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Official stockist for
James Walker Products

Graphite Products

STYLE A70
PURE EXPANDED FLEXIBLE MINERAL GRAPHITE HOMOGENEOUS GASKET SHEETS
(with inhibitor)

Style A70 has superior properties to asbestos, is a non-fibrous material and has none of the health or handling properties associated with asbestos. An environmentally friendly gasketing material with no binders or fillers, fire-safe and is non-toxic when in contact with foodstuffs and potable water.

Pure expanded mineral graphite flake or chip particles are subjected to laminar swelling and are subsequently calendered into flexible foil without the use of any separate binder, a feature which guarantees a high degree of purity not associated with other graphite derivatives. The foil is processed in a number of ways to adapt the unique properties of the material to a variety of sealing needs The raw material is a mineral that is mined in a similar way to coal.

Graphite lubricants and carbon components are no strangers to the sealing industry. Inherently low friction characteristics and excellent thermal properties are well established for such products. Style A70 combines these known advantages with two features vital to efficient, long term, static or dynamic sealing : - absence of volatile constituents and true resilience.

In short, the sealability of Style A70 is akin to that associated with elastomeric materials but its temperature capability far exceeds that of even the most exotic rubber compound. Add to this an outstanding resistance to a wide range of organic and inorganic chemicals and it is easy to see why many regard Style A70 as the most important addition to the seal manufacturer’s armoury since the advent of polytetrafluoroethylene (PTFE).

As frontiers of technology are pushed forward in a wide variety of industries, parallel advances must be made in sealing techniques to meet new conditions and more stringent performance demands.

The resources of Sampsons and the development of Style A70 combine the best service with a sophisticated approach to the sealing of flanges which bring many cost-effective benefits to the user.

TECHNICAL DATA
Purity / Sulphur Content max. ASTM C-816	98% / 700 ppm
Bulk Density ASTM C-559	1.0 to 1.1 g/cc
Ash Content ASTM C-561	Less than 0.5%
Leachable Chloride / Fluorides	50 ppm max. ASTM D-512
Temperature Range	-200°C to +3000°C (Non-Oxidising) -200°C to + 500°C (Oxidising) -200°C to + 650°C (Steam)
Tensile Strength / Stress Relaxation	998 psi / DIN 52913 - 48 N/mm²
Shore Hardness (D) / Creep Relaxation	30 / At 100°C ASTM F-38 < 5%
Sealability, ml/h Fuel A ASTM F-37B	<0.2 to 0.5
Electrical Resistance	900 x 10^-6 ohm cm parallel on surface 250,000 x 10^-6 ohm perpendicular to surface
Thermal Conductivity	120 Kcal/m. Hr.°C parallel to surface 4 Kcal/m Hr.°C perpendicular to surface
Coefficient of Thermal Expansion	5 x 10^-6 / °C parallel to surface 2 x 10^-6/ °C perpendicular to surface
Compressive Strength	more than 800 kg/cm²
Ignition Loss / Operating Pressure	less than 1% / 140 bar (2058 psi)
Resilient Rate / Density	more than 30% / 0.7 to 1.1 gr cm³
Compressibility ASTM F36A-66	40 to 45%
Recovery ASTM F36A-66	20 to 40%
ASTM ‘m’ facto	2
ASTM ‘y’ stress	1500 psi
Sliding-frictional Coefficient	0.149
pH range	0-14 chemically inert
Oxidation rate of exposed edge @ 500°C	0.03 to 0.4 g/m²/h

Table No.1
Compressibility / Recovery	Style A70
ASTM F36-66 Procedure H	1mm thk 2mm thk
(major load 7 N/mm²) (1000 lbf/in²)	1.0 g/cc
Compressibility	39% 33%
Recovery	20% 25%
Stress Relaxation DIN 52913	48 N/mm²
Creep Relaxation ASTM F-38 @ 100°C	<5%
Sealability Fuel A ASTM F-37B	<0.2 to 0.5 ml/

Table No. 1 is really the key to the performance gains available from Style A70 to be used as a flange gasket. If the material is contained in such a way that the volume of the seal does not diminish through mechanical problems such as extrusion, and no thermal/chemical degradation or abrasive wear takes place, the reduction in original sealing force is minimal, even after prolonged period of service. Although expanded graphite is more expensive than many conventional sealing materials, its selection will frequently be justified cost-effective even on a gasket by gasket basis due to the reduction in frequency of down time.

The quest for non-asbestos materials has shown that there are few, if any, alternatives to Style A70 which span the overall capabilities of, for example, compressed asbestos fibre. Where bolt loading is limited or the gasket shape is other than circular the choice will rest between plain Style A70 or the laminated versions described in Style SSR & TSR.

BASIC FACTS ABOUT Style A70

Good scratch resistance, ‘anti-stick’ treatment. No adhesion problems
No binders or filler, therefore no flow or creep under influence of temperature, pressure, chemicals or time exposure. No ageing or embrittlement.
Permanently resilient (10% of compressed gasket thickness)
Low friction properties - self lubricating, high thermal conductivity
Only a small quantities of adhesive thickness are used, the outstanding chemical resistance remains unaffected. Resistance to a wide range of chemicals.
No loss of volatiles even at high temperatures thus minimising frequency of gland adjustment.
Excellent resistance to compression set resulting in little loss of radial force or flange seating stress over long periods.
Unprecedented micro and macro sealing ability presents new way of sealing gasket surfaces that are out of flat, gouged or pitted.
High temperature capability particularly in non-oxidising environments. They are fire-proof !
Exceptionally low chloride content. Low permeability to gases and liquids.
Presents a non-wetting characteristic to glass, ceramics and most molten metals.
Sheets and laminates can be easily cut with conventional cutting or punching tools.
Standard and passivated expanded flexible mineral graphite conform to National Water Council requirements for service and potable water. Approval No. 7907 MX

Tables 2 & 3 show a typical leakage pressure against load curve for 1.0mm thick Style A70 sheet of 1.0 g/cc with nitrogen as the pressurising medium and the corresponding load/compression values. The recovery in thickness after the gasket has been removed from the flange assembly is indicative of the resilience of the material. Typical initial seating stress for optimum performance will be in the range 10-16 N/mm² of gasket area

Style A70 exhibits a high resistance to most agents including inorganic and organic acids and bases, solvents, hot waxes and oils. Exceptions are strong oxidising compounds such as concentrated nitric acid, highly concentrated sulphuric acid, chromium and permanganate solutions, chloric acid and molten alkaline and alkaline earth metals.

Please contact our sales office for further information

Disclaimer - The information contained herein is given in good faith. No liability will be accepted in relation to the same. Sampson Gaskets Limited exclude all conditions or warranties, express or implied as to their products and/or their fitness for any particular purpose

Unit 22, Leigh Road, Haine Industrial Estate,
Ramsgate, Kent CT12 5EU England

Telephone:
(01843) 854800
(08700) 349990

Fax:
(01843) 854801
(08700) 349991

Email:
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Export Sales -click here

News

16.04.2007
Sampson Gaskets relocate to new premises

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