Technical Design Data / Gaskets
Gaskets
Gasket Technology
The quality and performance of the gaskets is a crucial factor in the efficiency of any compression fit pipe joint. It is the gasket which absorbs the forces applied by the expansion and contraction of the pipes, the angular movements and even the weight of the pipe itself. To do this successfully, the gasket must retain its flexibility and compressive stress throughout its operational life.
Viking Johnson gaskets are made in accordance with BS EN 681 for water and BS EN 682 for gas, which specifies stringent requirements for physical and chemical properties, aimed at giving the best possible long-term performance.
Gasket Types
Fitted Gaskets
All straight couplings, stepped couplings and flange adaptors in the QuickFit, MegaFit, UltraGrip, Amplified UltraGrip, and MaxiFit products, are normally supplied ready-assembled with the gaskets already in position, making assembly of the product quicker and easier.
Removal of the gaskets prior to or during assembly of the coupling is neither necessary, nor recommended.
Unfitted Gaskets
Wedge-shaped gaskets are supplied as standard with Dedicated couplings, stepped couplings and flange adaptors in sizes DN350 and over. Unfitted gaskets are always stretched onto the pipe during installation.
Bonded Gaskets
Certain Viking Johnson products, such as EasiClamp, EasiTee, and HandiRange, are supplied with waffle type gaskets that are bonded into position, and these gaskets are not replaceable.
Gasket Grade Selection
Viking Johnson products offer a variety of gasket grades to suit the widest possible range of applications. To ensure maximum gasket life in the intended application, proper selection is essential.
Many factors need to be considered in deciding on the best grade for a specific service. Temperature is the primary consideration, with type and concentration of the product carried, duration and continuity of service also to be considered. Temperatures higher than the maximum quoted for each grade will lead to accelerated deterioration of the gaskets.
Fluctuating and / or Elevated Temperature
Whilst gasket compounds used in coupling type products may be capable of accommodating fluctuating or elevated temperatures (>60ºC) the relaxation rate of the elastomeric seals will increase, thus reducing the life expectancy of the joint. The failure mode is likely to be leakage of the seal between the coupling and pipe outside diameter, which, on the basis that there is sufficient travel on the bolts and the metal components are not touching, can be rectified by tightening the bolts. In the event that the metal components are touching, replacement of the gaskets in the coupling will be required
Standard Gaskets
Unless otherwise specified, Viking Johnson couplings are supplied with Grade E (EPDM) gaskets as standard in all sizes. Grade E is suitable for potable water, drainage and sewage applications but is NOT suitable for use with natural gas, hydrocarbon fuels and lubricants. For gas, oil and fuel applications Grade G (nitrile) should normally be specified.
| Grade E | Ethylene Propylene (EPDM) BS EN 681-1 water quality approved in various regions (e.g. UK WRAS approved). |
| Colour Flash | Green |
| Temperature Range | -40°C to +90°C (-40°F to 195°F) – (Note 1) |
| Suitable for | Potable water, sewage, many strong and oxidising chemicals, some food applications |
| NOT suitable for | Gas petroleum products, oily compressed air or hydrocarbon fuels and lubricants. |
| Products Available with Gasket | All Viking Johnson products have this grade as standard. |
| Grade G | Nitrile (NBR) BS EN 682 Type G. |
| Colour Flash | Silver |
| Temperature Range | -20°C to +100°C (-4°F to 212°F) – (Note 1) |
| Suitable for | Natural gas, petroleum products, low aromatic fuels (generally <30% aromatic content), oily compressed air and sewage applications |
| NOT suitable for | Potable water. |
| Products Available with Gasket | Viking Johnson Dedicated, Marine, QuickFit, MaxiFit, MegaFit, HandiRange, UltraGrip (DN40-400). |
Specialist Gaskets
| Grade V | Polychloroprene. |
| Colour Flash | Yellow |
| Temperature Range | -30°C to +90°C (-22°F to 195°F) – (Note 1) |
| Suitable for | Good resistance to ageing, weathering, ozone, oxidation, acids, most inorganic chemicals, vegetable and animal fats. Low flammability |
| NOT suitable for | Chlorinated hydrocarbons, aromatic solvents. |
| Products Available with Gasket | Viking Johnson Dedicated, Marine, QuickFit. |
| Grade C | Epichlorhydrin |
| Colour Flash | White with “ECO” superimposed |
| Temperature Range | -45°C to +110°C (-50°F to 230°F) – (Note 1) |
| Suitable for | Petroleum products, including low aromatic fuels (<30% aromatic content) and oily compressed air. |
| NOT suitable for | Aqueous media. |
| Products Available with Gasket | Viking Johnson Dedicated, Marine, QuickFit. |
| Grade A | Polyacrylis |
| Colour Flash | Purple |
| Temperature Range | -10°C to +130°C (15°F to 265°F) – (Note 1) |
| Suitable for | Hot transformer and lubricating oils, petroleum products and low aromatic fuels (<30% aromatic content). |
| NOT suitable for | Water and steam. |
| Products Available with Gasket | Viking Johnson Dedicated, Marine, QuickFit. |
| Grade O | Fluoroelastomer |
| Colour Flash | Blue |
| Temperature Range | -5°C to +180°C (25°F to 350°F) – (Note 1) |
| Suitable for | Petroleum products, aromatic fuels, hydraulic fluids, oxidising acids and organic liquids. |
| NOT suitable for | Ketones |
| Products Available with Gasket | Viking Johnson Dedicated, Marine, QuickFit. |
| Grade L | Silicone |
| Colour Flash | Red gasket material |
| Temperature Range | Dry Heat = -60°C to +200°C (-75°F to 390°F) – (Note 1) Wet Heat = -60°C to +120°C (-75°F to 245°F) – (Note 1) |
| Suitable for | Dry heat conditions, neutral aqueous and some chemical solutions. |
| NOT suitable for | Petroleum based products or high mechanical abuse applications. |
| Products Available with Gasket | Viking Johnson Dedicated, Marine, QuickFit. |
NOTE 1: Use on applications with fluctuating and / or elevated temperatures may require regular maintenance to re-tighten the bolts and must be included in any maintenance schedule.
NOTE 2: The above temperatures for each gasket type apply to the maximum rating of the gasket and not the finished product. See relevant technical datasheet for temperature rating of product.
Storage
Stored correctly, gaskets maintain full operational performance and maximum life expectancy. Please observe the following storage conditions.
- Store in a cool dark place and, where possible, in black polythene sacks which exclude light, especially ultra-violet.
- Store away from sunlight, electrical discharges and sparking electric motors.
- Storage temperature should be below 20°C (70°F) and preferably below 15°C (60°F).
- Always store gaskets in an unstressed condition – never hang on hooks, nails, handrails, etc., even for a short time.
Safety Note
Rubber gaskets should never be disposed of by burning, as harmful by-products can be produced. Never handle incinerated or fire damaged gaskets without proper protective clothing.
Lubrication
It is strongly recommended that unfitted gaskets are lubricated prior to fitting. Failure to apply lubricant can cause difficulty in fitting and may result in gasket creep under load. This may cause bolt torques to drop, thus necessitating re-tightening.
Renewal of Gaskets
If, for any reason, it becomes necessary to renew a gasket in a Viking Johnson dedicated coupling or flange adaptor (where the product cannot be fully dismantled and removed from the pipe), a strip of the correct section gasket material should be cut square about 6mm longer than the pipe circumference and inserted into the tapered recess of the sleeve. Care should be taken that the cut ends of the gasket butt together before bolting up the end rings – glueing the cut ends together prior to bolt-up may assist in this. Gasket strip can be purchased as strip from Viking Johnson.
NOTE: Reference should be made to the grade of gasket material required and coupling type. Alternatively, use a gasket of the same cross section but a larger diameter and cut this squarely to produce a strip sufficiently long to wrap around the pipe.