are also 2 other polishers for similar tables said not to have been used for many years. The washing machine takes the glass almost vertically and has a brush compartment only 4 ft. long. An acid wash is used. This was given up for a time but its use was later recontinued.

7. Warehouse

Although the building is badly damaged, with parts of the walls completely down, all windows broken and part of the roof off, a few cutters were working on circles for silvering. In the main shop plates are examined vertically against white cloth screens placed before large windows. The cutting tables here are of the tilting type and there is an overhead crane. The other shops are badly damaged and contain no glass. The glass seen contained seed.

8. Cullet Tank

The furnace hall contains a small cullet making tank operated to provide cullet for a neighbouring Works. The ribbon produced would be about 50" wide in 3 mm. substance and would move about 40 ft. over open rollers before being crizzled by a trickle of water so that the fragments fell into a steel hopper with a gate opening above a wagon in the basement.

Description of Plant, Processes, etc.

Two pot furnaces are ready to start up, there being a stock of 330 pots. It has been the practice here to keep a third furnace as a stand-by.

Belgian and French clays were used for pot making.

The grinding and polishing plant has 5 disc grinders and 5 disc polishers, the tables being 9 metres 20 cm. diameter.

Prior to its shut down, 3 years ago, this Works made only polished Plate glass and no coloured or special glasses; also it made no war products.

NOTE The above data was obtained by interrogation of the Manager, but the plant was not inspected.

Description of Plant, Processes, etc.

This Works was related to that at Waldsassen. Plate glass was made here before the war, being ground and polished on the premises but this plant has now not been used for several years and there appears to be no likelihood of polished plate glass being made again. On the other hand, this Works can apparently meet competition with its wired glass cast intermittently. There are no stocks of glass but there is a three weeks' stock of raw materials.

The factory contains two very small tanks, practically square. They are cross-fired from two stacks. Filling is done by hand. Gas is supplied from two “Demag” producers, one to each tank.

There are two rolling machines for the manufacture of wired glass, and a plate of 6 - 8 mm. thick glass 4 metres long by 1.08 m. wide (157œ in. x 42 in.), was cast on each machine (when both tanks were in operation) every 5 or 6 mins.

Three types of wired glass were made:

6 mm. mesh (unwelded) Georgian
12 mm. mesh (spot welded) Georgian
Hexagonal

Very small quantities of the latter two types were manufactured. The wire was bought from Niederlahnstein.

Composition of Batch:-

Description of Plant, Processes, etc.

This Works is claimed to be the only one producing coloured glasses by a flat-drawn process. It is said to have no stocks of glass left.

The factory is equipped with one small tank and one Fourcault machine 1.2 metres (47 inches) wide.

The chief product has been Coloured Signal glass drawn as follows:-

• 2 mm. thick - 1,000 sq. metres per day 23"/min.)
• 3 mm. thick - 850 sq. metres per day 19"/min.)
• 5 mm. thick - 400sq. metres per day 9œ"/min.)

Ordinary Sheet Glass has also been produced from time to time in this factory.

Comments

This organisation is a city office handling the sales for the Gerresheim and Bergisch-Gladbach factories of the A.G. der Gerresheimer Glashuttenwerke vorm. F. Heye concern. These factories are described in Report XX and Report XXIII respectively

General Interests of the Gerresheimer Organisation

The organisation is large and has wide interests. In addition to producing numerous types of containers, rolled glass, glass bricks and glass wool it also produces plastics, chiefly

bottle caps. It is interested in the following companies:

At Minden the production of very large carboys by an automatic blowing method was undertaken and since production is expected to restart towards October 1945, this factory should be noted for special examination.

Description of Plant, Processes, etc.

1. General

The plant is divided into four sections, making

respectively bottles and wide mouth containers, glass wool and silk, flat glass, and glass bricks. The plant is large, possesses 10 tank furnaces and is capable of producing amongst other products a million containers per week. Owing to shortage of fuel, damage and the removal of the more delicate parts of machines to avoid damage, only one furnace was in operation and that had just commenced making a rolled sheet (Clear Rolled) glass. Essential parts of machines for making glass wool and all the plant for asking glass silk had been sent to Ettlingen near Karlsruhe and Dresden at the beginning of 1944. Some of the container making machinery had been dispersed to Rinteln, (Map ref. L53/B99)

2. Gas Supply

In normal times there were two alternatives: (a) Gas by direct pipeline from the coke ovens and (b) Producer gas. The former was not used if it could be avoided because it cost 4 Pf. per cu. m. as compared with producer gas at 2 Pf. per cu. m. (1 pf. = 0.06d.)
[Glass Study.com: 1 pfennig = .06pence is same as 40 Marks=£1]

There were five mechanical type producers made by DEMAG. They were fitted with automatic filling devices from overhead bunkers and had automatic agitators and automatic ashing device. Lignite was the fuel used.

One producer normally supplied gas for one tank furnace. The present fuel was poor and it had become necessary to operate three producers to provide a gas supply for one tank. Each producer gasified 40 tons of lignite per day under normal conditions. For blast, air was passed through water and then through a superheater (which received its heat from the hot producer gases) and entered the producer at a temperature of 150°C. The gas passed through a dust chamber to enter the flue.

3. Mixing Room

This was very old, consequently the methods used were antiquated. It appeared that plans had been drawn up prior to the outbreak of war for a completely new mixing room but its construction had to be abandoned. All the raw materials were available fairly locally and reasonable stocks were available on the premises, namely:- Sand (obtained near Cologne) 2,000 tons; Soda ash 500 tons and Limestone 500 tons. The following quantities of raw materials were necessary for one month's supply for normal rolled glass:- Sand 1,000 tons; Soda ash 450 tons; Limestone 100 tons; and for the normal production of the whole factory:-Sand 5,000 tons; Soda ash 1,200 tons; Limestone 1,000 tons. It was said that 10,000 tons of fuel per month were necessary for this load.

There was only one weighing machine which gave direct weights and cullet was mixed with the raw materials in an Eirich mixer.

For the first 40 Kg. (88 lb.) of Saltcake there was no addition of anthracite to the Batch. Should, however, the saltcake content be increased a small amount of anthracite was added. The mixture of batch and cullet was fed to the tank from a fixed overhead hopper.

Glass compositions are given in Table IV.

4. Container Section

There was nothing novel about the bottle making plant. The glass was melted in tank furnaces (lined with Didier or Dr. Karl Otto's clay blocks) and fed by Hartford feeders to the bottle making machines. The tanks melted 1.2 tons of colourless glass or 0.7 tons of hard green glass per sq. metre of melting surface per day, and were fired with producer gas. The life of the furnaces was 12 months. The installation was a large one producing in normal times a million containers per week. The Steigenwald and Uthardt lehrs were said to be very satisfactory.

5. Glass Brick Section

The Company were also licensees of the Owens Coming process for making glass bricks (approximate size 9 x 5 x 4œ in.) for building purposes and before the war could make 10,000 half brick sections per day. They possessed one heavy duty press for this work but also had under construction an automatic press of their own design.

The half sections of the bricks were joined together by aluminium but as they had not been permitted to use metal for this kind of work since 1943 they had experimented with fusion processes for sealing. Glass bricks, however, had not been produced during the past two years.

6. Rolled Sheet Section

Load 70 tons of glass per day

Refractories All tank side, bottom and bridge wall blocks were of Chamotte by Didier Werke. Corhart blocks were used in the throat of the doghole. The tank had three courses of side blocks without tucks tones.

Stacks Three each side, all worked full open. Half-hour reverse with Dyblie type valve for gas and butterfly valve for air.

Crown Customary type Silica (Dinas) bricks. Flow end portion insulated.

Bricks by Didier Werke. Checkerwork passages straight with very wide spacing.

Repairs Every 12 - 13 months

Temperatures Melting end 1,400°C. Flow end 1,250°C. as indicated by crown thermocouples. The tank was square ended with one canal in each side of the flowing-end wall. The tank appeared to be left very much to its own devices, very little attention being paid to control. There was not even one open sight hole into the tank, either at the filling end or flowing end.

Casting Machines Boudin type; two kinds of rollers were used, namely ordinary cast iron and special heat resisting steel, both supplied by Krupps. Roller dimensions were:

Tray rollers led from machine to lehr with very slight fall.

Lehrs Gear driven, hand oiling. Length 90 metres. Direct heat top and bottom. The first twelve rollers were asbestos discs on iron core and the first forty rollers were water cooled by means of hairpin pipes. Before the war only one lehr was operated from this tank, but hand ladling was also in use. A second lehr is now nearly completed and will be in operation at an early date. The present ribbon width is 1.3 metres (51") but that from the second lehr will be 1.6 metres (63"). The substance tolerance is 0.1 mm.

Speed of Flow This was given as follows:-

3-4 mm. substance - 2.4 m. per min. (94.5"/min.)
6-7 mm. substance - 1.3 m. per min.

The glass was packed direct at the lehr end by two carriers.

Production was at the rate of 4,000 sq. metres (43,000 sq. ft.) per 24 hours at the time of the visit.

Cutting Normal edge and centre split. The cross cut was done by hand, there being two cutters who also stripped the edges, one at either side of the lehr. The length cut was hand measured on each sheet by lath.

Quality This was exceedingly poor even for Clear Rolled glass.

Rates of Pay Average rate for Teazers and Machine Operators was 80 pfennig per hour for a 40 hour week. A bonus of 40 marks per month was payable.

7. Glass Fibre Section

(a) Glass Wool

This factory has two glass melting furnaces which have been used to make thermal insulating wool. One of these furnaces has two fore-hearths with four blower-equipped fibre-forming bushings attached thereto while the other furnace has only one fore-hearth with four bushings. One of these fore-hearth3 may be equipped with six bushings. It was stated that each four-bushing fore-hearth produces 10 tons of wool per day. No production has been scheduled since 3rd March, 1945, when the Allied Armies passed through Gerresheim. During the early part of the war, ordinary lime-soda-silica wool was made. The last wool turned out however, was made by melting oil shale from which the oil had been removed. The raw material melted was therefore a waste product of shale oil distillation. The wool produced was of a light brown colour and filled with many but very small black “slugs” of non-fiberized material having the appearance of a high grade rock wool. This product should be a very satisfactory thermal insulation for general use and was stated to have a safe working temperature range up to 800°C. (1,472°F.) It was packaged by simply rolling it up with a light weight paper separator at a width of about 15 inches or more and placing rolls about 12 inches in diameter in cartons. The stock was in rolls simply held with paper tape. The thickness of the pack of fibre constituting the rolls was about one inch and the density is estimated to be about three pounds per cubic foot. The fibres were lubricated with emulsified mineral oil but due to lack of proper materials, cheap grades of stearin pitch were reported to have been used as a substitute.

The fibre was formed by passing the molten glass down through holes in platinum bushings which were heated by electrical resistance to control the viscosity of the flowing glass. The actual drawing of the fibre is accomplished by steam blowers directed downward on opposite sides of the flow holes and several inches below the orifices. The downward flow of steam reduces the pressure of the atmosphere by the accelerating atmospheric movement. The fibres thus formed are about 0.00035 inches in diameter and these, together with the non-fiberised glass drop through a metal enclosure into which the lubricating oil is sprayed. The material collects on a wire belt conveyor having suction underneath and the product passes out over a moving sheet of paper, to be cut to various lengths and rolled up.

The composition of this wool is as shown in Table IV.

(b) Glass Textile Yarns

The textile department of this factory was damaged by fire in November 1943. Owing to the essential nature of this material for electrical insulation of war equipment all of the machinery was moved to Ettlingen near Karlsruhe. The plant was to be rebuilt in Pfortzheimer Strasse at Ettlingen and Dr. Claus Siegfried was sent to that address as plant manager. It is now understood that Dr. Siegfried is returning to Gerresheim but apparently the plant has been operated at the new address. (See Report XXI on Ettlingen Factory.) Both Staple and Continuous fibres were made at the original plant in Gerresheim.

Staple Fibre appears to have been made in considerable quantity. Samples of sliver were shown which were reported to consist of fibres having a diameter of about five microns. This product was wound on paper tubes and had a meterage of 16,000 per kilogram. This sliver, it was stated, has been used in the twisting of yarns for the weaving of fabrics used by the Robert Bosch Company of Stuttgart in making impregnated sheets for use as a substitute for mica. (This is the same as “glashartgewebe,” a product made at Peuerbach as reported by Mr. Fred E. Henderson of T.I.I.C. Communications Division.) This fibre was reported to have been made by blowing molten glass from a platinum bushing on to an evacuated perforated, revolving drum from which the fibres are pulled on to a revolving spindle. The sliver so made is then twisted and plied into yarns. Dr. de Ruyter was stated to be the inventor of the resin bond for twisted staple fibre.

It was stated that the Schuller Glass Wool Company of Coburg makes a staple textile product. (This plant was visited later; see Report XXVI.)

Continuous Fibres are made by drawing glass fibres from a bushing by means of a high speed winding drum. This Company has done some yam twisting and winding but has never done any weaving. All of the actual cloth, tape or braiding fabrication has been done by regular textile concerns. This product has been used largely for electrical purposes.

The compositions of these yams are given in Table IV.

TABLE IV

GERRESHEIMER GLASS COMPOSITIONS