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Choosing the correct oil seal application

Choosing and using the proper sealing devices within oil and gas applications can be vital when preventing dirt, dust, water, and other debris from potentially getting inside and contaminating products.  Of course, all rubber materials and seals will provide a range...

Nitrile rubber, NBR, and Buna-N – how well do you know your o ring materials?

A widely used elastomer, Nitrile, Buna-N, or NBR rubber, are all oil and fuel resistant and provide a great level of strength, making them a popular material for seals across various industries.  Suitable for a range of applications, this versatile rubber material,...

Optimum squeezing force for an o ring

It is true that the more squeeze you place on an o ring, the tighter the seal it will provide. In essence, the more squeeze (compression) you apply, the greater the force between the o ring and its mating hardware.  And ensuring you have the perfect seal is all...

O Ring Squeeze

The squeeze and shrinkage on an o ring are vital to understanding as these factors stand in the way of your application either experiencing a perfect seal or your application suffering from leaks.  You can measure the shrinkage of an o ring during...

Keeping your o rings bonded

EMI o rings. Those seal ring gaskets are made of silicone compounds, combining environmental sealing with electromagnetic interference protection.  Consisting of metal or metal-coated particles, silicone o rings are filled with silver, silver aluminium, or nickel...

The importance of mechanical seals when reducing water consumption in mining

Environmental considerations are at the top of most industry's agendas in the 21st century as companies evaluate and improve operations, processes, and systems.  Conserving water in mining is one such area that is now being investigated further with the rotation of...

How choosing the correct gasket reduces risks

Health and Safety across any industry are vital, especially so in industrial facilities and settings.  Why?  Because harmful leaks and emissions must be avoided at all costs to avoid serious accidents or injury to your teams and property.  That’s why having the right...

How to tighten your bolts perfectly

How to tighten your bolts and which tools you should use to achieve the perfect seal is not as seamless and straightforward as we would like. Various factors come into play in these situations, such as bolt grade, size, and even application type.  Tightening torques...

Static and Dynamic o rings

A range of factors and application dynamics come into play when choosing a particular type of o ring.  You need to understand the type of seal exert you require, the dimensions, and even compounds.  Due to the nature of an o ring and its overall design, o rings use...

Gasket Sealants

Fortunately, no one gasket suits a range of applications, but rather we have a multitude of gasket sealants available to meet various specifications and requirements.  Ultimately, sealants are used to effectively ensure gasket seals.  Helping to extend a gasket's life...

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 fillersGraphite 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 
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