Gasket Materials Guide
What follows is general guide to gasket materials: their properties and applications.
Let’s first of all divide gasket materials into a few broad categories: (Note 1 bar = 14 p.s.i or 100,000 newtons/sq. Metre)
1. Low pressures (less than a bar)
a) Temperatures below 100 centigrade (212 farenheit)
Simple lid or dust seals can utilise foam rubber.
If your application involves mineral oils only then consider paper or cork.
If there is water present or or some other liquid or gas look at rubber.
For food, electrical or chemicals you may need a special rubber or PTFE.
Or if you have good flanges and bolt loading then a solution may be non-asbestos jointing.
b) Temperatures above 100 centigrade (212 farenheit) and less than 220 centigrade (428 farenheit)
Consider Special Rubbers or PTFE.
Or if you have good flanges and bolt loading then look at non-asbestos gasket material.
2. High pressures and temperatures above 220 centigrade (428 farenheit)
a) Temperatures up to 450 centigrade (842 farenheit) but STEAM to 230 centigrade (446 farenheit)
First consider non-asbestos jointing.
If your application involves process cycling and steam look at graphite.
3. Special Applications
For temperatures above 450 centigrade with no oxygen present consider graphite.
If you have extreme temperatures but little pressure eg. turbochargers use mica.
Extreme conditions in pipework can be accommodated with spiral wound gaskets.
If you have a specific material requirement, you many require a food quality or pharmaceutical grade material.
Specifying Gasket Material By Function
The following table, which gives a useful guide to specifying gasket materials by their uses, might also be helpful:
|Anti Vibration||Rubber | Neoprene | Nitrile | Cork||Electronic | Electrical Motors | Industrial Plant Machinery | Automotive||Aerospace and Defence|
|Flame Retardant||Silicone Foam – UL94, HT-800, HT-6360 | FPC, Fireblock Material | EC 2130 (Flame rated EMI) | R10400M (Flame rated Silicone Foam||Residential and commercial lighting gaskets | Commercial Signage | Commercial cooking equipment and ventilation | Enclosure gaskets | Industrial Controls | Handheld Electronics | Rugged Cushion Pads | Flame rated EMI gaskets| Telecommunications Base Stations||FAR 25.83 – an FAA Flame test for aircraft interiors. Materials must be self-extinguishing under the vertical burn test|
|Dust||Poron® | Silicone Foam | Neoprene Foam||Clean Rooms | HEPA Filters | HVAC/air handling | LCD Displays | Touch Panel displays | Portable Electronics||Compression Cycling | Temperature | Outgassing | Cushioning | Test Requirements – Common testing for Dust applications include; NEMA Type 1, IP5X and IP6X (IP50 and IP60 have no water sealing requirements)|
|High Temperature||Rubber Materials – Urethane (less than 121⁰C) | Natural Rubber (less than 121⁰C) | Neoprene (less than 149⁰C) | Nitrile (less than 149⁰C)| EPDM (less than 204⁰C) | Fluorosilicone (204⁰C – 260⁰C) | Fluorocarbon (204⁰C-260⁰C) | Silicone (204⁰C-260⁰C) Higher Temperature Composite Materials – Non-asbestos jointing (Klinger Flexitallic etc;) | Ceramic Fibre (up to 1000⁰C) | Firefly (up to 1000⁰C) | Graphite (up to 450⁰C) | Metallic Gaskets (Spiral Wounds/Ring type joints)||Any application where heat is above ambient temperature. Composite gaskets and metallic considered when high temperatures and subsequent high pressure are involved||Heat aging is critical with rubber products as heat aging will gradually degrade all elastomers. The following testing all have heat aging requirements. ASTM D 1056 | ASTM D 573 | UL 50 | UL 48 | UL 508 | UL 157|
|FoodSafe, FDA, Antimicrobial||Platinum Cured Silicone | Silicone Rubber/Foam | EPDM (white/blue) | Natural Rubber (white) | PTFE | Nitrile (white) | WRAS approved EPDM (potable water) | WRAS approved Aramid Fibre | PTFE Sheet Jointing | Nitrile Sheet Jointing BS7531 Grade Y||Food Manufacturing | Food Processing Plants | Pharmaceutical Machinery | Clean rooms||Just because it is white or blue in colour doesn’t mean it is food safe. FDA approved materials and FoodSafe approved materials EU 19235:2004 | FDA 21 CFR | USP Class VI | NSF/ANSI Standard 51 | Mil-STD 810 | EN1186|
|Electrical||Nitrile Cork | Nebar Cork | Neoprene Cork | Polyethylene Foam | EPDM Foam | Silicone Rubber | EMI Shielding Rubber||Transformer gaskets | Oil and Water Tanks | IP rating (ingress protection)||IP Rating | NEMA | UL / IP rating | (See above Environmental Gasket Column)|