GRAPHITE MOULDED DIE
FORMED RINGS
Flexible graphite die-formed rings are valve stem packing rings manufactured from high purity flexible graphite foil with a corrosion inhibitor but without any binders, elastomers or fillers. Graphite Moulded Sealing Rings are produced using a pre-determined length of flexible graphite tape which is then, using a mould, compressed to form a solid ring of precise density and size. For ease of installation, when the valve bonnet cannot be removed, split rings should be used.
We have four model numbers of graphite moulded rings, Style 1, 3, 4 and 5
Model 1, 3 and 4 are manufactured in exactly the same way and have the same main characteristics, only the purity of the graphite used changes.
Model 1 – 98% is commercial grade and makes up the vast majority of usage for industrial applications.
Model 3 – 99% conforms to Shell material specification MESC SPE 85/203
Model 4 – 99.85% is exclusively specified by the Nuclear power industry
| Model 1 | Model 3 | Model 4 | |
|---|---|---|---|
| Graphite Purity – % | 98 | 99 | 99.85 |
| Ash Content – % | 2 | 1 | 0.15 |
| Density Range – g/cm³ | 1.4-1.8 | 1.4-1.8 | 1.4-1.8 |
| Sulphur Content – ppm | ≤300 | ≤300 | ≤300 |
| Chloride Content – ppm | ≤25 | ≤10 | ≤10 |
| Fluoride Content – ppm | ≤25 | ≤10 | ≤10 |
| Halogen Content – ppm | ≤100 | ≤50 | ≤50 |
| Oxidation rate in air at 670⁰C – %/hour | <5 | <4 | <4 |
| Passive corrosion inhibitor | Yes | Yes | Yes |
Valve Stem Duties
- Maximum Operating Temperature
- Steam : +650⁰C Oxidising : +500⁰C Non-Oxidising : +1000⁰C
- Minimum Operating Temperature -200⁰C
- Maximum system Pressure : 250 bar
Typical Applications
- Valves and rotary equipment handling virtually any media
- High temperature steam
- Heat transfer media
- Petroleum products
- Demineralised water
- Inorganic and organic acids and alkalis, hot waxes and oils
Material Properties
- Compatible with media in the range pH 0-14
- No loss of volatiles at high temperature
- Lower limiting temperatures apply when used with oxidising agents
- Thermal conductivity, ring of density 1.4g/cm³ : Axial 400W/mK : Radial 6W/mK
- Coefficient of friction to steel : 0.05
Main features
- Outstanding sealing performance over long adjustment-free periods
- Excellent chemical resistance
- Very wide temperature range
Model 5
These rings use the 98% graphite purity of Model 1 but with the addition of a special low friction coating which has been sinter bonded to the graphite before the moulding process which helps ensure maximum service life.| Model 5 | |
|---|---|
| Graphite Purity – % | 98 |
| Ash Content – % | 2 |
| Density Range – g/cm³ | 1.4-1.8 |
| Sulphur Content – ppm | ≤300 |
| Chloride Content – ppm | ≤25 |
| Fluoride Content – ppm | ≤25 |
| Halogen Content – ppm | ≤100 |
| Oxidation rate in air at 670⁰C – %/hour | <5 |
| Passive corrosion inhibitor | Yes |
Valve Stem Duties
- Maximum Operating Temperature +350⁰C
- Minimum Operating Temperature -200⁰C
- Maximum system Pressure : 250 bar
Typical Applications
- Valves that handle dry gases and other fluids where friction on standard graphite seals is unacceptably high.
- Valves that suffer judder, hesitation or erratic action due to carbon pick-up or high-spot friction on the spindle
Material Properties
- Compatible with media in the range pH 0-14
- No loss of volatiles at high temperature
- Lower limiting temperatures apply when used with oxidising agents
- In comparative tests Model 5 displayed exactly half the friction coefficient of standard graphite and provided a continued low friction performance over more than 300 cycles
Main features
- Greatly reduces the torque needed for efficient valve action
- Saves on power consumption and enables smaller actuators to be used
- Lowers the break out friction for smoother valve operation
- Retains exceptionally low friction characteristics for up to 20,000 valve cycles
- Subsequent manual adjustment extends performance to 60,000 cycles
- Fire-safe capability enables rings to be used in plant subjected to fire rating tests
