The differences in the operating conditions of rubber parts of mechanical seals made of different materials ?

Some new customers, when consulting the sales department of ATACH about the selection of mechanical seals for pumps, often say that they should provide us with the best quality mechanical seals because they are not very familiar with mechanical seals. 

In fact, this statement is not accurate. Each type of mechanical seal made of different materials has its suitable working conditions. 

Even the very cheap nitrile rubber performs well when used in oily media. The technical department of ATACH Pump Industry now analyzes as follows:

The selection of rubber material in mechanical seals needs to be matched according to specific working conditions (such as medium type, temperature, pressure, etc.).

The following are the differences in the usage conditions of common rubber materials:

Nitrile rubber (NBR)

Applicable media: Mineral oil, fuel, lubricating oil and other oily media.

Temperature range: -40°C to 100°C (high-performance grades can reach 120°C).

Limitations: Not resistant to high temperatures, strong oxidants or steam environments, and has limited dynamic sealing performance. 

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Fluororubber (FKM)

Applicable media: Strong acids, strong alkalis, organic solvents and high-temperature oils.

Temperature range: -20°C to 250°C (short-term up to 300°C).

Limitation: Long-term exposure to steam or hot water can cause expansion and hardening, and the low-temperature performance is poor. 

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Ethylene Propylene diene monomer (EPDM)

Applicable media: water, steam, weak acid/alkali and ozone environment.

Temperature range: -40°C to 150°C.

Limitations: Not resistant to oil/fuel, and the dynamic sealing performance is average. 

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Chloroprene rubber (CR)

Applicable medium: weak acids, alkalis and some solvents.

Temperature range: -40°C to 120°C.

Limitations: Not resistant to oil/fuel, poor wear resistance, and not suitable for high dynamic stress environments. 

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Silicone rubber (VMQ)

Applicable medium: Food and pharmaceutical industries (oil-free/solvent-free environment).

Temperature range: -55°C to 220°C.

Limitations: Low mechanical strength, not resistant to oil, concentrated acids or solvents. ‌

Fluorosilicone rubber

Applicable media: oxygenated compounds, aromatic hydrocarbon solvents and brake fluid.

Temperature range: -50°C to 200°C.

Restriction: Avoid contact with ketone solvents. ‌

Other rubbers (natural rubber, styrene-butadiene rubber, etc.)

Natural rubber (NR) : It is suitable for non-oil media such as clear water and air, but it is not resistant to ozone or oil. ‌

Styrene-butadiene rubber (SBR) : It has good wear resistance but poor elasticity and is suitable for static sealing. ‌

Selection suggestions

 medium preference ‌ : for oily environments, select NBR or FKM; For water/steam environments, choose EPDM or silicone rubber.

 Temperature matching ‌ : fluororubber is preferred for high-temperature working conditions (>150°C); Special modified materials are required in low-temperature environments (<-20°C).

 dynamic/static requirements ‌ : Dynamic sealing (such as rotating parts) requires highly elastic materials (such as FKM); Static sealing can be selected from EPDM or NBR. ‌