Question 1

What are the common materials for O-rings?

Accepted Answer

The five most common O-ring materials are NBR (Nitrile) for oil and hydraulics, FKM (Viton) for high temperature and chemicals, EPDM for water and steam, VMQ (Silicone) for food and medical applications, and PTFE for extreme chemical resistance.

Question 2

What are the temperature limits for different O-ring compounds?

Accepted Answer

NBR operates from -40°C to +120°C. FKM from -20°C to +200°C. EPDM from -50°C to +150°C. VMQ from -60°C to +230°C. PTFE handles -200°C to +260°C but lacks elastomeric recovery.

Question 3

How do I choose the right O-ring material for chemical resistance?

Accepted Answer

Start by identifying every chemical the seal will contact, including additives and cleaning agents. Match the fluid to the elastomer using a chemical compatibility chart or tool. When in doubt, conduct an ASTM D471 immersion test.

Question 4

Can I use the same material for every O-ring in my facility?

Accepted Answer

No. A single material cannot cover all fluids and temperatures. Facilities typically stock NBR for general hydraulics, FKM for high-temperature service, and EPDM or VMQ for water and food equipment.

Question 5

What hardness should I specify?

Accepted Answer

70 Shore A is the standard general-purpose hardness. Use 80-90 Shore A for high-pressure or abrasive applications. Use 50-60 Shore A for low-pressure pneumatic or vacuum seals where conformability is critical.

Material Selector

Recommended Material: Nitrile Butadiene Rubber