Brushes in graphite

 

 

 

 

Graphite for electrical use is produced through a mixing process of various powders determined by its final use. Synthetic graphite is the basic compound, common to all categories of graphite. It is produced industrially under a process of purification where all volatile materials (sands, pyrite) in the feedstock are driven off. Successively, synthetic graphite is grinded, sifted and mixed with other compounds such as tar, resins, metallic powders that give to the mixture specific characteristics. The mix are then compacted in small blocks, ready to be process according specific use (size, shunts). Brushes and current collection strips supplied by Cetec are classified as below:

1. ELECTRO-GRAPHITE QUALITY

Electro-graphite is mostly used on CC motors of any electric power . Brushes in electro-graphite can be used from 8 to 12 A/cm2 with temporary maximum limit of 20-25 A/cm2. They fit for peripheral speed ≤ 50m/sec. Electro-graphite has good commutation properties. Electro-graphite brushes have a medium voltage drop and a medium/low friction coefficient.

2. GRAPHITE QUALITY

Graphitic brushes are mostly used on steel rings of asynchronous machines or synchronous with high peripheral speed machines (turbo-alternators) Graphitic brushes are able to cushion efficiently impacts and mechanical vibrations due to the fact that they are soft quality brushes. They bear a current density from 10 to 13 A/cm2 and peripheral speed up to 100m/sec.

3. CARBO-GRAPHITE QUALITY

They are brushes produced with a mix of natural graphite powder and carbon powder. With high hardness benefits, those brushes have good commutation properties also with medium voltage drops and significant temperature resistance. They are mostly used on power tools’motors or motors with low peripheral speed. They bear a current density from 8 to 16 A/cm2 and peripheral speed up to 25m/sec.

4. METAL-GRAPHITE QUALITY

For this category, metallic powders are added in the preparation of the mixture. Production process requests to cook the mixture under controlled atmosphere and adequate temperature to confer solidity and molecule cohesion. Brushes in metal-graphite have a higher conductivity, a low electrical resistance and a low friction coefficient. They are mostly used on electrical machines with continuous current and low voltage, on bronze rings of asynchronous motors, industrial current collectors, asynchronous machines motors with low peripheral speed. In permanent current flow, they bear a current density from 12 to 30 A/cm2 and can sustain current up to 90A/cm2. They can tolerate a peripheral speed up to 35m/sec. This category of metal graphite includes the silver-impregnated quality. This quality has an excellent electrical conductivity and therefore is used on machines and installation that require a minimum current drop. For instance, silver-impregnated graphite are requested for dynamo-tachimetric, in transfer systems (signals and measures).

5. BAKELITE-GRAPHITE QUALITY

The bakelite-graphite quality is obtained by mixing natural or synthetic graphite with synthetic resins. Those types of brushes are obtained by molding. They are brushes with high mechanical and electrical resistance. They can work with low current density. For this reason, they are installed on motors with variable speed, on current convertors, auxiliary exciters. The current density limit is variable, depending on the type of the resin. Generally those qualities have a density between 8 and 13 A/cm2. In any case, the peripheral speed can not exceed the maximum of 40m/sec.

 

Heat exchangers of graphite and metallic plates

 

 

INSTALLATIONS AND COMPONENTS FOR ANTICORROSION

Due to its remarkable qualities, the impregnated synthetic graphite (Carbonite®, trademark Cepic) is the ideal material for heat exchangers manufacturing:

  • Excellent resistance to corrosive fluids
  • Thermal conductivity that is 3 to 10 times greater than metals,
  • Electrical conductivity that is secured to be used in explosive atmosphere environment (ATEX).
  • Low linear dilatation coefficient,
  • Resistance  to temperatures up to 170°C

Thanks to its joint-venture with Cepic, the French anticorrosion equipment specialist, Cetec is able to provide a wide range of products.

Cepic is a Normandy-based company, with more than 50 years of experience in anticorrosion fields.

HEAT EXCHANGERS

Cetec is the ideal customer support to shape and build adapted solutions and if necessary personalized products for heating, cooling and condensing  corrosive fluids.

  • Cylindrical vertical graphite heat exchangers
  • Cylindrical horizontal graphite heat
  • Cubic section graphite heat exchangers
  • Horizontal channel heat exchangers

Anticorrosion solutions are sized in function of customer’s process and application specifications.

They are all manufactured in conformity with the European Directive PED 97/23/EC.

MAINTENANCE SERVICES

Cetec provides to its customers maintenance and repair service activities for heat exchangers in graphite or with metallic plates, pumps, agitators and filters in graphite including the complete repair or substitution with original spare-parts of dysfunctional elements.

 

Graphite for high temperature

 

 

Graphite is made of crystals organized in parallel strips of Carbon atoms, aligned  as hexagonal atomic structure.

Graphite is used in countless areas, because of its electrical inertia, its mechanical properties in high temperature context and for its thermal and electrical characteristics.
From electrical applications (brushes for motors, current collection strips) to steel industry (products for metal continuous casting). In chemical industry (heat exchangers, pumps, rupture disks) and in aerospace (nozzle for rockets).

For some of those applications, graphite is employed through an isostatic compaction process. With this process, we can obtain semifinished graphite with  very small particle size (high density) and with chemical and physical characteristics, similar in any direction.

With a wide range of isostatic qualities, and strict and controlled production process, Cetec can supply products and components such as:

  • Monoblock ring or with radial section segments for mechanical sealing
  • Bearings for pumps, valves and vanes
  • graphite die and iso-molded graphite for continuous casting
  • electrical resistance;
  • dynamic sealing;
  • carbon vanes for vacuum pumps and compressors

Cetec also offers different qualities of graphite to manufacture electrodes for electroerosion (EDM).
Cetec low-porosity graphite allows to perform precision tasks with  a low geometrical deformation during the erosion operations and a good metal removal with low roughness.

The graphite qualities available cover all kind of working contexts and requests. Graphite with a high removal capacity  and a high finishing quality level. Graphite for a high quality precision works  and high finishing quality level
 
To complete the portfolio, CETEC also supplies extruded graphite.

This graphite shaped by extrusion is required mainly in the steel industry with electrodes  or in production cycle of non-iron metals, in particular aluminum. The main characteristics are:

  • Good thermal conductivity;
  • Excellent resistance to thermal shock;
  • Easy to  operate;
  • Good expansion coefficients;

With those extrusion graphite, Cetec produces:

  • Calibration rings for aluminium extrusion;
  • Sliding runners for aluminium plates;
  • Agitators;
  • Components for metallurgical ovens.

 

Anticorrosion pumps

 

 

CORROSION RESISTANT PUMPS

Centrifugal pumps ensure the safe transfer of corrosive liquids. Depending on the model, they can handle flows from 1m3/h to up to 700m3/h and discharge heads of from 2 meters to up to 130 meters. Each pump is adapted to customers’needs. Cetec can suggest upon request solutions adapted to specific applications:

  • Horizontal standardized pumps
  • Close coupled pumps
  • Magnetic driven pumps
  • Submerged vertical pumps
  • Vertical pumps

 

Rupture Discs

 

Rupture Discs

 

Rupture disc is a key pressure device that protects the pressure equipment from over pressurization or potentially damaging vacuum conditions. It’s a one-time-use membrane, in fine-grain synthetic graphite.

Cetec can supply rupture discs in conformity with PED 97/23/CE.

  • Monobloc medium pressure discs
  • Monobloc medium pressure discs for operation in vacuum
  • Monobloc medium pressure fluorinated polymer film
  • Monobloc high pressure discs
  • Low pressure removable membrane discs
  • Medium pressure removable membrane discs
  • Special discs

Brush holders

 

 


The large range of models of Cetec brush-holders is produced by fusion of brass alloy of premium quality.

The use of brass guarantees a high heat dissipation  that reduces advantageously thermic stress undergone by graphite brushes.

Each piece is carefully controlled in order to reduce non-quality and guarantee the best production of  brush-holders.

The product range includes:

  • Single brush-holders
  • T brush bolts
  • Plug set brush-holders
  • Thermosetting and thermoplastic brush-rockers
  • Insulated brush bolts for clamps
  • Tubular brush-holders
  • Pressure system (wound or coil springs)
  • Various accessories and spare parts.

Upon request, Cetec can realize surface treatment  on brush-holders and other components to prevent corrosion.

 

Slip Rings

 

 

This Cetec business area is divided in two main segments:

  • Production of slip rings upon existing model or customer design or new design.
  • Maintenance of existing slip rings

Cetec can provide a wide range of slip rings, such as:

  • Standard slip rings collettori stampati from 3 to 8 rings.
  • Slip rings stampati ad anelli frontali;
  • Slip rings ad anelli assembled in bronze or steel of any diameter ;
  • Slip rings assemblati ad anelli multipli;
  • Prese di corrente rotanti ad anelli in bronze, silver-covered bronze, or silver;
  • Slip rings realized upon specific request from the customer, tailor-made.

Cetec Maintenance Service is able to rebuild entirely or partially whatever kind of slip rings.

Upon request, balancing services can be provided.

 

Fusions in brass and bronze

 

 

Cetec is the perfect interlocutor to satisfy all kind of customer request for fusion in mould shell or in sand in cupper alloy (bronze, brass).

The pieces can be supplied in different versions: raw casted or finished as customer design’s request with mechanical finishing operations. During the degating operations, a unitary visual control is done to check the quality of the pieces.

If requested, the following controls and certification can be provided:

  • Chemical analysis of the material;
  • Physical tests (Traction, compression, flexion)
  • Dye penetrant inspection;
  • Radiographic testing.