How Do I Know If My Pneumatic Seals Need Replacing?

However, pneumatic seals will eventually become worn or damaged like any other component. To avoid compromising the performance of your pneumatic system, you need to know what signs to look for if you think your seals might need replacing.

What Makes A Pneumatic Seal?

Pneumatic seals come in various materials, sizes and shapes, depending on the application. Traditionally, most seals were made of pure rubber, but this is gradually giving way to synthetic rubber composites. Natural rubber offers high tensile strength, low odour, and greater resistance to tearing and fatigue, but it’s a limited source material that doesn’t age well. Natural rubber suffers when exposed to light, heat and ozone, and its natural proteins can act as allergens on human skin.

Synthetic rubber is made of chemical compounds designed to imitate the properties of natural rubber. It’s typically more resistant to abrasion, electrical heat, ozone, fluids, chemicals and ageing. Many varieties are also flame-resistant, which makes them useful in insulating electrical equipment. Synthetic rubber is resistant to oil and grease and stays flexible at low temperatures, so it’s a good choice for applications in extreme or hazardous environments.

Both natural and synthetic rubber seals have their place, depending on your application, your budget and the performance characteristics you require. Their durability and longevity will vary, so it’s important to know what’s the best type for your needs. 

When Your Pneumatic Seals Need Replacing

As part of your scheduled preventive maintenance, you should check seals regularly for any signs they might need replacement.

Air Leakage

Air leaks are the most obvious indication that your pneumatic seals need replacing. Leaks can be internal or external, occurring in such places as couplings, joints, fittings and the seals themselves. You’ll also find them cropping up in hoses and tubes and in areas where the packing is worn. You can usually hear an air leak hissing, but sometimes the sound might be masked by other noises, or the leak might be hidden. Another indicator of leaks is your system pressure dropping.

Contamination

Thorough cleaning of debris from your system is essential, including around the seals. This should be part of your preventive maintenance programme. This is because any contamination such as dust, dirt or other debris can damage seals and lead to failure. 

Wear And Tear

Pneumatic seals are always prone to wear and tear, especially if they’re exposed to harsh operating conditions. They’ll be affected by chemicals and high temperatures, which will eventually cause damage. If you see any damage to your pneumatic seals such as deformations, tears or cracks, you should always replace them.

Extreme Temperature

The usual range of temperatures pneumatic seals can withstand is -4°F to +176°F. Outside these limits, seals become brittle and crack and are susceptible to failure. When determining what material you need for your seals, it’s critical to ensure they can handle your pneumatic cylinder’s working temperature range.

Reduced Performance

Another way to know if your pneumatic seals need replacing is a drop in overall performance. Reduced performance could mean that your seals aren’t functioning properly any more. Your system might be taking longer to respond, or demonstrating a loss of power. This would be apparent in the cylinder moving too slowly, weakly or erratically. 

Age

Pneumatic seals have a limited lifespan, depending on their quality, system operating conditions and how well you maintain them. You should replace them every two or three years, or earlier if you perceive any of the signs that replacement is necessary.

General Maintenance For Pneumatic Seals

The are a few important points to note as far as general maintenance and pneumatic repair procedures:

• For safety, always turn off the power supply before beginning any maintenance. Compressed air can be dangerous, so ensure that any air remaining in the system is expelled into the atmosphere.

• Carefully check the areas most susceptible to damage or wear, including the cylinder tube, rod surface and rod seal. Replace any components that are worn or damaged, including the cylinder itself. 

• Thoroughly clean and lubricate the seals and any other parts or components that need lubrication. In a pneumatic cylinder assembly, you’ll need to lubricate the inner and outer surfaces of the piston seal, the piston seal groove, the rod seal and its groove on the rod cover. You should also pay attention to the tube gaskets and inner surface, plus the piston rod surface and outer surface of the piston itself.

Replacing Your Pneumatic Seals

When you discover worn, cracked, or leaking seals, you’ll have to set about replacing them. To do this, you’ll need to hold the cylinder tube cover securely in place in a vice before loosening and removing the rod cover with a monkey wrench or spanner.

• Remove each part of the cylinder carefully, and remove any grease or debris from each component with a clean cloth. Lay all the parts out in a recognisable order on a large, clean surface. 

• Pick out the old or worn seals and replace them with new ones, making sure you install them securely. When you put the cylinder back together, make sure the tube cover is slightly tighter than it was before.

• Once you’ve completed all these steps, turn the power back on and give the cylinder a small amount of operating pressure. Carry out all your usual tests for leakage and functionality, and reinstall the cylinder in your system only when you’re sure it’s leak-free and functioning properly. 

Once you’re fully aware of the importance of pneumatic seals, checking them becomes an automatic part of your preventive maintenance programme. Keep a weather eye out for leaks, pressure drops and other signs that seals need replacing, and your system will perform better and last longer.