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Popular Types of Pneumatic Seals

01

Rod Seals

  • Sit around the moving rod.

  • Prevent air inside the cylinder from escaping past the rod.

02

Piston Seals

  • Fit into a groove on the piston itself.

  • Keep pressure on one side so the piston moves with force.

03

Wiper (Scraper) Seals

  • Also called dust seals.

  • Wipe away dirt, water, or metal chips from the rod as it retracts.

04

Cushion Seals

  • Located near end caps.

  • Absorb impact when the piston hits the end of its stroke.

05

. Rotary Pneumatic Seals

  • Used in swivel joints or rotary actuators.

  • Must resist both pressure and rotation.

Pneumatic Seals

Pneumatic seals keep compressed air where it belongs.

  • A bad seal can waste up to 30 % of system energy.

  • India is now among the top five sources of standard and custom pneumatic seals worldwide.

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What Are Pneumatic Seals?

Pneumatic seals are thin rings—often rubber, polyurethane, or PTFE—that sit inside cylinders, valves, or fittings to block compressed air from leaking. When the seal presses against metal walls, it creates an air-tight barrier so the piston or rod can move smoothly without losing pressure.

Why Do Pneumatic Seals Matter?

  1. Energy Savings: Leaks force compressors to run longer, driving up electric bills.

  2. System Accuracy: Pressure loss causes slow or uneven movement in tools and machines.

  3. Safety: Sudden pressure drops can slam actuators or create unexpected motion.

  4. Longevity: Good sealing reduces friction, wear, and heat, extending equipment life.
     

Internal link: If you work with hydraulic systems too, see our separate guide to hydraulic seals.

The Science Behind a Good Pneumatic Seal

Factor

Compression Set

Friction

Permeability

Durometer (Hardness)

Temperature Range

Temperature Range

Ability of material to return to its shape after squeezing

Resistance during movement

Rate at which gas passes through

Firmness measured on Shore A scale

How hot or cold the seal can get without failing

Strengths

Lower numbers mean the seal bounces back better

Less friction = less heat & wear

Lower is better to keep air inside

60 – 90 Shore A is common for air cylinders

Match this to your working environment

Quick Comparison Chart

Seal Type

Rod

Piston

Wiper

Cushion

Rotary

Motion

Linear

Linear

Linear

Linear

Rotational

Pressure Range (bar)

up to 10

up to 12

atmospheric

up to 10

up to 8

Common Material

Nitrile

Polyurethane

NBR / PU

NBR

PTFE

Common Material

2–5 years

2–6 years

1–3 years

3–4 years

1–2 years

*Typical industrial duty cycle, varies by maintenance & load.

Materials Commonly Used

NBR (Nitrile Butadiene Rubber)

  1. NBR (Nitrile Butadiene Rubber)

  • Good for general use, low cost.

  • Temperature: –30 °C to +100 °C.

    2. Polyurethane (PU)

  • High wear resistance, low compression set.

  • Handles shocks well; common in mobile equipment.

    3.  Silicone

  • Excellent for extreme cold or heat (–60 °C to +200 °C).

  • Softer, so less suited for high pressure.

   4.  PTFE (Polytetrafluoroethylene)

  • Very low friction, wide chemical compatibility.

  • Often bonded to rubber energizers to improve elasticity.

   5.  FKM (Fluorocarbon/Viton)

  • For oils, fuels, or solvents that might contact the seal.Higher price, but needed in harsh chemical zones.

How to Select the Right Pneumatic Seal

  1. Check System Pressure

  • Typical shop air runs 6–8 bar. If you go above 10 bar, pick a high-strength material like PU.

    2 . Consider Temperature

  • Outdoor cranes in winter? Look at silicone or special low-temp NBR.

  • Foundry lines? Choose FKM or high-heat silicone.

    3.  Measure Speed

  • Fast-moving pistons (> 1 m/s) need low friction PTFE or a hybrid seal to avoid heat build-up.

   4.  Match Groove Dimensions

  • Even the best seal fails if the groove is too wide or shallow. Follow ISO 5597 or manufacturer’s guide.

  5.   Media Compatibility

  • Oil mist lubrication? Check chemical tables.

  • Dry, oil-free air? Make sure the seal does not rely on oil for lubrication.

  6.   Regulatory Requirements

  • Food processing may call for FDA-compliant silicone or PTFE.

  • Pharmaceutical plants often need free of carbon black fillers.

Medical Diaphragms

In the medical field, diaphragms serve several important functions, from contraception to medical device components.

Medical Device Components

Many medical devices rely on diaphragms for proper function:

Blood pressure monitors use diaphragms in their pressure sensing mechanisms to provide accurate readings. The diaphragm responds to pressure changes in the cuff and converts them to readable measurements.

Respiratory equipment often incorporates diaphragms in valves and pressure regulators to ensure proper air flow and pressure delivery to patients.

Drug delivery systems may use diaphragms in pumps and dispensing mechanisms to control medication dosing accurately.

Contraceptive Diaphragms

Barrier contraceptive diaphragms are dome-shaped devices made from silicone or latex. They fit inside the vagina to cover the cervix, preventing sperm from reaching the egg. Modern contraceptive diaphragms are:

  • Reusable: Can be used for up to two years with proper care

  • Hormone-free: Provide contraception without hormonal side effects

  • Reversible: Fertility returns immediately after stopping use

  • Safe: Low risk of side effects when used correctly

Proper fitting and use:

  • Must be fitted by a healthcare provider initially

  • Should be used with spermicide for maximum effectiveness

  • Must remain in place for at least 6 hours after intercourse

  • Requires cleaning and proper storage between uses

Industrial Applications

Industries rely heavily on diaphragms for various applications, from simple controls to complex manufacturing processes.

Automotive Industry

Modern vehicles contain numerous diaphragms in different systems:

Brake systems use diaphragms in brake boosters to multiply the force applied to the brake pedal, making it easier to stop the vehicle safely.
 

Engine management systems incorporate diaphragms in vacuum controls, emissions systems, and fuel pressure regulators to ensure optimal engine performance.
 

Climate control systems use diaphragms in actuators that control air flow direction and temperature mixing.

Manufacturing and Process Control

Industrial manufacturing processes often require precise control of pressure, flow, and separation, making diaphragms essential components.

Pneumatic controls use diaphragms to convert air pressure into mechanical movement, operating everything from simple on/off valves to complex positioning systems.

Chemical processing equipment relies on diaphragms to separate different chemicals while allowing pressure transmission, ensuring safe and effective processing.

Water treatment facilities use diaphragm pumps and valves to move and control water flow through various treatment stages.

HVAC Systems

Heating, ventilation, and air conditioning systems use diaphragms in multiple ways:

  • Pressure switches that turn equipment on and off based on system pressure

  • Zone control dampers that direct airflow to different areas

  • Safety switches that shut down equipment if pressure becomes unsafe

  • Flow sensors that monitor air or water movement through the system

Materials Used in Diaphragm Manufacturing

The choice of material for diaphragm construction depends on the specific application requirements.

Rubber and Elastomers

Natural rubber provides excellent flexibility and is cost-effective for many applications. However, it has limitations in chemical resistance and temperature range.

Synthetic rubbers like EPDM, Nitrile, and Viton offer improved chemical resistance and temperature stability compared to natural rubber. Each type has specific strengths:

  • EPDM: Excellent weather resistance and electrical properties

  • Nitrile: Good oil and fuel resistance

  • Viton: Superior chemical resistance and high temperature capability

Thermoplastic Materials

Polyurethane diaphragms offer excellent abrasion resistance and can handle high pressures. They're often used in demanding industrial applications.

PTFE (Teflon) provides unmatched chemical resistance and can operate at extreme temperatures, making it ideal for harsh chemical environments.

Fabric-Reinforced Materials

Some diaphragms combine rubber or plastic with fabric reinforcement to provide additional strength and durability. These materials are often used in large diaphragms or high-pressure applications.

Metal Diaphragms

For extreme conditions, metal diaphragms made from stainless steel, titanium, or other alloys provide superior strength, temperature resistance, and longevity. They're commonly used in aerospace, high-pressure, and high-temperature applications.

Diaphragms continue to be essential components across many industries, and their importance will likely grow as technology advances. Whether in medical devices, industrial equipment, or everyday appliances, these simple yet effective components play crucial roles in our modern world. Understanding their types, applications, and proper care helps ensure they continue to serve us reliably for years to come.

Ready to learn more about diaphragms for your specific application? Contact a qualified engineer or supplier who can help you select the right diaphragm for your needs and ensure proper installation and maintenance.

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