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James Walker® Gaskets & Jointings > James Walkers’s advice on gasket use



  James Walkers’s advice on gasket use
 
The following information is provided for general guidance only.
YES . . .
• Ensure that gasket is compatible with the media at required operating temperature and pressure ranges, and is of the correct dimensions for the flange being sealed.
• Use gasket material and bolt grades that suit the tensile loading requirements of the flange.
• Specify the thinnest gasket that will suit the flange finish and parallelism.
• When appropriate, use an anti-stick coated gasket where joints are frequently replaced for operational reasons.
• Ensure the flange is clean, undamaged and without radial scores, free from oil and grease, and has the correct surface finish.
• Remove all traces of protective material before assembling the gasket.
• Ensure a cut gasket is free from burrs or ridges at bolt holes and edges to avoid uneven stress loading.
• Lubricate bolts and ensure that nuts can run freely down the threads before use.
• Use RotaBolts® on all important joints where unreliability may have a cost, health and safety or environmental impact.
• Tighten down the gasket evenly in several stages using an approved bolting sequence. This will avoid flange distortion and give even stressdistribution throughout the gasket.
• Use feeler gauges to check any predetermined degree of compression that is needed. This often applies to cork-elastomer gaskets.
• Non-metallic gaskets should always be stored flat, at a moderate temperature (ie, 15°C to 20°C), in dry conditions, away from direct sunlight and heat, and remote from ectrical equipment that may produce ozone.
NO . . .
• Never re-use an old gasket.
• Do not use low quality gaskets or jointings. Any
initial cost saving will soon be lost in plant
downtime and production delays caused by joint
failures.
• Do not use sealing compounds or grease on joints.
They reduce the friction between gasket and
flange which can allow a gasket to stress-relax
and creep, leading to premature failure.
•Avoid using impact adhesive or pressure sensitive
tapes at temperatures exceeding 40°C. Above this
temperature the tackifying resins may melt and act
as a lubricant.
• Do not mate flange faces that have different
surface finishes.
• Do not retighten bolts after use at elevated
temperatures on flanges sealed with gaskets of
compressed non-asbestos fibre.
 
SEATING STRESS GUIDE FOR GASKET SELECTION
Material Minimum operational stress (N/mm2) Maximum initial stress (N/mm2)
Compressed non-asbestos fibre 15 50
Fluolion® Integra Blue 13 50
Fluolion® Integra White 16 50
Supagraf® Plain Jointing 5 100
Supagraf® Tanged Jointing T10 6 150
Supagraf® Laminated Jointing S10 5 60
Metaflex® Spiral Wound + XA filler 35-45 *
Metaflex® Spiral Wound + SPG filler 30-40 *
Metakamm: Kammprofile Gaskets 25 200
Metcom Gaskets 20 100
Nebar® Red cork-elastomer jointing 1 10
Nebar® Brown cork-elastomer jointing 1 6
Gore-Tex GR® Style R 24 70
* Not applicable
NOTES:
1. All values shown are for guidance only.
2. The levels of sealability/gas tightness will depend upon the system pressure and media involved as well as actual operational stress.
3. Flange and bolt stiffness will affect the uniformity and level of stress applied, and hence sealing capability.
4. Each gasket type will show a different level of gas tightness at the minimum operational stress value given.
Also maximum leak tightness will be different for each gasket type.