Gasket - materials
• The choice of rubber material depends on

– Fluids-chemical attack or not
– The combination of temperature and pressure

• Rubber materials change properties due to

– Time-the rubber relaxes
– Temperature-the rubber deteriorates
– Hardening by attack of oxidising agents(e.g., oxygen in air)
– Swelling or softening by absorption of chemicals in the fluids

• Common gasket types

– Nitrile – EPDM – FKM

• Nitrile (NBR)

• NBR (standard material) up to 110°C
• NBR-HT(hight temperature) up to 130°C

• NBR (FDA)-food grade for standard NBR

• NBR-HT(FDA)-food grade for high temperatures NBR

• NBR-LT-for low temperature inrefrigeration applications

 

•HNBR(hydrogenated) for duties where normal NBR swells and for higher temperatures up to 150°C, more expensive

–Resistant to :

Many hydrocarbons, fats, oils, greases, hydraulic fluids, sea water,chemicals.

–Attacked by :

Ozone (except PVC blends), ketones, esters, aldehydes, chlorinated and nitro hydrocarbons

 

• EDPM

• Standard material up to 150 °C

• EPDM (FDA)-food grade for EPDM.

–Resistant to :

Water, Animal and vegetable oils, ozone, strong and oxidizing chemicals.

–Attacked by :

Mineral oils and solvents, aromatic hydrocarbons.

• FKM, Fluorocarbon rubber

– Often called VITON (DuPont trade name) , used for aggressive chemical compounds

–Resistant to :

High temperature steam,aliphatic, aromatic and halogenated hydrocarbons, acids, animal and vegetable oils.

–Attacked by :

Ketones, low molecular weight esters and nitro containing compounds.

– Two different qualities usually used

• FKM A (VITON A)
• FKM G(VITON G) High performance and temperature resistance,much expensive than VITON A

Gasket - sealing lifetime

Product

• Gasket material

• Fastening

– Glue or glue-free

– Type of glue

• Gasket geometry

• Gasket groove

• Alignment of plate pack

 

Duty

• Operating temperature

• Operating pressure

• Media

• Type of operation continuous / cyclic

• Cleaning methods & chemicals

• Opening frequency

 

• Maximum temperature in CAS and product manual,

for example,
– NBR up to 110°C

– EPDM up to150°C
Gives 1 year life time

When no chemical attack takes place
• Rule of thumb:

– 10°C lower than max temperature,more than one years life time
– 10°C above the max temperature,6 months life time