By Published On: February 23, 2021Categories: Case Studies, Industrial Compressors0 Comments


Air compressors used in heavy vehicle braking systems were short-lived due to unanticipated side loading and subsequent internal damage.


System Seals re-designed the pistons to incorporate specialized bushings that resist side loads in high temperatures, while being able to retrofit into existing compressors.


Extensive testing proved the new design to be more than effective and could be easily adapted to existing parts, saving the company millions of dollars in replacement costs.

The world’s leading producer of braking systems for commercial vehicles recognized a serious problem when their brake compressors began to fail well within the warranty life. As a critical safety component on heavy trucks and buses, the company had more than 100,000 compressors on the road.

The issue stemmed from unanticipated side loading during the discharge of pressurized air. The running clearance between the steel piston and the aluminum housing was about 2/1000th of an inch – so tight that even minor deflections caused the metals to scrape against one another. The ensuing damage caused the O-rings to prematurely wear away, and eventually the compressors began to fail.

System Seals engineers took a close look at the design and determined that two very small L-shaped bushing were needed between the piston and housing to properly resist the side loads. Because the design used no lubricant, the bushings needed to be highly abrasion resistant and withstand temperatures above 400°F.

Inside the System Seals’ research and development lab, engineers experimented with a wide range of designs. In the end, they determined that a combination of materials worked best. One bushing was composed of molded PEEK – a semi-crystalline thermoplastic with excellent mechanical and chemical resistance properties that are retained in high temperatures. The second bushing was a precision machined Teflon composition with a polymer filler.

The company tested the new bushings for more than six months, and the design far exceeded their expectations. Moreover, existing compressors could be easily modified to accept the new bushings, which eliminated the need to replace the entire component.

The company created full rebuild kits for the troubled parts and later showcased the new design to major vehicle manufacturers as a key selling point. System Seals continues to produce the parts for the OEM to this day, and the compressors have long outlasted their warranties.

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