WE HAVE THE GRAPHITE SOLUTION FOR YOUR APPLICATION

APPLICATIONS

  •  Vacuum Fornace insulation
  •  Inert Gas Fornace Insulation
  •  Inert Gas Atmosphere Equipment Insulation
  •  Reaction Vessel Linings
  •  Bearings
  •  Segmented Seals
  •  Piston and Guide Rings
  •  Mechanical Seals
  •  Steam Nozzles
  •  Water Turbine Gland Seals
  •  Packing Rings
  •  Contactless Seals
  •  Vanes
  •  Sealing Strips
  •  Stripping components
  •  Hollow and Container Glass Manufacture
  •  Flat Glass Production
  •  Heat Exchangers
  •  Refractory Systems

INDUSTRIES

  • Aerospace Industry
  • Aluminium Industry
  • Automotive and Mechanical
  • Defense Technology
  • Electronic
  • Glass and Ceramic Industry
  • High-Temperature Applications
  • Mechanical Engineering Industry
  • Metallurgical Industry
  • Non-Ferrous Metal Industry
  • Recreational Products
CARBON AND GRAPHITE PRODUCTS
FOR CHEMICAL RESISTANT LINING
BEARING AND SEALING COMPONENTS
FOR MECHANICAL ENGINEERING

CARBON PRODUCTS FOR APPARATUS AND

REACTION VESSEL LININGS IN THE CHEMICAL INDUSTRY

STANDARD BRICKS

SHAPES

In many chemical processes, apparatus and reaction vessels must be protected against the acidic and caustic materials used in the processes. Apparatus linings made from ceramic or synthetic plastic type materials are often unsuitable, since they may not withstand chemical attack, high temperatures or sudden temperature changes. Alkaline solutions and hydrofluoric acid are of great importance in chemical technology, but they rapidly destroy equipment linings not made of carboncontaining materials.
The carbon and graphite products which have been developed in cooperation with the chemical and acid protection industries, have special characteristics which over many years have proved outstanding in numerous areas of chemical application for the lining of e.g. baths, reaction vessels, boilers etc., and as corrosion resistant floor coverings.
Carbon and graphite linings have a high mechanical strength, good heat resistance and excellent stability to temperature changes. Of special importance is the universal chemical resistance. In the food processing industries, tasteless and odourless carbon materials are valuable. Particularly under difficult chemical and technical conditions in which other materials have been lacking, the special combination of suitable physical and chemical properties of TYGRAF bricks have been extremely successful.
GRADE TYPES OF CARBON LININGS (TYPES OF TYGRAF)
A Standard grade is available which for special applications can be modified by impregnation.
TYGRAF-T: Standard grade
TYGRAF-TX: Pitch impregnated
TYGRAF-TXh: Impregnated with phenol formaldehyde resin
PROPERTIES
TYGRAF characterised by their high cold and hot compressive strength and hardness. TYGRAF brickwork is thus exceptionally resistant to the mechanical demands made e.g. in numerous chemical processes due to the presence of erosive solid materials.
An important characteristic of TYGRAF is its excellent stability to temperature changes which results from the good heat conductivity, high elasticity and very low, reversible thermal expansion behaviour. Thus, for example, high temperature sulphite boilers lined with TYGRAF carbon bricks can be readily sprayed out with cold water without danger of cracking or splitting as occurs with other
ceramic linings.
The density of non-impregnated TYGRAF-T is approximately 1,50 to 1,60 g/cm3. The total weight of a carbon lining is thus significantly lighter than one made of other brick materials, this is often most advantageous with respect to the construction and the statics of industrial plants. When using TYGRAF bricks in apparatus and construction units used for processes involving heat, attention
should be given to the maximum withstandable temperatures given below:
350 °C for non-impregnated bricks in the presence of air/oxygen (T, TX)
>350 °C for non-impregnated bricks in oxygen-free atmospheres (T, tX)
180 °C for material impregnated with phenolformaldehyde resin (TXH).

TECHNICAL DATA FOR CECOLIT GRADES OF CARBON BRICKS

The above values are average values.
Standard dimensions for grades T/TX/TXH:
240 x 114 x 20, 30, 40, 50, 65, 80, 100 mm (stock sizes)
250 x 124 x 20, 30, 40, 50, 65, 80, 100 mm (on request)
Other thicknesses to 100 mm max. on request.
All other dimensions can be made and supplied under contract. These include bends, wedges, small plates, hand moulded bricks, support beams and tubes up to an external diameter of 600 mm.
(UNLESS OTHERWISE SPECIALLY AGREED)

a. Machined pieces e.g. tubes are manufactured in accordance with: DIN 7168 rough.

b. For special dimensions, e.g. hand moulded bricks no tolerances can be quoted and have to be agreed upon.

Besides the TYGRAF-T, TX and  TXH grades, other grades of carbon and graphite in the form of beams or tubes etc., for special chemical construction applications can be supplied. The technical data of these other grades are available on request. On principle, any size and shape can be produced. Moulding methods can be block pressing, extrusion pressing, vibrating and ramming. Hand moulded bricks, both complicated and simple in form are made in the TYGRAF-T, TX and TXH grades. It is recommended to contact us when projects in this field are being planned.

Special sizes and bricks with convex radii can also be made in suitable quantities. To allow us to check the feasibility of manufacture, both quantity requirements and dimensioned drawings should be supplied.

TYGRAF-T carbon bricks are extremely insensitive to all acids, provided they have no strongly oxidising properties. TYGRAF materials also show the same excellent resistance to attack by highest concentrations of alkaline solutions. Alternating acid and alkali conditions are withstood by this carbon material and they are also unaffected by corrosive salt solutions. TYGRAF-T carbon brick linings are thus particularly suitable for chemical processes which involve various temperature and concentration cycles.

The stability of TYGRAF-T, TX and TXH to various chemicals is given in the following table. It is pointed out that there is no difference in stability between TYGRAF-T and TX. Because of its higher density and lower porosity TYGRAF-TX is recommended in surroundings where erosion and oxidation occur. TYGRAF-TXH is impregnated with phenolic resin, and is resistant to oxidising acids up to 170° C. TYGRAF-TXH is unsuitable for strongly alkaline media.
In acid protection and apparatus construction the use of suitable cement is of the utmost importance. This is also important when using our CECOLIT bricks. In many cases the stability of our carbon and graphite material is greater than that of the cement used. Thus, when checking the stability and suitability of the possible carbon or graphite materials, the stability of the cement to be used in the particular application should also be checked so that full advantage can be obtained from the properties of our products.
In the choice of suitable cement, e.g. phenolic or furan resin based, we will gladly give our experience and advise on suppliers of cements, which we do not produce ourselves.

GRAPHITE GRADES

BEARING AND SEALING COMPONENTS
FOR MECHANICAL ENGINEERING

 
Carbon and graphite materials are a proven method for the sealing of shafts and their bearings.
The special physical and mechanical properties of carbon and graphite, in particular their low coefficient of friction, hard wearing and excellent thermal resistance offer solutions to many mechanical engineering and manufacturing problems.
Bearings, sealing rings and vanes made of carbon and graphite may be used for dry or wet running
applications. Their use is recommended where the following conditions prevail:
  • the use of hydro carbon lubricants is prevented by high operating temperatures
  • oil or other lubricating contamination must be restricted
  • chemical attack prohibits the use of other materials
  • minimum servicing requirement
  • dry running and high pressure demands a mechanically sound material with sufficient selflubricating capability, good thermal conductivity and low coefficient of expansion
  • bearings are situated vertically or at an angle in the machine thus making lubricant retention difficult
Bearings and sealing elements Supplied by TYNIC PA materials give the designer many opportunities for solving difficult bearing and sealing problems.

GENERAL APPLICATION INFORMATION

 

PHYSICAL AND MECHANICAL PROPERTIES
  • good dimensional stability (low thermal coefficient of expansion)
  • good heat conductivity
  • good corrosive resistance
  • good temperature resistance
  • good self-lubrication
  • good frictional characteristics
  • good machining characteristics
  • low weight
OPERATING TEMPERATURE
The temperature resistance in an oxidizing atmosphere can be specified as 500°C maximum for TYGRAF bearing qualities. In a non-oxidizing atmosphere the temperature resistance is determined by the final graphitizing treatment of each individual grade (e.g. upper application limit for graphite is approximately 3000°C). Temperature resistance is also affected by various impregnations. In the case of resin impregnation the maximum operating temperature is 180°C, for lead impregnation 200°C and antimony impregnation 500°C.
CHEMICAL RESISTANCE
Carbon and particularly graphite are characterised by excellent chemical resistance to almost all organic and inorganic media. Exceptions to this are some strongly oxidising acids, alkaline solutions, halogens and alkali molten metal.
FRICTIONAL BEHAVIOUR
Graphite has self-lubricating properties because of its crystalline structure. The low friction coefficient is a function of the low bonding between the structural lattice planes. Dislocation of one against the other is therefore easy. The friction coefficient is particularly low if traces of water or other vapours are present. The friction coefficient is greatly increased when a vacuum is created.
Because of the varying conditions of application, no exact data can be given for friction coefficients. In general the following values can be expected for sliding friction:
  • dry friction 0.10… 0.30
  • mixed friction 0.05 …0.10hydraulic friction 0.01 … 0.05
The frictional behaviour of carbon and graphite is also affected by the following factors:
  • running in
  • specific pressure
  • running speed
When running in carbon and graphite bearings, the friction coefficient drops until a constant value is reached once the surfaces are smoothed.
The coefficient of friction also drops in the case of constant specific strain and increasing running speed, or at the inverse.
CONSTRUCTION INFORMATION
The good machining properties of graphite give the designer full scope in producing practical designs.
 
The following guidelines should be observed:
Wall thickness: The choice of wall thickness depends on mechanical aspects. Based on practical operating experience, the graphite bearings should have wall thicknesses which correspond roughly to the empirical equation S = 0.13d + 2.8 ≥ 3 (mm)
Bearing length: To avoid excessive edge pressure and internal stress in the bearing L = d; L ≤ 2d is recommended. The height for washers is recommended as L = 0.1 D • L ≥ 3 (mm).
Flanges: Flange thickness b should be at least as much as wall thickness s (b ≥ s). Flange connections should be radiused and adjoining surfaces machined.
As a general rule: No sharp corners, should be broken or radiused. Shapes should be as simple as possible.
COUNTER FACE MATERIALS
suitable:
  • grey cast iron
  • plain steel
  • alloyed steel (chrome steel)
  • hard metal
  • ceramic
  • glass
suitable under certain conditions:
  • nonferrous heavy metal
  • chrome nickel steel
  • chromium plate materials
unsuitable:
  • aluminium and its alloys
SURFACE QUALITY OF THE COUNTER FACE MATERIALS

The surface quality of the counter face materials has an important influence on the durability of carbon and graphite. Counter face surfaces with a maximum surface roughness of Sr <1 μm are recommended. For high pressure lapped and superfinished counter faces with a maximum surface roughness of Sr<0.5 μm are necessary.

GENERAL GUIDELINES

FOR TREATMENT OF CARBON AND GRAPHITE

Carbon and graphite can be machined to fine tolerances on most machines and machine tools. The work piece remains both structurally and dimensionally stable.
Extraction: Care must be taken that all dust is extracted during machining (e.g. by an industrial vacuum cleaner with a rating of at least 30 mbar and 20 m/s air speed). Lubricated machine driving elements must be covered, moving parts or platens must be kept grease and oil free.
Cooling: The use of cutting lubricants and cooling agents is not recommended. Water may be used as a coolant for honing, lapping and occasionally for cutting and separating.
Clamping: The parts must be carefully and lightly clamped, the clamping pressure should be distributed over as large an area as possible. Parts with a low wall thickness (<0.1 d or <10 mm) must be pre-pared internally with collet chucks or expanding rings. For external treatment it is advisable to place the part on a mandrel.
Tools: The following values generally apply to all turning, drilling and milling tools: clearance angle α: 15° … 25°; wedge angle ß: 65° … 75°; tool orthogonal plane γ: ± 2°, large cutting radii prevent chipping of the work piece. The use of K 05 and K 10 types of hard metal and diamond tools are recommended.

CUTTING RATES

Sawing:
  • High-speed steel and bimetal-cutting band sawblades 3 teeth per inch
  • Cutting speed: 100 m/min
Grinding
  • Silicon carbide wheels, grain 36…60 μm
  • Cutting speed: : 20…30 m/s
  • Diamand cutting wheels, grain 100…200μm,
  • Galvanic and bronze bonding
  • Cutting speed: 30…50 m/s

TYGRAF BEARINGS

 
The use of carbon and graphite bearings has proved successful in the areas of mechanical and process engineering. The use of Graphite Cova bearing materials is recommended for the following conditions:
  • At high and low temperatures, where usual lubricants cannot be used.
  • In media with unfavourable lubricating properties (aqueous solutions, gasoline, liquid gases, water).
  • In corrosive media which prohibit the use of bearings made of other materials.
  • When the finished product must not be contaminated with liquid lubricants (food, drugs).
  • When dry running is preferable to the use of liquid lubricants because of surrounding conditions
  • Bearings with alternating wet/dry running.
  • Concealed machine bearings which cannot be maintained.

GUIDELINES FOR THE INSTALLATION AND DESIGN OF BEARINGS

 
The design of radial bearings and collar bearings of carbon and graphite is determined by DIN 1850, Section 4, „Bushes for slide bearings made of artificial carbon”. Instructions for the location of lubrication grooves are contained in DIN 1850, Section 2 and DIN 1591.
It Is recommended that bores are smooth for dry-running radial and axial bearings. Wet running carbon radial bearings can be provided with longitudinal grooves specific to each case. Grooves are recommended for wet running axial bearings.
 
Normally the bearings are shrunk or pressed directly into the housing or into metal bushings. The low thermal expansion coefficient of carbon and graphite (3 … 5 x 10-6/K) must be taken into account when shrinking or pressing in the bearings.